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Obstentrics_Williams. All sonography machines are required to display two indices: the thermal index and the mechanical index. The thermal index is a measure of the relative probability that the examination may raise the temperature, potentially high enough to induce injury. That said, fetal damage resulting from commercially available ultrasound equipment in routine practice is extremely unlikely. The potential for temperature elevation is higher with longer examination time and is greater near bone than in soft tissue. heoretical risks are higher during organogenesis than later in gestation. The thermal index for soft tissue, Tis, is used before 10 weeks' gestation, and that for bone, ib, is used at or beyond 10 weeks' (American Institute of Ultrasound in Medicine, 2013b). The thermal index is higher with pulsed Doppler applications than with routine B-mode scanning (p. 213). In the first trimester, if pulsed Doppler is clinically indicated, the thermal index should be ;0.7, and the exposure time should


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Obstentrics_Williams. Doppler applications than with routine B-mode scanning (p. 213). In the first trimester, if pulsed Doppler is clinically indicated, the thermal index should be ;0.7, and the exposure time should be as brief as possible (American Institute of Ultrasound in Medicine, 2016) . To document the embryonic or fetal heart rate, motion-mode (M-mode) imaging is used instead of pulsed Doppler imaging.


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Obstentrics_Williams. The mechanical index is a measure of the likelihood of adverse efects related to rarefactional pressure, such as cavi tationwhich is relevant only in tissues that contain air. Microbubble ultrasound contrast agents are not used in pregnancy for this reason. In mammalian tissues that do not contain gas bodies, no adverse efects have been reported over the range of diagnostically relevant exposures. Because fetuses cannot contain gas bodies, they are not considered at risk. The use of sonography for any nonmedical purpose, such as "keepsake fetal imaging," is considered contray to responsible medical practice and is not condoned by the Food and Drug Administration (2014), the American Institute of Ultrasound in Medicine (2012, 2013b), or the American College ofObstetricians and Gynecologists (2016).


Obstentrics_Williams

Obstentrics_Williams. The reported prevalence of work-related musculoskeletal discomfort or injury among sonographers approximates 70 percent Ganga, 2012; Roll, 2012). The main risk factors for injury during transabdominal ultrasound examinations are awkward posture, sustained static forces, and various pinch grips used while maneuvering the transducer (Centers for Disease Control and Prevention, 2006). Maternal habitus can be contributory because more force is oten employed when imaging obese patients. The following guidelines may help avert injury: 1. Position the patient close to you on the examination table. As a result, your elbow is close to your body, shoulder abduction is less than 30 degrees, and your thumb is facing up. 2. Adjust the table or chair height so that your forearm is parallel to the floor. 3. If seated, use a chair with back support, support your feet, and keep ankles in neutral position. Do not lean toward the patient or monitor. 4.


Obstentrics_Williams

Obstentrics_Williams. 3. If seated, use a chair with back support, support your feet, and keep ankles in neutral position. Do not lean toward the patient or monitor. 4. Face the monitor squarely and position it so that it is viewed at a neutral angle, such as 15 degrees downward. 5. Avoid reaching, bending, or twisting while scanning. 6. Frequent breaks may prevent muscle strain. Stretching and strengthening exercises can be helpful. The earlier that sonography is performed, the more accurate the gestational age assessment. Specific criteria for "re-dating" a pregnancy, that is, reassigning the gestational age and estimated date of delivery using initial sonogram findings, are shown in Table 1 0-1. The only exception to revising the gestational age based on early sonography is if the pregnancy resulted from assisted reproductive technology, in which case accuracy of gestational age assessment is presumed.


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Obstentrics_Williams. Sonographic measurement of the crown-rump length (CRL) is the most accurate method to establish or conirm gestational TABLE 10-1. Sonographic Gestational Age Assessment Gestational Age Parameter(s) to Revisea 9 to <14 wks CRL 14 to <16 wks BPO, HC AC FL 16 to <22 wks BPO, HC AC FL >10 d 22 to <28 wks BPO, HC AC FL >14d :28 weeks BPOt HC AC FL >21 d aSonographic gestational age should be used when the LMP-derived gestational age differs from that obtained with sonography by the threshold value. abdominal circumference; BPO biparietal diameter; CRL = crown-rump length; FL = femur length; HC = head circumference; LMP = last menstrual period. Modified from American College of Obstetricians and Gynecologists,l2017b. FIGURE 10-1 The measured crown-rump length in this 12-week 3-day fetus approximates 6 cm.


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Obstentrics_Williams. FIGURE 10-1 The measured crown-rump length in this 12-week 3-day fetus approximates 6 cm. age (Appendix, p. 1263). As noted, transvaginal imaging typi cally yields higher resolution images. The CL is measured in the midsagittaleplane with the embryo or fetus in a neutral, nonlexed position so that its length can be measured in a straight line (Fig. The measurement should include neither the yolk sac nor a limb bud. The mean of three discrete measurements is used. Until 136/7 weeks' gestation, the CL is accurate to within 5 to 7 days (American College of Obstetricians and Gynecologists, 201 7b).


Obstentrics_Williams

Obstentrics_Williams. Starting at 14°/ weeks, equipment software formulas calculate estimated gestational age and fetal weight from measurements of the biparietal diameter, head and abdominal circumference, and femur length (Fig. 10-2). The estimates are most accurate when multiple parameters are used but may over-or underestimate fetal weight by up to 20 percent (American College of Obstetricians and Gynecologists, 2016). Various nomograms for other fetal structures, including the cerebellar diameter, ear length, ocular distances, thoracic circumference, and lengths of kidney, long bones, and feet, may be used to address speciic questions regarding organ system abnormalities or syndromes (Appendix, p. 1266).


Obstentrics_Williams

Obstentrics_Williams. The biparietal diameter (BPD) most accurately reflects gestational age, with a variation of 7 to 10 days in the second trimester. The BPD is measured perpendicular to the midline falx in the transthalamic view, at the level of the thalami and cavum septum pellucidum (CSP) (see Fig. 10-2A). Calipers are placed from the outer edge of the skull in the near ield to the inner edge of the skull in the far field. he head circumference (HC) is also measured in the trans thalamic view. An ellipse is


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-2 Fetal biometry. A. Transthalamic view. A transverse (axial) image of the head is obtained at the level of the cavum septum pellucidum (arrows) and thalami (asterisks). The biparietal diameter is measured perpendicular to the sagittal midline, from the outer edge of the skull in the near field to the inner edge of the skull in the far field. By convention, the near field is that which is closer to the sonographic transducer. The head circumference is measured circumferentially around the outer border of the skull. B. Femur length. The femur is measured perpendiCUlar to the femoral shaft, from each diaphyseal end, excluding the epiphysis. C. Abdominal circumference. This is a transverse measurement at the level of the stomach (5). The J-shaped structure (arrowheads) indicates the confluence of the umbilical vein and the right portal vein. Ideally, only one rib is visible on each side of the abdomen, indicating that the image was not taken at an oblique angle.


Obstentrics_Williams

Obstentrics_Williams. placed around the outer edge of the skull or the circumference is calculated using BPD and occipital-frontal diameter (OFD) values. he cephalic index, which is the BPD divided by the OFD, is normally 70 to 86 percent. If the head shape is lattened-dolichocephay, or roundedbrachycephay, the HC is more reliable than the BPD. hese head shape variants may be normal or can be secondary to fetal position or oligohydramnios. But, dolichocephaly can occur with neural-tube defects, and brachycephaly may be seen in fetuses with Down syndrome. lso, with abnormal skull shape, craniosynostosis and other craniofacial abnormalities are a consideration.


Obstentrics_Williams

Obstentrics_Williams. he femur length (FL) correlates well with both BPD and gestational age. It is measured with the beam perpendicular to the long axis of the shat. Calipers are placed at each end of the calcified diaphysis and exclude the epiphysis. For gestational age estimation, it has a variation of 7 to 11 days in the second trimester (see Fig. 1O-2B). A femur measurement that is <2.5th percentile for gestational age or that is shortened to :;90 percent of that expected based on the measured BPD is a minor marker for Down syndrome (Chap. 14, p.287). he normal range for the FL to abdominal circumference (AC) ratio is generally 20 to 24 percent. A dramatically foreshortened FL or a FL-to-AC ratio below 18 percent prompts evaluation for a skeletal dysplasia (p. 210).


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Obstentrics_Williams. Of biometric parameters, AC is most afected by fetal growth. Thus, for gestational age estimation, AC has the greatest variation, which can reach 2 to 3 weeks in the second trimester. To measure the AC, a circle is placed outside the fetal skin in a transverse image that contains the stomach and the confluence of the umbilical vein with the portal sinus (see Fig. 10-2C). The image should appear as round as possible and ideally contains no more than 1 rib on each side of the abdomen. he kidneys should not be visible in the image. Variability of the sonographic gestationl age estimate increases with advancing gestation. Accordingly, pregnancies not imaged prior to 22 weeks to conirm or revise gestational age are considered suboptimaly ated (American College of Obstetricians and Gynecologists, 2017a). Although the estimate is improved by averaging multiple parameters, if one parameter difers TABLE 10-2. Some Indications for First-Trimester Ultrasound Examination


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Obstentrics_Williams. TABLE 10-2. Some Indications for First-Trimester Ultrasound Examination Define the cause of vaginal bleeding Assist chorionic villus sampling, embryo transfer, and Assess for certain fetal anomalies, such as anencephaly, in a bnormaIities Measure nuchal translucency /hen part of a screening Modified from the American Institute of Ultrasound in significantly from the others, consideration should be given to excluding it from the calculation. he outlier may result from poor visibility, but it could also indicate a fetal abnormality or growth problem. Reference tables such as the one in the Appendix (p. 1264) may be used to estimate fetal weight percentiles.


Obstentrics_Williams

Obstentrics_Williams. Indications for sonography before 14 weeks' gestation are listed in Table 10-2. Early pregnancy can be evaluated using transabdominal or transvaginal sonography, or both. he components listed in Table 10-3 should be assessed. First-trimester sonography can reliably diagnose anembryonic gestation, embryonic demise, ectopic pregnancy, and gestational trophoblastic disease. he irst trimester is also the ideal time to evaluate the uterus, adnexa, and cul-de-sac. Determination of TABLE 10-3. Components of Standard Ultrasound Examination by Trimester Gestational sac size, location, and number Embryo and/or yolk sac identification Crown-rump length Fetal number, including amnionicity and chorionicity of the first rimester Evaluation of the maternal uterus, adnexa, and cul-de-sac Evaluat"on of the fetal nuchal region, with consideration of fetal :chal translucenry assessment Fetal number, including amnionicity and chorionicity of multifetal gestations


Obstentrics_Williams

Obstentrics_Williams. Fetal number, including amnionicity and chorionicity of multifetal gestations Placental location, appearance, and relationship to tie internal cervical os, with documentation of placental cord insertion site when technically possible Fetal anatomical survey, including documentation of technical limitations Evaluation of the maternal uterus, adnexa, and cervix when Modified from the American Institute of Ultrasound in Medicine, 2013a. chorionicity in a multifetal gestation is most accurate in the first trimester (Chap. 45, p. 868).


Obstentrics_Williams

Obstentrics_Williams. Modified from the American Institute of Ultrasound in Medicine, 2013a. chorionicity in a multifetal gestation is most accurate in the first trimester (Chap. 45, p. 868). n intrauterine gestational sac is reliably visualized with transvaginal sonography by 5 weeks, and an embryo with cardiac activity by 6 weeks (Fig. 10-3). The embryo should be visible transvaginally once the mean sac diameter has reached 25 mm-otherwise the gestation is anembyonic. Cardiac motion is usually visible with transvaginal imaging when the embryo length reaches 5 mm. In embryos <7 mm without cardiac activity, subsequent examination may be needed to determine viability (American College of Obstetricians and Gynecologists, 2016). At Parkland hospital, first-trimester demise is diagnosed if the embryo has reached 10 mm and lacks cardiac motion. Other criteria for this diagnosis are found in Chapter 18 (Table 18-3, p. 350).


Obstentrics_Williams

Obstentrics_Williams. Nuchal translucency (NT) evaluation is a component of first-trimester aneuploidy screening, discussed in Chapter 14 (p. 281). It represents the maximum thickness of the subcutaneous translucent area between the skin and soft tissue overlying the fetal spine at the back of the neck. NT is measured in the sagittal plane between 11 and 14 weeks' gestation using precise criteria (Table 10-4). When the NT measurement is increased, the risk for fetal aneuploidy and various structural anomalies-in particular heart defects-is signiicantly elevated.


Obstentrics_Williams

Obstentrics_Williams. Assessment for selected fetal abnormalities in an at-risk pregnancy is done with irst-trimester sonography (see Table 10-2). Research in this area has focused on anatomy visible at 11 to 14 weeks' gestation, to coincide with sonography performed as part of aneuploidy screening. ith current technoloy, it is not realistic to expect that all major abnomalities detectable in the second trimester may be visualized in the irst trimester. Thus, irst-trimester scanning should not replace second-trimester anatomical evaluation (American College of Obstetricians and Gynecologists, 2016). FIGURE 10-3 A. The measured crown-rump length is approximately 7 mm in this 6-week embryo. B. M-mode demonstrates embryonic cardiac activity and a heart rate of 124 beats per minute.


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Obstentrics_Williams. As examples, in one study of more than 40,000 pregnancies undergoing sonographic aneuploidy screening between 11 and 14 weeks, basic anatomical evaluation yielded a detection rate of approximately 40 percent for structural abnormalities (Syngelaki, 2011). Bromley and colleagues (2014) similarly found that late irst-trimester sonography identiied major abnormalities in 0.5 percent of pregnancies, representing approximately 40 percent of pregnancies with anomalies detected prenatally. Detection rates are very high for anencephaly, alobar holoprosencephaly, and ventral wall defects. But, in one analysis of more than 60,000 pregnancies with these early scans, only a third of major cardiac anomalies were identiied, and no cases of microcephaly, agenesis of the corpus callosum, cerebellar abnormalities, congenital pulmonary airway malformations, or bowel obstruction were detected (Syngelaki, 2011). In another study of low-risk or unselected pregnancies, 32 percent of anomalies were


Obstentrics_Williams

Obstentrics_Williams. abnormalities, congenital pulmonary airway malformations, or bowel obstruction were detected (Syngelaki, 2011). In another study of low-risk or unselected pregnancies, 32 percent of anomalies were detected, whereas in pregnancies described as high-risk, anomaly detection exceeded 60 percent (Karim, 2017).


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Obstentrics_Williams. It is recommended that sonography be routinely ofered to all pregnant women between 18 and 22 weeks' gestation (American TABLE 10-4. Guidelines for Nuchal Translucency (NT) Measurement The margins of NT edges must be clear enough for proper caliper placement The fetus must be in the midsagittal plane The image must be magnified so that it is filled by the fetal head, neck, and upper thorax The fetal neck must be in a neutral position, not flexed and not hyperextended The amnion must be seen as separate from the NT line Electronic calipers must be used to perform the measurement The + calipers must be placed on the inner borders of the nuchal space with none of the horizontal crossbar itself protruding into the space The calipers must be placed perpendicular to the long axis of the fetus The measurement must be obtained at the widest space of the NT From the American Institute of Ultrasound in Medicine, 20 13a, with permission.


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Obstentrics_Williams. From the American Institute of Ultrasound in Medicine, 20 13a, with permission. TABLE 10-5. Some Indications for Second-or ThirdTrimester Ultrasound Examination Preterm premature rupture of membranes and/or preterm labor Adjunct to cervical cerclage Adjunct to amniocentesis or other procedure Adjunct to external cephalic version Assessment for findings that raise the aneuploidy risk Follow-up evaluation of a fetal anomaly History of congenital anomaly in prior pregnancy Adapted from the American Institute of Ultrasound in Medicine,l201l3a.


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Obstentrics_Williams. Follow-up evaluation of a fetal anomaly History of congenital anomaly in prior pregnancy Adapted from the American Institute of Ultrasound in Medicine,l201l3a. College of Obstetricians and Gynecologists, 2016). This time interval permits accurate assessment of gestational age, fetal anatomy, placental location, and cervical length. Recognizing that the gestational age at which abnormalities are identified may afect pregnancy management options, providers may opt to perform the examination prior to 20 weeks. The many additional indications for second-and third-trimester sonography are listed in Table 10-5. The three examination types are standard, specialized-which includes targeted sonography, and limited.


Obstentrics_Williams

Obstentrics_Williams. The standard sonogram includes evaluation of fetal number and presentation, cardiac activity, amnionic fluid volume, placental position, fetal biometry, and fetal anatomy (American Institute of Ultrasound in Medicine, 2013b). When technically feasible, the maternal cervix and adnexa are examined as clinically appropriate. Components are found in Table 10-3, and the fetal anatomical structures that should be evaluated are listed in Table 10-6. With twins or other multiples, documentation also includes the number of chorions and amnions, comparison of fetal sizes, estimation of amnionic luid volume within each sac, and fetal sex determination (Chap. 45, p. 868).


Obstentrics_Williams

Obstentrics_Williams. he targeted sonogram is a type of specialized examination. It is performed when the risk for a fetal anatomical or genetic abnor mality is elevated because of history, screening test result, or abnor mal inding during standard examination (Table 10-7) . Targeted sonograms include a detailed anatomical survey, the components of which are shown in Table 10-6. Because it carries the CPT code 76811, this sonogram is colloquilly called the "76811 examina tion." It is intended to be indication-driven and should not be repeated later in the absence of an extenuating circumstance.


Obstentrics_Williams

Obstentrics_Williams. have expertise in fetal imaging, through both training and ongo ing experience (Wax, 2014). For many of the targeted examina tion components, the physician determines on a case-by-case basis whether assessment is needed (American College of Obstetricians and Gynecologists, 2016). Other types of specilized examinations include fetal echocardiography, Doppler evaluation, and the bio physical proile, which is described in Chapter 17 (p. 337). A limited sonogram is performed to address a speciic clini cal question. Examples include evaluation of fetal presentation, viability, amnionic luid volume, or placental location. In the absence of an emergency, a limited examination is only per formed if a standard sonogram has already been completed. Otherwise, provided that the gestational age is at least 18 weeks, a standard sonogram is recommended.


Obstentrics_Williams

Obstentrics_Williams. Otherwise, provided that the gestational age is at least 18 weeks, a standard sonogram is recommended. With current advances in imaging technology, approximately 50 percent of major fetal abnormalities overall are detected with standard sonography (Rydberg, 2017). he sensitivity of sonography for detecting fetal anomalies varies according to factors such as gestational age, maternal habitus, fetal position, equipment features, examination type, operator skill, and the speciic abnormality in question. For example, maternal obesity has been associated with a 20-percent reduction in the anomaly detection rate (Dashe, 2009). Detection also varies considerably according to the abnormality.


Obstentrics_Williams

Obstentrics_Williams. Detection also varies considerably according to the abnormality. For example, population-based data from 18 registries comprise the EUROCAT network. Between 2011 and 2015, EUROCAT (2017) prenatal detection rates for selected fetal anomaliesexcluding genetic conditions-were as follows: anencephaly, 99 percent; spina bifida, 89 percent; hydrocephaly, 78 percent; clet lip/palate, 68 percent; hypoplastic let heart, 87 percent; transposition of the great vessels, 64 percent; diaphragmatic hernia, 74 percent; gastroschisis, 94 percent; omphalocele, 92 percent; bilateral renal agenesis, 94 percent; posterior urethral valves, 79 percent; limb-reduction defects, 57 percent; and clubfoot, 57 percent.


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Obstentrics_Williams. Importantly, however, the overall anomaly detection rate, excluding aneuploidy, was below 40 percent. his relects inclusion of anomalies with minimal or no sonographic detection in the second trimester, such as microcephaly, choanal atresia, cleft palate, Hirschsprung disease, anal atresia, and congenital skin disorders. hese are mentioned because clinicians tend to focus on abnormalities amenable to sonographic detection, whereas those not readily detectable may be equally devastating to families. Therore, evey sonographic examination should include a frank discussion of examination limitations. Most anomalous neonates are born to women whose pregnancies are otherwise considered low-risk, that is, without an TABLE 10-6. Components of Standard and Targeted Fetal Anatomic Surveys Head, face, and neck Lateral cerebral ventricles Choroid plexus Midline falx Cavum septum pellucidum Cerebellum Cistena magna Upper lip Consideration of nuchal skin fold measurement at 15-20 weeks


Obstentrics_Williams

Obstentrics_Williams. Head, face, and neck Lateral cerebral ventricles Choroid plexus Midline falx Cavum septum pellucidum Cerebellum Cistena magna Upper lip Consideration of nuchal skin fold measurement at 15-20 weeks Four-chamber view of the heart Left ventricular outflow tract Right ventricular outflow tract Stomach: presence, size, and situs Cervical, thoracic, lumbar, and sacral spine Head, face, and neck Integrity and shape of cranium Third ventriclea Fourth ventriclea Corpus callosuma Cerebellar lobes, vermis Brain parenchyma Profile Coronal nose, lips, lensa Palatea, maxilla, mandible, and tonguea Ear pOSition and sizea Orbitsa Neck Integrity of diaphragm Abdomen Small and large bowela Adrenal glandsa Gallbladdera Liver Renal arteriesa Spleen° Integrity of abdominal wall Integrity of spine and overlying soft tissue Architecture, position, number Hands Digitsa: number, position aWhen medically indicated (determined on case-by-case basis).


Obstentrics_Williams

Obstentrics_Williams. Integrity of spine and overlying soft tissue Architecture, position, number Hands Digitsa: number, position aWhen medically indicated (determined on case-by-case basis). Modified from the American Institute of Ultrasound in Medicine, 2013a; Wax, 2014.


Obstentrics_Williams

Obstentrics_Williams. indication for targeted sonography. hus, for standard sonographic examinations, accurate documentation and quality assurance are essential to optimize detection rates. Practice guidelines and standards established by organizations such as the American Institute of Ultrasound in Medicine (2013b) and the Internationl Society of Ultrasound in Obstetrics and Gynecology (Salomon, 2011) have undoubtedly contributed to improvements in anomaly detection rates. Ultrasound practice accreditation is a process ofered by the American Institute of Ultrasound in Medicine and the American College of Radiology that was developed to improve imaging quality and adherence to guidelines. It includes review of images and their storage, ultrasound equipment, report generation, and the qualifications of physicians and sonographers. The Society for Maternal-Fetal Medicine (2013) recommends that whenever possible, obstetrical ultrasound examinations by maternal-fetal medicine sub specialists be performed by


Obstentrics_Williams

Obstentrics_Williams. and sonographers. The Society for Maternal-Fetal Medicine (2013) recommends that whenever possible, obstetrical ultrasound examinations by maternal-fetal medicine sub specialists be performed by accredited practices.


Obstentrics_Williams

Obstentrics_Williams. Evaluation of amnionic luid volume is a component of every second-or third-trimester sonogram, and volumes vary with TABLE 10-7. Indications for Targeted Fetal Anatomical Ultrasound Examination Prior fetus or neonate with a structural or genetic/chromosomal abnormality Current pregnancy with known or suspected fetal abnormality or confirmed growth abnormality Maternal diabetes diagnosed before 24 weeks' gestation Assisted repr0ductive technology to achieve conception Matenal prepregnancy body mass index >30 kg/m2 Multifetal gestation (Chap. 45, p. 864) Nuchal translucency measurement ::3.0 mm Parental carriage of genetic/chromosomal abnormality Maternal age ::35 at delivery Nuchal translucency measurement ::3.0 mm Other condition affecting the fetus Congenital infection (Chaps. 64 and 65) Alloimmunization (Chap. 15, p. 301) Amnionic fluid abnormality (Chap. 11l, p. 227) Modified from Jax, 2014, 2015.


Obstentrics_Williams

Obstentrics_Williams. Other condition affecting the fetus Congenital infection (Chaps. 64 and 65) Alloimmunization (Chap. 15, p. 301) Amnionic fluid abnormality (Chap. 11l, p. 227) Modified from Jax, 2014, 2015. gestational age. Oligohydramnios indicates an amnionic fluid volume below normal range, and subjective crowding of the fetus is often noted. Hydramnios-also calledpoyhydramniosdefines a volume above a given normal threshold. Amnionic luid volume is usually assessed semiquantitatively. Measurements include either the single deepest vertical luid pocket or the sum of the deepest vertical pockets from each of four equal uterine quadrants-the amnionic luid index (Phelan, 1987). Reference ranges have been established for both measurements from 16 weeks' gestation onward. he single deepest vertical pocket is normally between 2 and 8 cm, and the amnionic luid index normally ranges between 8 and 24 cm. A further discussion and images are provided in Chapter 11 (p. 227).


Obstentrics_Williams

Obstentrics_Williams. Evaluation of the relationship between the placenta and the internal cervical os is an essential component of the standard sonogram. Abnormalities of the placenta and umbilical cord are reviewed in Chapter 6 (p. 111). Although the cervix may be imaged transabdominally (Fig. 10-4), this is often limited FIGURE 10-4 A. Transabdominal image of the cervix depicting the internal os and external as. B. Transvaginal imaging a more accurate evaluation of the cervix and should be used for medical decision-making. In this image, arrowheads mark the endocervical canal. (Used with permission from Dr. Emily Adhikari.) TABLE 10-8. Criteria for Transvaginal Evaluation of the Cervix Imaging the Cervix Maternal bladder should be empty. Transducer is inserted under real-time observation, identiying midsagittal intenal os, and then extenal os, while keeping the internal os in view.


Obstentrics_Williams

Obstentrics_Williams. Maternal bladder should be empty. Transducer is inserted under real-time observation, identiying midsagittal intenal os, and then extenal os, while keeping the internal os in view. Internal os, external os, and entire endocervical canal should be visible. The internal os may appear as a small triangular indentation at the junction of the amnionic cavity and endocervical canal. Image is enlarged so that the cervix fills approximately 75% of the screen. Anterior and posterior width of the cervix should be approximately equal. Transducer is pulled back slightly until the image begins to blur, ensuring that pressure is not placed on the cervix, then inserted only enough to restore a clear image. and without fundal or suprapubic pressure, to assess for dynamic change-or shortening on real-time imaging. Measuring the Cervix Calipers are placed where anterior and posterior walls of cervix meet. Endocervical canal appears as a faint, linear echodensity.


Obstentrics_Williams

Obstentrics_Williams. Measuring the Cervix Calipers are placed where anterior and posterior walls of cervix meet. Endocervical canal appears as a faint, linear echodensity. If canal has a curved contour, a straight line between the internal and external os will deviate from the path of the endocervical canal. If midpoint of the line between the internal and external canal deviates by �3 mm from the endocervical canal, measure the cervical length in two linear segments. Funneling, sludge (debris), or dynamic change is noted. At least three separate images are measured during a period of at least 3 minutes to allow for dynamic change. Visualization of cervical shortening on real-time imaging, with or without fundal or suprapubic pressure, raises preterm birth risks. Shortest cervical length image that meets all criteria should be used. Modified from lams, 2013.


Obstentrics_Williams

Obstentrics_Williams. Shortest cervical length image that meets all criteria should be used. Modified from lams, 2013. by technical factors that include maternal habitus, cervical position, or shadowing by the fetal presenting part. In addition, the maternal bladder or pressure from the transducer may artificially elongate the appearance of the cervix. As a result, values from transabdominal or transvaginal measurement of the cervix can difer significantly.


Obstentrics_Williams

Obstentrics_Williams. If the cervix appears shortened or if it cannot be adequately visualized during transabdominal evaluation, transvaginal assessment is considered (American Institute of Ultrasound in Medicine, 2013b). Only cervical length measurements obtained transvaginally at or beyond 16 weeks' gestation are considered sufficiently accurate for clinical decision-making (see Fig. 10-4). A foreshortened cervix is associated with an elevated risk for preterm birth, particularly in the setting of prior preterm birth, and the degree of risk rises proportionally with the degree of cervical shortening (Chap. 42, p. 815).


Obstentrics_Williams

Obstentrics_Williams. To measure the cervix transvaginally, the imaging criteria shown in Table 10-8 are followed. he endocervical canal should be visible in its entirety, and images ideally are obtained over several minutes to allow for dynamic change. During examination, visible funneling or debris is sought. Funneling is a protrusion of amnionic membranes into a portion of the endocervical canal that has dilated (Fig. 10-5). Funneling is not an independent predictor of preterm birth, however, it is associated with cervical shortening, and transvaginal assessment is recommended if a funnel is suspected transabdominally. The cervical length is measured distal to the funnel, because the base of the funnel becomes the functional internal os. If the cervix is dilated, as with cervical insuiciency, the membranes may prolapse through the endocervical canal and into the vagina, producing an


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-5 Transvaginal image depicting a foreshortened cervix with funneling. Funneling is a protrusion of amnionic membranes into a portion of the endocervical canal that has dilated. The distal protruding edge of the funnel becomes the functional internal os (left arrow). Thus, the measured cervical length, which lies between the arrows, should not include the funnel. (Used with permission from Dr. Emily Adhikari.) FIGURE 10-7 Transcerebellar view of the posterior fossa, demonstrating measurement of the cerebellum (+), cisterna magna (x), and nuchal fold thickness (backet). Care is taken not to angle obliquely down the spine, which may artificially increase the nuchal fold measurement.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-6 The transventricular view depicts the lateral ventricles, which contain the echogenic choroid plexus (CP). The lateral ventricle is measured at the atrium (arrows), which is the confluence of the temporal and occipital horns. A normal measurement is between 5 and 10 mm throughout the second and third trimesters. The atria measured 6 mm in this 21-week fetus. hourglass appearance. Sludge or debris represents an aggregate of particulate matter within the amnionic sac, close to the internal os. In pregnancies at risk for preterm birth, sludge is associated with a further increased risk.


Obstentrics_Williams

Obstentrics_Williams. Many fetal anomalies and syndromes may be characterized with targeted sonography, and selected abnormalities are discussed subsequently. This list is not intended to be comprehensive but covers abnormalities commonly detected with standard sonography and those that are potentially amenable to fetal therapy. Sonographic features of chromosomal abnormalities are reviewed in Chapters 13 and 14, and fetal therapy is discussed in Chapter 16.


Obstentrics_Williams

Obstentrics_Williams. Standard sonographic evaluation of the fetal brain includes three transverse (axial) views. The transthalamic view is used to measure the BPD and HC and includes the midline falx, cavum septum pellucidum (CSP), and thalami (see Fig. 10-IA). The CSP is the space between the two laminae that separate the frontal horns of the lateral ventricles. Inability to visualize a normal CSP may indicate a midline brain abnormality such as agenesis of the corpus callosum, lobar holoprosencephaly, or septo-optic dysplasia (de Morsier syndrome). The transventricular view includes the lateral ventricles, which contain the echogenic choroid plexus (Fig. 10-6). The ventricles are measured at their atrium, which is the confluence of the temporal and occipital horns. The transcerebellar view is obtained by angling the transducer back through the posterior fossa (Fig. 10-7). In this view, the cerebellum and cisterna magna are measured, and between 15 and about 20 weeks, the nuchal skinfold thickness may


Obstentrics_Williams

Obstentrics_Williams. angling the transducer back through the posterior fossa (Fig. 10-7). In this view, the cerebellum and cisterna magna are measured, and between 15 and about 20 weeks, the nuchal skinfold thickness may also be measured. From 15 until 22 weeks' gestation, the cerebellar diameter in millimeters is roughly equivalent to the gestational age in weeks (Goldstein, 1987). The cisterna magna normally measures between 2 and 10 mm. Efacement of the cisterna magna is present in the Chiari II maormation, discussed later (p. 193).


Obstentrics_Williams

Obstentrics_Williams. Imaging of the spine includes evaluation of the cervical, thoracic, lumbar, and sacral regions (Fig. 10-8). Representative spinal images for record keeping are often obtained in the sagittal or coronal plane, but real-time imaging of each spinal segment in the transverse plane is more sensitive for anomaly detection. Transverse images demonstrate three ossification centers. The anterior ossiication center is the vertebral body, and the posterior paired ossification centers represent the FIGURE 10-8 Normal fetal spine. In this sagittal image of a 21-week fetus, the cervical (, thoracic (, lumbar (, and sacral spine (5) are depicted. Arrows denote the parallel rows of paired posterior ossification centers-representing the junction of vertebralolamina and pedicles.


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Obstentrics_Williams. FIGURE 10-9 Anencephaly/acrania. A. Acrania. This ll-week fetus has absence of the cranium, with protrusion of a disorganized mass of brain tissue that resembles a "shower cap" (arrows) and a characteristic triangular facial appearance. B. Anencephaly. This sagittal image shows the absence of forebrain and cranium above the skull base and orbit. The long white arrow points to the fetal orbit, and the short white arrow indicates the nose. junction of vertebral laminae and pedicles. Ossiication of the spine proceeds in a cranial-caudal fashion, such that ossification of the upper sacrum (51-52) is not generally visible sonographically before 16 weeks' gestation, and ossification of the entire sacrum may not be visible until 21 weeks (De Biasio, 2003). Thus, detection of some spinal abnormalities can be challenging in the early second trimester.


Obstentrics_Williams

Obstentrics_Williams. If a brain or spinal abnormality is identified, targeted sonography is indicated. he International Society of Ultrasound in Obstetrics and Gynecology (2007) has published guidelines for a "fetal neurosonogram." Fetal MR imaging may also be helpful (p. 217). hese defects include anencephaly, myelomeningocele (also called spina bifida), cephalocele, and other rare spinal fusion (or schisis) abnormalities. hey result from incomplete closure of the neural tube by the embryonic age of 26 to 28 days. heir birth prevalence is 0.9 in 1000 in the United States and most of Europe and 1.3 in 1000 in the United Kingdom (Cragan, 2009; Dolk, 2010). Many neural-tube defects can be prevented with folic acid supplementation. When isolated, neural-tube defect inheritance is multifactorial, and the recurrence risk without periconceptional folic acid supplementation is 3 to 5 percent (Chap. 13, p. 270).


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Obstentrics_Williams. Screening for neural-tube defects with maternal serum alpha-fetoprotein (MSAFP) has been ofered routinely as part of prenatal care since the 1980s (Chap. 14, p. 283). Women currently have the option of neural-tube defect screening with MSAFP, sonography, or both (American College of Obstetricians and Gynecologists, 2016). Serum screening is generally performed between 15 and 20 weeks' gestation. And, if using an upper threshold of 2.5 multiples of the median (MoM), the anticipated detection rate is at least 90 percent for fetal anencephaly and 80 percent for myelomeningocele. Targeted sonography is the preferred diagnostic test, and in addition to characterizing the neural-tube defect, it may identiy other abnormalities or conditions that also result in MSAFP elevation (Table 14-6, p. 283).


Obstentrics_Williams

Obstentrics_Williams. Anencephay is characterized by absence of the cranium and telencephalic structures above the level of the skull base and orbits (Fig. 10-9). Acrania is absence of the cranium with protrusion of disorganized brain tissue. Both are uniformly lethal and are generally considered together, with anencephaly as the final stage of acrania (Bronshtein, 1991). These anomalies are often diagnosed in the late first trimester, and with adequate visualization, virtually all cases may be diagnosed in the second trimester. Inability to image the BPD raises suspicion. The face often appears triangular, and sagittal images readily demonstrate absence of the ossified cranium. Hydramnios from impaired fetal swallowing is common in the third trimester. Cphaocee is the herniation of meninges through a cranial defect, tpically located in the midline occipital region (Fig. 10-10).


Obstentrics_Williams

Obstentrics_Williams. Cphaocee is the herniation of meninges through a cranial defect, tpically located in the midline occipital region (Fig. 10-10). FIGURE 10-10 Encephalocele. This transverse image depicts a large defect in the occipital region of the cranium (arrows) through which meninges and brain tissue have herniated. FIGURE 10-1 1 Myelomeningocele, In this sagittal image of a lumbosacral myelomeningocele, the arrowheads indicate nerve roots within the anechoic herniated sac. The overlying skin is visible above the level of the spinal defect but abruptly stops at the defect (arrow),


Obstentrics_Williams

Obstentrics_Williams. When brain tissue herniates through the skull defect, the anomaly is termed an encephaocee. Herniation of the cerebellum and other posterior fossa structures constitutes a Chiari II maomaion. Associated hydrocephalus and microcephaly are common, and survivors have a high incidence of neurological deficits and intellectual disability. Cephalocele is an important feature of the autosomal recessive Meckel-Guber syndrome, which includes cystic renal dysplasia and polydactyly. A cephalocele not located in the occipital midline rises suspicion for amnionic-band sequence (Chap. 6, p. 116).


Obstentrics_Williams

Obstentrics_Williams. Spina bia is a defect in the vertebrae, typically the dorsal arches, with exposure of the meninges and spinal cord. The birth prevalence approximates 1 in 2000 (Cragan, 2009; Dolk, 2010). Most cases are open spina bia-the defect includes the skin and sot tissues. Herniation of a meningeal sac containing neural elements is termed a myelomeningocele (Fig. 10-1i1). When only a meningeal sac is present, the defect is a meningocele. Although the sac may be easier to image in the sagittal plane, transverse images more readily demonstrate separation or splaying of the laterl processes.


Obstentrics_Williams

Obstentrics_Williams. Detection of spina bifida is aided by two characteristic cranial findings (Nicolaides, 1986). Scalloping of the frontal bones is termed the lemon sign, and anterior curvature of the cerebellum with efacement of the cisterna magna is the banana sign (Fig. 10-12). These indings are manifestations of the Chiari II malformation, also called the Arnold-Chiari maormation. This develops when downward displacement of the spinal cord pulls a portion of the cerebellum through the foramen magnum and into the upper cervical canal. Ventriculomegay is another frequent associated sonographic finding, particularly after midgestation. More than 80 percent of infants with open spina bifida require ventriculoperitoneal shunt placement. A small BPD is often present as well. Children with spina biida require multidisciplinary care to address problems related to the defect, therapeutic shunting, and deicits in swallowing, bladder and bowel function, and ambulation. Fetal myelomeningocele surgery is


Obstentrics_Williams

Obstentrics_Williams. multidisciplinary care to address problems related to the defect, therapeutic shunting, and deicits in swallowing, bladder and bowel function, and ambulation. Fetal myelomeningocele surgery is discussed


Obstentrics_Williams

Obstentrics_Williams. Chapter 16 (p. 319). Characterized by distention of the cerebral ventricles by cerebrospinal luid (CSF), this finding is a nonspecific marker of abnormal brain development (Pilu, 2011). The atrium normally measures between 5 and 10 mm from 15 weeks' gestation until term (see Fig. 10-6). Mild ventriculomegaly is diagnosed when the atrial width measures 10 to 15 mm (Fig. 10-13), and overt or severe ventriculomegaly when it exceeds 15 mm. The larger the atrium, the greater the likelihood of an abnormal outcome (Gaglioti, 2009; J06, 2008). CSF is produced within the ventricles by the choroid plexus, which is composed of loose connective tissue surrounding an epithelium-lined capillary core. he choroid plexus often appears to dangle within the ventricle when severe ventriculomegaly is present.


Obstentrics_Williams

Obstentrics_Williams. Ventriculomegaly may be caused by various genetic and environmental insults. It may be due to other central nervous system (CNS) abnormalities-such as Dandy-Walker malformation or holoprosencephaly, to an obstructive process-such as aqueductal stenosis, or to a destructive process-such as porencephaly or an intracranial teratoma. Initial evaluation includes a targeted examination of fetal anatomy, testing for congenital infections such as cytomegalovirus and toxoplasmosis, and chromosomal microarray analysis, which is described in Chapter 13 (p. 271). Fetal MR imaging should be considered to assess for associated abnormalities that may not be detectable sonographically.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-12 Cranial findings in myelomeningocele, A. Image of a fetal head at the level of the lateral ventricles demonstrates inward bowing or scalloping of the frontal bones (arrows)-the lemon sign. B. Image of a fetal head at the level of the posterior fossa shows anterior curvature of the cerebellum (arrows) with effacement of the cisterna magna-the banana sign. FIGURE 10-13 Ventriculomegaly. In this transverse view of the cranium, the white line depicts measurement of the atrium of the lateral ventricle, which measured 12 mm, consistent with mild ventriculomegaly.


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Obstentrics_Williams. Prognosis is generally determined by etiology, severity, and rate of progression. However, even with mild-appearing and isolated ventriculomegaly, prognosis can vary widely. In a systematic review of nearly 1500 mild-to-moderate cases, 1 to 2 percent were associated with congenital infection, 5 percent with aneuploidy, and 12 percent with neurological abnormality (Devaseelan, 2010). A neurological abnormality was significantly more common if ventriculomegly progressed with advancing gestation. Agenesis of the Corpus Callosum


Obstentrics_Williams

Obstentrics_Williams. Agenesis of the Corpus Callosum The corpus callosum is the major iber bundle connecting reciprocal regions of the cerebral hemispheres. With complete agenesis of the corpus callosum, a normal cavum septum pellucidum cannot be visualized sonographically. Also, the frontal horns are displaced laterally, and the atria show mild enlargement posteriorly-such that the ventricle has a characteristic "teardrop" appearance (Fig. 10-14). Callosal dysgenesis involves only the caudal portions-the body and splenium-and consequently may be more diicult to detect prenatally.


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Obstentrics_Williams. In population-based studies, agenesis of the corpus callosum has a prevalence of 1 in 5000 births (Glass, 2008; Szabo, 2011). In a review of apparently isolated cases, fetal MR imaging identiied additional brain abnormalities in more than 20 percent (Sotiriadis, 2012). If the anomaly was still considered isolated following MR imaging, normal developmental outcome was reported in 75 percent of cases, but severe disability occurred in 12 percent. Agenesis of the corpus callosum is associated with other anomalies, aneuploidy, and more than 200 genetic syndromes. Thus, genetic counseling can be challenging. FIGURE 10-14 Agenesis of the corpus callosum. This image demonstrates a "teardrop" shaped ventricle with mild ventriculomegaly (dotted line) and laterally displaced frontal horns (arrow). A normal cavum septum pellucidum cannot be visualized.


Obstentrics_Williams

Obstentrics_Williams. In early normal brain development, the prosencephalon or forebrain divides as it becomes the telencephalon and diencephalon. With holoprosencephaly, the prosencephalon fails to divide completely into two separate cerebral hemispheres and underlying paired diencephalic structures. Main forms of holoprosencephaly are a continuum that contains, with decreasing severity, alobar, semilobar, and lobar types. In the most severe form-alobar holoprosencephay-a single monoventricle, with or without a covering mantle of cortex, surrounds fused central thalami (Fig. 10-15). In semilobar holoprosencephay, partial separation of the hemispheres occurs. Lobar holoprosencephay is characterized by a variable degree of fusion of frontal structures and should be considered when a normal CSP cannot be seen.


Obstentrics_Williams

Obstentrics_Williams. Diferentiation into two cerebral hemispheres is induced by prechordal mesenchyme, which is also responsible for diferentiation of the midline face. Thus, holoprosencephaly may be associated with anomalies of the orbits and eyeshypotelorism, cyclopia, or micro-ophthalmia; lips-median cleft; or nose-ethmocephaly, cebocephaly, or arhinia with proboscis (see Fig. 10-15). The birth prevalence of holoprosencephaly is only 1 in 10,000 to 15,000. However, the abnormality has been identiied in nearly 1 in 250 early abortuses, which attests to the extremely high in-utero lethality (Orioli, 2010; Yamada, 2004). The alobar form accounts for 40 to 75 percent of cases, and 30 to 40 percent have a numerical chromosomal abnormality, particularly trisomy 13 (Orioli, 2010; Solomon, 2010). Conversely, two thirds of trisomy 13 cases are found to have holoprosencephaly. Fetal karyotype or chromosomal microarray analysis should be ofered when this anomaly is identiied.


Obstentrics_Williams

Obstentrics_Williams. This posterior fossa abnormality is characterized by agenesis of the cerebellar vermis, posterior fossa enlargement, and elevation of the tentorium. Sonographically, luid in the enlarged FIGURE 10-15 Alobar holoprosencephaly. A. Transverse cranial image of a fetus with alobar holoprosencephaly, depicting fused thalami (Th) encircled by a monoventricle () with a covering mantle (M) of cortex. The midline falx is absent. (Reproduced with permission from Rafael Levy, ROMS.) B. In this profile view of the face, a soft tissue mass-a proboscis (arrow), protrudes from the region of the forehead.


Obstentrics_Williams

Obstentrics_Williams. cisterna magna visibly communicates with the fourth ventricle through the cerebellar vermis defect, with visible separation of the cerebellar hemispheres (Fig. 10-16). The birth prevalence approximates 1 in 12,000 (Long, 2006). Associated anomalies and aneuploidy are common. These include ventriculomegaly in 30 to 40 percent, other anomalies in approximately 50 percent, and aneuploidy in 40 percent (Ecker, 2000; Long, 2006). Dandy-Walker malformation is also associated with numerous genetic and sporadic syndromes, congenital viral infections, and teratogen exposure, all of which greatly afect the prognosis. Thus, the initial evaluation mirrors that for ventriculomegaly (p. 193).


Obstentrics_Williams

Obstentrics_Williams. Inerior vermian agenesis, also called Dandy-Walker variant, is a term used when only the inferior portion of the vermis is absent. But, even when vermian agenesis appears to be partial and relatively subtle, the prevalence of associated anomalies and aneuploidy is still high, and the prognosis is often poor (Ecker, 2000; Long, 2006). Schizencephaly is a rare brain abnormality characterized by clefts in one or both cerebral hemispheres, typically involving the perisylvian fissure. The cleft is lined by heterotopic gray matter and communicates with the ventricle, extending through the cortex to the pial surface (Fig. 10-17). Schizencephaly is believed to be an abnormality of neuronal migration, which explains its typically delayed recognition until after midpregnancy (Howe, 2012). It is associated with absence of the cavum septum pellucidum, resulting in the frontal horn communication shown in the image below.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-16 Dandy-Walker malformation. This transcerebellar image demonstrates agenesis of the cerebellar vermis. The cerebellar hemispheres (+) are widely separated by a fluid collection that connects the 4th ventricle (asterisk) to the enlarged cisterna magna (eM). FIGURE 10-17 Schizencephaly. This transverse image ofthe fetal head shows a large cleft that extends from the right lateral ventricle through the cortex. Because the borders of the cleft are sepa rate, the defect is termed open-lipped. (Used with permission from Michael Davidson, ROMS.) FIGURE 10-19 Midline face. This view demonstrates the integrity of the upper lip. FIGURE 10-18 Sacrococcygeal teratoma. Sonographically, this tumor appears as a solid and/or cystic mass that arises from the anterior sacrum and tends to extend inferiorly and externally as it grows. In this image, a 7 x 6 cm inhomogeneous solid mass is visible below the normal-appearing sacrum. There is also an internal component to the tumor.


Obstentrics_Williams

Obstentrics_Williams. In contrast, porencephaly is a cystic space within the brain that is lined by white matter and mayior may not communicate with the ventricular system. It is generally considered to be a destructive lesion and may develop following intracranial hemorrhage in the setting of neonatal alloimmune thrombocytopenia or following death of a monochorionic co-twin (Fig. 45-20, p. 878). Fetal MR imaging should be considered when either of these CNS anomalies is identiied.


Obstentrics_Williams

Obstentrics_Williams. his germ cell tumor is one of the most common tumors in neonates, with a birth prevalence of approximately 1 in 28,000 (Derikx, 2006; Swamy, 2008). It is thought to arise from the totipotent cells along Hensen node, anterior to the coccyx. Classification of sacrococcygeal teratoma (SCT) includes four types (Altman, 1974). Type 1 is predominantly external with a minimal presacral component; type 2 is predominantly external but with a significant intrapelvic component; type 3 is predominantly internal but with abdominal extension; and type 4 is entirely internal with no external component. he tumor histological type may be mature, immature, or malignant.


Obstentrics_Williams

Obstentrics_Williams. Sonographiclly, SCT appears as a solid and/or cystic mass that arises rom the anterior sacrum and usually extends inferiorly and externally as it grows (Fig. 10-18). Solid components oten have varying echogenicity, appear disorganized, and may enlarge rapidly with advancing gestation. Internal pelvic components may be more challenging to visualize, and fetal MR imaging should be considered. Hydramnios is frequent, and hydrops may develop from high-output cardiac failure, either as a consequence of tumor vascularity or secondary to bleeding within the tumor and resultant anemia. Mentioned throughout this chapter, hydrops is more ully described in Chapter 15 (p. 309). Fetuses with tumors >5 cm oten require cesarean delivery, and classical hysterotomy may be needed (Gucciardo, 2011). s shown in Figure 16-3 (p. 320), fetal surgery is suitable for some SCT cases.


Obstentrics_Williams

Obstentrics_Williams. his rare anomaly is characterized by absence of the sacral spine and often portions of the lumbar spine. It is approximately 25 times more common in diabetic pregnancies (Garne, 2012). Sonographic indings include a spine that appears abnormally short, lacks normal lumbosacral curvature, and terminates abruptly above the level of the iliac wings. Because the sacrum does not lie between the iliac wings, they are abnormally close together and may appear "shield-like." here may also be abnormal positioning of the lower extremities and lack of normal local soft tissue development. Caudal regression should be diferentiated from sirenomelia, which is a rare anomaly characterized by a single fused lower extremity that occupies the midline.


Obstentrics_Williams

Obstentrics_Williams. Normal fetal lips and nose are shown in Figure 10-19. A fetal profile is not a required component of standard examination but may be helpful in identiying cases of micrognathia-an abnormally small jaw (Fig. 10-20). Micrognathia should be considered in the evaluation of hydramnios (Chap. 11, p. 227). Use of the ex-utero intrapartum treatment (EI) procedure for severe micrognathia is discussed in Chapter 16 (p. 327). here are three main types of clefts. he irst type, clt lip and palate, always involves the lip, may also involve the hard palate, can be unilateral or bilateral, and has a birth prevalence that approximates 1 in 1000 (Cragan, 2009; Dolk, 2010). If isolated, the inheritance is multifactorial-with a recurrence risk of 3 to 5 percent for one prior afected child. If a cleft is visible in the upper lip, a transverse image at the level of the alveolar ridge may demonstrate that the defect also involves the primary palate (Fig. 10-21).


Obstentrics_Williams

Obstentrics_Williams. In one systematic review of low-risk pregnancies, cleft lip was identiied so no graphically in only about half of cases FIGURE 10-20 Fetal profile. A. This image depicts a normal fetal profile. B. This fetus has severe micrognathia, which creates a severely recessed chin. (Maarse, 2010). Approximately 40 percent of those detected in prenatal series are associated with other anomalies or syndromes, and aneuploidy is common (Maarse, 2011; Oferdal, 2008). The rate of associated anomalies is highest for bilateral defects that involve the palate. Using data from the Utah Birth Defect Network, Walker and associates (2001) identified aneuploidy in 1 percent with cleft lip alone, 5 percent with unilateral cleft lip and palate, and 13 percent with bilateral cleft lip and palate. It is reasonable to ofer fetal chromosomal microarray analysis when a cleft is identiied.


Obstentrics_Williams

Obstentrics_Williams. he second type of cleft is isolated clt palate. I t begins at the uvula, may involve the soft palate, and occasionally involves the hard palate-but does not involve the lip. The birth prevalence approximates 1 in 2000 (Dolk, 2010). Identiication of isolated cleft palate has been described using specialized 2-and 3-dimensional sonography (Ramos, 2010; Wilhelm, 2010). However, it is not expected to be visualized during a standard sonographic examination (Maarse, 2011; Oferdal, 2008). A third type of cleft is median clt lp, which is found in association with several conditions. hese include agenesis of the primary palate, hypotelorism, and holoprosencephaly. FIGURE 10-21 Cleft lip/palate. A. This fetus has a prominent unilateral (left-sided) cleft lip. B. Transverse view of the palate in the same fetus demonstrates a defect in the alveolar ridge (arrow), The tongue ) is also visible.


Obstentrics_Williams

Obstentrics_Williams. Median clefts may also be associated with hypertelorism and frontonasal hyperplasia, formerly called the median clt ace syndrome. This venolymphatic malformation is characterized by luidilled sacs that extend from the posterior neck (Fig. 10-22). Cystic hygromas may be diagnosed as early as the irst trimester and vary widely in size. They are believed to develop when lymph from the head fails to drain into the jugular vein and accumulates instead in jugular lymphatic sacs. Their birth prevalence approximates 1 in 5000. But, reflecting the high in-utero lethality of the condition, the first-trimester incidence exceeds 1 in 300 (Malone, 2005).


Obstentrics_Williams

Obstentrics_Williams. Up to 70 percent of cystic hygromas are associated with aneuploidy. When cystic hygromas are diagnosed in the irst trimester, trisomy 21 is the most common aneuploidy, followed by 45,X and trisomy 18 (Kharrat, 2006; Malone, 2005). Firsttrimester fetuses with cystic hygromas are ive times more likely to be aneuploid than fetuses with a thickened nuchal translucency. When cystic hygromas are diagnosed in the second trimester, approximately 75 percent of aneuploid cases are 45,X-Turner syndrome Gohnson, 1993; Shulman, 1992).


Obstentrics_Williams

Obstentrics_Williams. Even in the absence of aneuploidy, cystic hygromas confer a significantly greater risk for other anomalies, particularly cardiac anomalies that are flow-related. These include hypoplastic let heart and coarctation of the aorta. Cystic hygromas also may be part of a genetic syndrome. One is Noonan yndrome, an autosomal dominant disorder that shares several features with Turner syndrome, including short stature, lymphedema, high-arched palate, and oten pulmonary valve stenosis. Large cystic hygromas are usually associated with hydrops fetalis, rarely resolve, FIGURE 10-22 Cystic hygromas. A. This 9-week fetus with a cystic hygroma (arrow) was later found to have Noonan syndrome. B. Massive multiseptated hygromas (arrowheads) in the setting of hydrops fetalis at 15 weeks' gestation.


Obstentrics_Williams

Obstentrics_Williams. and carry a poor prognosis. Small hygromas may undergo spontaneous resolution, and provided that fetal karyotype and echocardiography results are normal, the prognosis may be good. The likelihood of a nonanomalous liveborn neonate with normal karyotype following identiication of first-trimester hygroma is approximately 1 in 6 (Kharrat, 2006; Malone, 2005).


Obstentrics_Williams

Obstentrics_Williams. he lungs appear homogeneous and surround the heart. In the four-chamber view of the heart, they comprise approximately two thirds of the area, with the heart occupying the remaining third. The thoracic circumference is measured at the skin line in a transverse plane at the level of the four-chamber view. In cases of suspected pulmonary hypoplasia secondary to a small thorax, such as with severe skeletal dysplasia, comparison with a reference table may be helpul (Appendix, p. 1266). Various abnormalities may appear so no graphically as cystic or solid space-occupying lesions or as an efusion outlining the heart or lung(s). Fetal therapy for thoracic abnormalities is discussed in Chapter 16 (p. 324).


Obstentrics_Williams

Obstentrics_Williams. This is a defect in the diaphragm through which abdominal organs herniate into the thorax. It is let-sided in approximately 75 percent of cases, right-sided in 20 percent, and bilateral in 5 percent (Gallot, 2007). he prevalence of congenital diaphragmatic hernia (CDH) is 1 in 3000 to 4000 births (Cragan, 2009; Dolk, 2010). Associated anomalies and aneuploidy are found in 40 percent of cases (Gallot, 2007; Stege, 2003). With suspected CDH, targeted sonography and fetal echo cardiography should be performed, and fetal chromosomal microarray analysis should be ofered. In population-based series, the presence of an associated abnormality reduces the overall survival rate of neonates with CDH from approximately 50 percent to about 20 percent (Colvin, 2005; Gallot, 2007). If there are no associated abnormalities, the major causes of neonatal mortality are pulmonary hypoplasia and pulmonary hypertension.


Obstentrics_Williams

Obstentrics_Williams. Sonographically, left-sided CDH typically shows dextroposition of the heart toward the right side of the thorax and a cardiac axis pointing toward the midline (Fig. 10-23). Associated findings include the stomach bubble or bowel peristalsis in the chest and a wedge-shaped mass-the liver-located anteriorly in the left hemithorax. Liver herniation complicates at least 50 percent of cases and is associated with a 30-percent reduction in the survival rate (Mullassery, 2010). With large lesions, impaired swallowing and mediastinal shift may result in hydramnios and hydrops, respectively. Eforts to reduce neonatal mortality rates and need for extracorporeal membrane oxygenation (ECMO) have focused on indicators such as the sonographic lung-to-head ratio, MR imaging measurements of lung volume, and the degree of liver herniation Gani, 2012; Oluyomi-Obi, 2016; Worley, 2009). These and fetal therapy for CDH are reviewed in Chapter 16 (p. 323).


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-23 Congenital diaphragmatic hernia. In this transverse view of the thorax, the heart is shifted to the far right side of the chest by a let-sided diaphragmatic hernia containing stomach (5), liver (, and bowel (B). This abnormality represents a hamartomatous overgrowth of terminal bronchioles that communicates with the tracheobronchial tree. It is also called congenital pulmonay airway maormation (CPM), based on an understanding that not all histopathological types are cystic or adenomatoid (Azizkhan, 2008; Stocker, 1977, 2002). The estimated prevalence is 1 in 6000 to 8000 births, and this rate is rising because of improved sonographic detection of milder cases (Burge, 2010; Duncombe, 2002).


Obstentrics_Williams

Obstentrics_Williams. Sonographically, congenital cystic adenomatoid malformation (CCAM) is a well-circumscribed thoracic mass that may appear solid and echogenic or may have one or multiple variably sized cysts (Fig. 10-24). It usually involves one lobe, has blood supply from the pulmonary artery, and drains into the pulmonary veins. Lesions with cysts :5 mm are generally FIGURE 10-24 Transverse (A) and sagittal (8) images of a 26-week fetus with a very large left-sided microcystic congenital cystic adenomatoid malformation (CCAM). The mass () fills the thorax and has shifted the heart to the far right side of the chest, with development of ascites (asterisks). Fortunately, the mass did not continue to grow, the ascites resolved, and the neonate was delivered at term and did well following resection. termed macrocystic, and lesions with cysts <5 mm are termed microcystic (Adzick, 1985).


Obstentrics_Williams

Obstentrics_Williams. termed macrocystic, and lesions with cysts <5 mm are termed microcystic (Adzick, 1985). In a review of 645 CCM cases, the overall survival rate exceeded 95 percent, and 30 percent of cases demonstrated apparent prenatal resolution. The other 5 percent of cases typically very large lesions with associated mediastinal shift were complicated by hydrops, and the prognosis was poor (Cavoretto, 2008). CCAMs often become less conspicuous with advancing gestation. However, a subset of CCAMs dem onstrates rapid growth between 18 and 26 weeks' gestation. lesions to forestall growth and potentially ameliorate hydrops (Curran, 2010; Peranteau, 2016). If a large dominant cyst is present, thoracoamnionic shunt placement may lead to hydrops resolution. Fetal therapy for CCAM is discussed in Chapter 16 (p.i324). Also called a bronchopulmonary sequestration, this abnormal ity is an accessory lung bud "sequestered" from the tracheo bronchial tree, that is, a mass of nonfunctioning lung tissue.


Obstentrics_Williams

Obstentrics_Williams. Also called a bronchopulmonary sequestration, this abnormal ity is an accessory lung bud "sequestered" from the tracheo bronchial tree, that is, a mass of nonfunctioning lung tissue. Most cases diagnosed prenatally are extralobar, which means they are enveloped in their own pleura. Overall, however, most sequestrations present in adulthood and are intralobar-within the pleura of another lobe. Extralobar pulmonary sequestra tion is considered significantly less common than CCAM, and no precise prevalence has been reported. Lesions have a left sided predominance and most often involve the left lower lobe. Of cases, 10 to 20 percent are located below the diaphragm, 10 percent of cases (Yildirim, 2008).


Obstentrics_Williams

Obstentrics_Williams. Of cases, 10 to 20 percent are located below the diaphragm, 10 percent of cases (Yildirim, 2008). Sonographically, pulmonary sequestration presents as a homogeneous, echogenic thoracic mass (Fig. 10-25A). Thus, it may resemble a microcystic CCAM. However, the blood supply is from the systemic circulation-from the aorta rather than the pulmonary artery (see Fig. 10-25B). In 5 to 10 percent with pulmonary sequestration, a large ipsilateral pleural efusion develops, and without treatment, this may result in pulmonary hypoplasia or hydrops (see Fig. 1 0-25C,D). Therapeutic thoracoamnionic shunting of efusions is discussed in Chapter 16 (p. 324). Hydrops may also result from mediastinal shift or high-output cardiac failure due to the left-toright shunt imposed by the mass. In the absence of a pleural efusion, the reported survival rate exceeds 95 percent, and 40 percent of cases demonstrate apparent prenatal resolution (Cavoretto, 2008).


Obstentrics_Williams

Obstentrics_Williams. This rare anomaly usually results from laryngeal or tracheal atresia. The normal egress of lung fluid is obstructed, and the tracheobronchial tree and lungs become massively distended. Sonographically, the lungs appear brightly echogenic, the bronchi are dilated, the diaphragm is flattened or everted, and the heart is compressed (Fig. 10-26). Venous return is impaired and ascites develops, typically followed by hydrops. In one review of 118 cases, associated anomalies were identiied in more than 50 percent (Sanford, 2012). Congenital high airway obstruction sequence (CHAOS) is a feature of the autosomal recessive Fraser syndrome and has been associated with the 22q 11.2 deletion syndrome. In some cases, the obstructed airway spontaneously perforates, which potentially confers a better prognosis. he EIT procedure has significantly improved outcome in selected cases (Chap. 16, p. 327).


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-25 Pulmonary sequestration. A. This transverse image at the level of the 4-chamber view of the heart depicts a pulmonary sequestration involving the left lower lobe in a 25-week fetus. Mass effect leads to dextroposition of the heart to the right side of the chest. B. A sagittal image shows the pulmonary sequestration supplied by a branch of the abdominal aorta. C. Over the next 3 weeks, a large ipsilateral pleural effusion develops (asterisk), resulting in mediastinal shift and dextroposition of the heart to the far right thorax. D. Following placement of a double-pigtail shunt through the chest wall and into the effusion, the effusion drained and the lung significantly reexpanded. Arrows points to coils of the pigtail shunt. (Used with permission from Dr. Elaine Duryea.)


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-26 Congenital high airway obstruction sequence (CHAOS). The lungs appear brightly echogenic, and one is marked by an "L." The bronchi, one of which is noted by an arrow, are dilated with fluid. Flattening and eversion of the diaphragm is common, as is ascites (asterisks).


Obstentrics_Williams

Obstentrics_Williams. Cardiac malformations are the most common class of congenital anomalies, and their overall prevalence is 8 in 1000 births (Cragan, 2009). Almost 90 percent of cardiac defects are multifactorial or polygenic in origin, another 1 to 2 percent result from a single-gene disorder or gene-deletion syndrome, and 1 to 2 percent stem from exposure to a teratogen such as isotretinoin, hydantoin, or maternal diabetes. Based on data from population-based registries, approximately 1 in 8 liveborn and stillborn neonates with a congenital heart defect has a chromosomal abnormality (Dolk, 2010; Hartman, 201l). Of chromosomal abnormalities associated with cardiac anomalies, trisomy 21 accounts for more than 50 percent of cases. Others are trisomy 18, 22q 11.2 deletion, trisomy 13, and monosomy X (Hartman, 2011). Of these aneuploid fetuses, 50 to 70 percent also have extracardiac anomalies. Chromo defects are found.


Obstentrics_Williams

Obstentrics_Williams. Traditionally, detection of congenital cardiac anomalies is more challenging than for anomalies of other organ systems. 40 percent of those with major cardiac anomalies before 22 weeks' gestation, and specialized sonography may identiy 80 percent (Romosan, 2009; Trivedi, 2012). For selected anoma lies, prenatal detection may improve neonatal survival. his requiring prostaglandin infusion after birth to keep the duc tus arteriosus open (Franklin, 2002; Mahle, 2001; Tworetzky, 2001). Standard cardiac assessment includes a four-chamber view, evaluation of rate and rhythm, and evaluation of the left and right ventricular outlow tracts (Figs. 10-27 and 10-28A-C). Examination of the cardiac outflow tracts aids detection of abnormalities that might not be appreciated in the four-cham ber view. hese include tetralogy of Fallot, transposition of the great vessels, and truncus arteriosus.


Obstentrics_Williams

Obstentrics_Williams. heour-chamber view is a transverse image of the fetal tho rax at a level immediately above the diaphragm. It allows evalu ation of cardiac size, position in the thorax, cardiac axis, atria and ventricles, foramen ovale, atrial septum primum, interven tricular septum, and atrioventricular valves (see Fig. 10-27). he atria and ventricles should be similar in size, and the apex of the heart should form a 45-degree angle with the left anterior chest wall. Abnormalities of cardiac axis are frequently encoun tered with structural cardiac anomalies and occur in more than a third (Shipp, 1995).


Obstentrics_Williams

Obstentrics_Williams. The lt ventricular oulow tract view is a transverse image just above the diaphragm and demonstrates that the ascending aorta arises entirely from the left ventricle. The inteventricular septum is shown to be in continuity with the anterior wall of the aorta, and the mitral valve in continuity with the posterior wall of the aorta (see Fig. 10-28B). Ventricular septal defects and outflow tract abnormalities are often visible in this view (Fig. 10-29).


Obstentrics_Williams

Obstentrics_Williams. The right ventricular oulow tract view shows the right ventricle giving rise to the pulmonary artery (see Fig. 10-28C). Together, the left and right outflow tract views demonstrate the normal perpendicular orientation of the aorta and pulmonary artery, and the comparable size of these great arteries. Structures visible in the right ventricular outlow tract view include the right ventricle and the main pulmonary artery, which subsequently branches into the right and left pulmonary arteries. hese structures are also visible in the short axis view, shown in Figure 10-28E. This is a specialized examination of fetal cardiac structure and function designed to identiy and characterize abnormalities. Guidelines for its performance have been developed collaboratively by the American Institute of Ultrasound in Medicine,


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-27 The four-chamber view. A. Diagram demonstrat ing measurement of the cardiac axis from the four-chamber view of the fetal heart. B. Sonogram of the four-chamber view at 22 weeks' gestation shows the normal symmetry of the atria and ventricles, normal position of the mitral and triscuspid valves, pulmonary veins entering the left atrium, and descending aorta (Ao). L = left; LA = left atrium; LV = left ventricle; R = right; RA = right atrium; RV = right ventricle.


Obstentrics_Williams

Obstentrics_Williams. American College of Obstetricians and Gynecologists, Society for Maternal-Fetal .Medicine, American Society of Echocardiography, and American College of Radiology. Echocardiography indications include suspected fetal cardiac anomaly, extracardiac anomaly, or chromosomal abnormality; fetal arrhythmia; hydrops; thick nuchal translucency; monochorionic twin gestation; irst-degree relative to the fetus with a congenital cardiac defect; in vitro fertilization; maternal antiRo or anti-La antibodies; exposure to a medication associated with cardiac defects; and maternal metabolic disease associated with cardiac defects-such as pregestational diabetes or phenylketonuria (American Institute of Ultrasound in Medicine, 2013a). Components of the examination are listed in TABLE 10-9. Components of Fetal Echocardiography EvaIuation of atria Evaluation of ventricles Evaluation of great vessels Cardiac and visceral situs Atrioventricular junctions Ventriculoarterial junctions


Obstentrics_Williams

Obstentrics_Williams. EvaIuation of atria Evaluation of ventricles Evaluation of great vessels Cardiac and visceral situs Atrioventricular junctions Ventriculoarterial junctions Scanning planes, gray scale Right ventricular outflow tract Three-vessel and trachea view Short-axis view, low (ventricles) Short-axis view, high (outflow tracts) Aortic arch aPulsed-wave Doppler sonography should be used as an adjunct to evaluate these structures. Cardiac biometry and functional assessment are optional but should be considered for suspected structural/ functional abnormalities. Adapted from the American Institute of Ultrasound in Medicine,l201l3b.


Obstentrics_Williams

Obstentrics_Williams. Adapted from the American Institute of Ultrasound in Medicine,l201l3b. FIGURE 10-30 Endocardial cushion defect. A. During ventricular systole, the lateral leaflets of the mitral and triscuspid valves come together in the midline. But the atrioventricular valve plane is abnormal, a common atrium (A) is observed, and there is a visible defect (arrow) in the interventricular septum. B. During diastolic filling, opening of the atrioventricular valves more clearly demonstrates the absence of their medial leaflets. Table 10-9, and examples of nine required gray-scale imaging views are shown in Figure 10-28. Examples of selected cardiac anomalies are reviewed below.


Obstentrics_Williams

Obstentrics_Williams. Ventricular Septal Defect. This is the most common congenital cardiac anomaly and is found in approximately 1 in 300 births (Cragan, 2009; Dolk, 2010). Even with adequate visualization, the prenatal detection rate of ventricular septal defect (VSD) is low. A defect may be appreciated in the membranous or muscular portion of the interventricular septum in the four-chamber view, and color Doppler demonstrates flow through the defect. Imaging of the left ventricular outflow tract may show discontinuity of the interventricular septum as it becomes the wall of the aorta (see Fig. 10-29). Fetal VSD is associated with other abnormalities and aneuploidy, and chromosomal microarray analysis should be ofered. hat said, the prognosis for an isolated defect is good. More than a third of prenatally diagnosed VSDs close in utero, and another third close in the irst year of life (Axt-Fliedner, 2006; Paladini, 2002).


Obstentrics_Williams

Obstentrics_Williams. Endocardial Cushion Defect. This is also called an atrioventricular (A ) septal dect or A V canal dect. It has a prevalence of approximately 1 in 2500 births and is associated with trisomy 21 in more than half of cases (Christensen, 2013; Cragan, 2009; Dolk, 2010). The endocardial cushions are the crux of the heart, and defects jointly involve the atrial septum primum, interventricular septum, and medial leaflets of the mitral and tricuspid valves (Fig. 10-30). Approximately 6 percent of cases occur with heterotaxy syndromes, that is, those in which the heart and/or abdominal organs are on the incorrect side. Endocardial cushion defects associated with heterotaxy can have comorbid conduction system abnormalities resulting in third-degree AV block, which confers a poor prognosis (Chap. 16, p. 316).


Obstentrics_Williams

Obstentrics_Williams. Hypoplastic Let Heart Syndrome. This anomaly is found in approximately 1 in 4000 births (Cragan, 2009; Dolk, 2010). Sonographically, the let side of the heart may appear "illed-in" or the let ventricle may be so small and attenuated that a ventricular chamber is diicult to appreciate (Fig. 10-31). There may be no visible let ventricular inlow or outflow, and reversal of low may be documented in the aortic arch. Although this anomaly was once considered a lethal prognosis, 70 percent of afected infants may now survive to adulthood (Feinstein, 2012). Postnatal treatment consists of a three-stage palliative repair or cardiac transplantation. Still, morbidity remains high, and developmental delays are common (Lloyd, 2017; Paladini, 2017). This is a ductal-dependent lesion for which neonatal administration of prostaglandin therapy is essential. Fetal therapy for hypoplastic left heart is discussed in Chapter 16 (p. 326).


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-28 Fetal echocardiography gray-scale imaging planes. A. Four-chamber view. B. Left ventricular outflow tract view. The white arrow illustrates the mitral valve becoming the wall of the aorta. The arrow with asterisk marks the interventricular septum becoming the opposing aortic wall. C. Right ventricular outflow tract view. D. Three vessel and trachea view. E. High short-axis view (outflow tracts). F. Low short-axis view (ventricles). G. Aortic arch view. H. Ductal arch view. I. Superior and inferior vena cavae views. Ao = aorta; IVC = inferior vena cava; LA = left atrium; LV = left ventricle; PA = pulmonary artery; RA = right atrium; RV = right ventricle; SVC = superior vena cava. branous) portion of the interventricular septum. B.The left-ventricular outflow tract view of the same fetus demonstrates a break (arrow) in continuity between the interventricular septum and the anterior wall of the aorta.


Obstentrics_Williams

Obstentrics_Williams. B.The left-ventricular outflow tract view of the same fetus demonstrates a break (arrow) in continuity between the interventricular septum and the anterior wall of the aorta. FIGURE 10-29 Ventricular septal defect. A.oln this four-chamber view of a 22-week fetus, a defect (arrow) is noted in the superior (mem Tetralogy of Fallot. This anomaly occurs in approximately 1 in 3000 births (Cragan, 2009; Dolk, 2010; Nelson, 2016). It includes a ventricular septal defect; an overriding aorta; a pulmonary valve abnormality, typically stenosis; and right ventricular hypertrophy (Fig. 10-32). he last does not present before birth. Due to the location of the ventricular septal defect, the four-chamber view may appear normal.


Obstentrics_Williams

Obstentrics_Williams. Following postnatal repair, the 20-year survival rates exceed 95 percent (Knott-Craig, 1998). However, cases with pulmonay atresia have a more complicated course. There is also a variant in which the pulmonary valve is absent. These afected fetuses are at risk for hydrops and for tracheomalacia from compression of the trachea by an enlarged pulmonary artery. Cardiac Rhabdomyoma. his is the most common cardiac tumor. Approximately 50 percent of cases are associated with tuberous sclerosis, an autosomal dominant disease with multiorgan system manifestations. Tuberous sclerosis is caused by mutations in the hamartin (TSCl) and tuberin (TSC2) genes.


Obstentrics_Williams

Obstentrics_Williams. Cardiac rhabdomyomas appear as well-circumscribed echo genic masses, pler depicts flow from the right atrium to the right ventricle only, and left ventricular filling is usually within the ventricles or out not visible. C. The left ventricular outflow tract view demonstrates marked narrowing of the aorta (Ao). RV = right ventricle; LA = low tracts. They may be single or is the hypoplastic aortic root. (Used with permission from Rafael Levy, ROMS.) multiple; may grow in size during gestation; and occasionally, may lead to inlow or outflow obstruction. In cases without obstruction or large tumor size, the prognosis is relatively good from a cardiac standpoint, because the tumors tend to regress after the neonatal period. Because extracardiac findings of tuberous sclerosis may not be apparent with prenatal sonography, MR imaging may be considered to evaluate fetal CNS anatomy (p. 217).


Obstentrics_Williams

Obstentrics_Williams. Motion-mode or M-mode imaging is a linear display of cardiac cycle events, with time on the x-axis and motion on the y-axis. It is often used to measure embryonic or fetal heart rate (Fig. 10-33). If an abnormality of heart rate or rhythm is identiied, M-mode imaging permits separate evaluation of atrial and ventricular waveforms. Thus, it is particularly useful for characterizing arrhythmias and their response to treatment (Chap. 16, p. 316). M-mode can also be used to assess ventricular function and atrial and ventricular outputs. Premature Atrial Contractions. Also called atrial extrasystoles, these are the most common fetal arrhythmia and a frequent


Obstentrics_Williams

Obstentrics_Williams. Premature Atrial Contractions. Also called atrial extrasystoles, these are the most common fetal arrhythmia and a frequent FIGURE 10-31 Hypoplastic left heart syndrome. A. In this 4-chamber view at 16 weeks, the let ventricle (L) appears "filled in" and is Significantly smaller than the right ventricle (R). The tricuspid valve () is open, whereas the mitral valve appears closed (asterisk). B. Color Dop let atrium. D. The tiny circle (arrow) in this short axis view FIGURE 10-32 Tetralogy of Fallot. This image shows a ventricular septal defect with an overriding aorta in a fetus with tetralogy of Fallot. The arrow points to the aortic valve. The left ventricle (LV)and right ventricle (R) are labeled. FIGURE 10-33 M-mode, or motion mode, is a linear display of the events of the cardiac cycle, with time on the x-axis and motion on the y-axis. M-mode is used commonly to measure the fetal heart rate, as in this 12-week fetus.


Obstentrics_Williams

Obstentrics_Williams. finding. They represent cardiac conduction system immaturity and typically resolve later in gestation or in the neonatal period. Premature atrial contractions (PACs) may be conducted and thus sound like an extra beat. However, they are more commonly blocked, and with handheld Doppler they sound like a dropped beat. As shown in Figure 10-34, the dropped beat may be demonstrated with M-mode evaluation as a compensatory FIGURE 10-34 M-mode. In this image, there is normal concordance between atrial (A) and ventricular contractions (). Movement of the tricuspid valve en is also shown. There is also a premature atrial contraction (arrow) and a subsequent early ventricular contraction, followed by a compensatory pause. pause that follows the premature contraction.


Obstentrics_Williams

Obstentrics_Williams. pause that follows the premature contraction. P ACs sometimes occur with an atrial septal aneurysm but are not associated with major structural cardiac abnormalities. Older case reports describe an association with maternal cafeine consumption and with hydralazine (Lodeiro, 1989; Oei, 1989). In approximately 2 percent of cases, afected fetuses are later identified to have a supraventricular tachycardia (S) that requires urgent treatment (Copel, 2000). Accordingly, pregnancies with fetal PACs are often followed with fetal heart rate assessment as often as every 1 to 2 weeks until ectopy resolves. T reatment of fetal SVT and other arrhythmias is discussed in Chapter 16 (p. 316) . he integrity of the abdominal wall is assessed at the level of the cord insertion during the standard examination (Fig. 10-35). Ventral wall defects include gastroschisis, omphalocele, and body stalk anomaly.


Obstentrics_Williams

Obstentrics_Williams. Ventral wall defects include gastroschisis, omphalocele, and body stalk anomaly. Gastroschisis is a full-thickness abdominal wall defect located to the right of the umbilical cord insertion. Bowel herniates through the defect into the amnionic cavity (Fig. 10-36). he prevalence is approximately 1 in 2000 births Oones, 2016; Nelson, 2015). Gastroschisis is the one major anomaly more common in fetuses of younger mothers, and the average maternal age is 20 years (Santiago-Munoz, 2007). Coexisting bowel abnormalities such as jjunal atresia are found in approximately 15 percent of cases (Nelson, 2015; Overcash, 2014). Gastroschisis is not associated with aneuploidy, and the survival rate is 90 to 95 percent (Kitchanan, 2000; Nelson, 2015; Nembhard, 2001).


Obstentrics_Williams

Obstentrics_Williams. Fetal-growth restriction complicates gastroschisis in 15 to 40 percent of cases (Overcash, 2014; Santiago-Munoz, 2007). Growth restriction does not appear to be associated with adverse outcomes such as longer hospitalization or higher mortality rate (Nelson, 2015; Overcash, 2014). However, earlier gestational age at delivery does pose a risk for adverse outcome with gastroschisis, and planned delivery at 36 to 37 weeks does not confer neonatal benefit (Al-Kaf, 2016; Overcash, 2014; South, 2013).


Obstentrics_Williams

Obstentrics_Williams. Omphalocele complicates 1 in 3000 to 5000 pregnancies (Canield, 2006; Dolk, 2010). It forms when the lateral ectomesodermal folds fail to meet in the midline. This leaves the abdominal contents covered only by a two-layered sac of amnion and peritoneum into which the umbilical cord inserts (Fig. 10-37). More than half of cases are associated with other major anomalies or aneuploidy. Omphalocele also is a component of syndromes such as Beckwith-Wiedemann, cloacal exstrophy, and pentaloy of Cantrell. Smaller defects confer greater risk for aneuploidy (De Veciana, 1994). Chromosomal microarray analysis should be ofered in all cases of omphalocele. FIGURE 10-35 Normal ventral wall. Transverse view of the abdomen in a second-trimester fetus with an intact anterior abdominal wall and normal cord insertion.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-35 Normal ventral wall. Transverse view of the abdomen in a second-trimester fetus with an intact anterior abdominal wall and normal cord insertion. Body stalk anomay, also known as limb-body-wall complex or cyllosoma, is a rare, lethal anomaly characterized by abnormal formation of the body wall. Typically, no abdominal wall is visible, and the abdominal organs extrude into the extraamnionic coelom. here is close approximation or fusion of the body to the placenta, and the umbilical cord is extremely short. Acute-angle scoliosis is another feature. Amnionic bands are often identified. FIGURE 10-36 Gastroschisis. This 18-week fetus has a fullthickness ventral wall defect to the right of the cord insertion (arrowhea), through which multiple small bowel loops (B) have herniated into the amnionic cavity. FIGURE 10-37 Omphalocele. Transverse view of the abdomen showing an omphalocele as a large abdominal wall defect with exteriorized liver covered by a thin membrane.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-37 Omphalocele. Transverse view of the abdomen showing an omphalocele as a large abdominal wall defect with exteriorized liver covered by a thin membrane. he stomach is visible in nearly all fetuses after 14 weeks' gestation. If the stomach is not seen during initial evaluation, the examination is repeated, and targeted sonography should be considered. Nonvisualization of the stomach may be secondary to impaired swallowing in the setting of oligohydramnios or to underlying causes such as esophageal atresia, a craniofacial anomaly, or a CNS or musculoskeletal abnormality. Fetuses with hydrops may also have impaired swallowing.


Obstentrics_Williams

Obstentrics_Williams. he bowel, liver, gallbladder, and spleen can be identiied in many second-and third-trimester fetuses. Bowel appearance changes with fetal maturation. Occasionally, it may be bright or echogenic, which may indicate small amounts of swallowed intraamnionic blood, especially with comorbid MSAFP elevation. Bowel that appears as bright as fetal bone confers a slightly greater risk for underlying gastrointestinal malformations, for cystic ibrosis, for trisomy 21, and for congenital infection such as cytomegalovirus (Fig. 14-3, p. 287). Bowel atresia is characterized by obstruction and proximal bowel dilation. In general, the more proximal the obstruction, the more likely it is to lead to hydramnios. At times, hydramnios from proximal small-bowel obstruction can be suiciently severe to result in maternal respiratory compromise or preterm labor and may necessitate amnioreduction (Chap. 11, p. 230).


Obstentrics_Williams

Obstentrics_Williams. Esophageal atresia occurs in approximately 1 in 4000 births (Cragan, 2009; Pedersen, 2012). It may be suspected when the stomach cannot be visualized and hydramnios is present. hat said, in up to 90 percent of cases, a concomitant tracheoesophageal istula allows luid to enter the stomach, such that prenatal detection is problematic. More than half have associated anomalies or genetic syndromes. Multiple malformations are present in 30 percent of cases, and aneuploidy such as trisom) 18 or 21, in 10 percent (Pedersen, 2012). Cardiac, urinary tract, and other gastrointestinal abnormalities are the most frequently associated anomalies. Approximately 10 percent of FIGURE 10-38 Duodenal atresia. The double-bubble sign represents distension of the stomach (5) and the first part of the duodenum (0), as seen on this axial abdominal image. Demonstrating continuity between the stomach and proximal duodenum confirms that the second "bubble" is the proximal duodenum.


Obstentrics_Williams

Obstentrics_Williams. cases of esophageal atresia occur as part of the V ACTERL asso ciation, which is yertebral defects, !nal atresia, £ardiac defects, !racheo�sophageal istula, renal anomalies, and limb abnormali ties (Pedersen, 2012).


Obstentrics_Williams

Obstentrics_Williams. Duodenal atresia is found in approximately 1 in 10,000 births (Best, 2012; Dolk, 2010). It is characterized by the sonographic double-bubble sin, which represents distention of the stomach and the irst part of the duodenum (Fig. 10-38). This finding is usually not present before 22 to 24 weeks' gestation. Demonstrating continuity between the stomach and proximal duodenum confirms that the second "bubble" is the proximal duodenum. Approximately 30 percent of afected fetuses have an associated chromosomal abnormality or genetic syndrome, particularly trisomy 21. Of cases without a genetic abnormality, a third have associated anomalies, most commonly cardiac defects and other gastrointestinal abnormalities (Best, 2012). Obstructions in the more distal small bowel usually result in multiple dilated loops that may have enhanced peristaltic activity.


Obstentrics_Williams

Obstentrics_Williams. Large-bowel obstructions and anal atresia are less readily diagnosed by sonography, because hydramnios is not a typical feature and the bowel may not be signiicantly dilated. A transverse view through the pelvis may show an enlarged rectum as an anechoic structure between the bladder and the sacrum. The fetal kidneys are visible adjacent to the spine, frequently in the first trimester and routinely by 18 weeks' gestation (Fig. 10-39). he length of the kidney approximates 20 mm at 20 weeks and grows by about 1.1 mm each week thereafter (Chitty, 2003). With advancing gestation, the kidneys become relatively less echogenic, and a rim of perinephric fat aids visualization of their margins. he fetal bladder is readily visible in the second trimester as a round, anechoic structure in the anterior midline of the


Obstentrics_Williams

Obstentrics_Williams. he fetal bladder is readily visible in the second trimester as a round, anechoic structure in the anterior midline of the FIGURE 10-39 Normal fetal kidneys. The kidneys are visible adjacent to the fetal spine in this 29-week fetus. With advancing gestation, a rim of perinephric fat aids visualization of the kidney margins. A physiological amount of urine is visible in the renal pelves and is marked in one kidney by an arrow. pelvis. With application of Doppler, the bladder is outlined by the two superior vesical arteries as they become the umbilical arteries of the umbilical cord (Fig. 10-40 and Chap. 6, p. 1i17). The fetal ureters and urethra are not visible sonographically unless abnormally dilated.


Obstentrics_Williams

Obstentrics_Williams. The placenta and membranes are the major sources of amnionic fluid early in pregnancy. However, after 18 weeks' gestation, most of the luid is produced by the kidneys (Chap. 11, p. 225). Fetal urine production rises from 5 mLlhr at 20 weeks to approximately 50 mLlhr at term (Rabinowitz, 1989). Normal amnionic luid volume in the second half of pregnancy suggests urinary tract patency with at least one functioning kidney. But, unexplained oligohydramnios suggests a urinary tract defect or placental perfusion abnormality. FIGURE 10-40 Normal fetal bladder. The normal fetal bladder is readily visible as a round, fluid-filled structure in the anterior pelvis, outlined by the two superior vesical arteries as they become the umbilical arteries of the umbilical cord.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 10-41 Renal pelvis dilatation. This common finding is identified in 1 to 5 percent of pregnancies. A.oln this 34-week fetus with mild renal pelvis dilatation, the anterior-posterior diameter of the renal pelvis measured 7 mm in the transverse plane. B. Sagittal image of the kidney in a 32-week fetus with severe renal pelvis dilatation secondary to ureteropelvic junction obstruction. The arrow points to one of the rounded calyces. This finding is present in 1 to 5 percent of fetuses. It is also called urinary tract dilatation or hydronephrosis. In 40 to 90 percent of cases, it is transient or physiological and does not represent an underlying abnormality (Ismaili, 2003; Nguyen, 2010). In approximately a third of cases, a urinary tract abnormality is conirmed in the neonatal period. Of these, ureteropelvic junction (UP]) obstruction and vesicoureteral relux UR) are the most frequent.


Obstentrics_Williams

Obstentrics_Williams. he fetal renal pelvis is measured anterior to posterior in a transverse plane, and calipers are placed on the inner border of the fluid collection (Fig. 10-41). Although various thresholds have been deined, the pelvis is typically considered dilated if it exceeds 4 mm in the second trimester or 7 mm at approximately 32 weeks' gestation (Reddy, 2014). Typically, the second-trimester threshold is used to identiy pregnancies that warrant subsequent third-trimester evaluation. he Society for Fetal Urology categorized renal pelvis dilatation based on a metaanalysis of more than 100,000 screened pregnancies (Table 10-10) (Lee, 2006; Nguyen, 2010). he degree of dilatation correlates with the likelihood of an underlying abnormality. Other suggestive indings of pathology TABLE 10-10. Risk for Postnatal Urinary Abnormality According to Degree of Renal Pelvis Dilatationa Second Third Postnatal Dilatation Trimester Abnormality 4 to <7 mm 7 to <9 mm


Obstentrics_Williams

Obstentrics_Williams. TABLE 10-10. Risk for Postnatal Urinary Abnormality According to Degree of Renal Pelvis Dilatationa Second Third Postnatal Dilatation Trimester Abnormality 4 to <7 mm 7 to <9 mm Moderate 7 to �1 0 mm 9 to �15 mm 45% aSociety for Fetal Urology Classification. Modified from Lee, 2006; Nguyen, 2010. include calyceal dilatation, cortical thinning, or dilatation elsewhere along the urinary tract. Mild pyelectasis in the second trimester is associated with a slightly greater risk for Down syndrome and is considered a soft marker for this (Fig. 14-3, p.i287).