Obstentrics_Williams

Obstentrics_Williams. • Management of Second-Stage Labor With full cervical dilation, which signiies the onset of the second stage, a woman typically begins to bear down. With descent of the presenting part, she develops the urge to defecate. Uterine contractions and the accompanying expulsive forces may now last 1 minute and recur at an interval no longer than 90 seconds. As discussed earlier, the median duration of the second stage is 50 minutes in nulliparas and 20 minutes in multiparas, although the interval can vary. Monitoring intervals of the fetal heart rate were discussed on page 436, and interpretation of second-stage electronic fetal heart rate patterns is discussed in Chapter 24 (p. 469).


Obstentrics_Williams

Obstentrics_Williams. In most cases, bearing down is reflexive and spontaneous during second-stage labor. Occasionally, a woman may not employ her expulsive forces to good advantage and coaching is desirable. Her legs should be half-flexed so that she can push with them against the mattress. When the next uterine contraction begins, she is instructed to exert downward pressure as though she were straining at stool. A woman is not encouraged to push beyond the completion of each contraction. Instead, she and her fetus are allowed to rest and recover. During this period of actively bearing down, the fetal heart rate auscultated during the contraction is likely to be slow but should recover to normal range before the next expulsive efort. Fetal and obstetrical outcomes appear to be unafected whether pushing is coached or uncoached during second-stage labor (Bloom, 2006; Tuuli, 2012). Bloom and colleagues (2006) studied efects of actively coaching expulsive eforts in women without epidural analgesia. hey


Obstentrics_Williams

Obstentrics_Williams. is coached or uncoached during second-stage labor (Bloom, 2006; Tuuli, 2012). Bloom and colleagues (2006) studied efects of actively coaching expulsive eforts in women without epidural analgesia. hey reported that although the second stage was slightly shorter in coached women, no other maternal advantages were gained.


Obstentrics_Williams

Obstentrics_Williams. Several positions during the second stage have been recommended to augment pushing eforts. Eason and colleagues (2000) reviewed various posltlons and their efect on the incidence of perineal trauma. They found that the supported upright position had no advantages over the recumbent one. Upright positions include sitting, kneeling, squatting, or resting with the back at a 30-degree elevation. In women with regional analgesia, one recent randomized trial found higher vaginal delivery rates in those in a recumbent position compared with an upright one-41 versus 35 percent (The Epidural and Position Trial Collaborative Group, 2017). In women without epidural analgesia, Gupta (2017) in their review compared upright positions with supine or lithotom) positions and their efect on labor. Upright positions ofered a slightly shorter interval to delivery as well as fewer episiotomies and operative vaginal deliveries. However, rates of blood loss > 500 mL and perhaps of second-degree lacerations


Obstentrics_Williams

Obstentrics_Williams. positions ofered a slightly shorter interval to delivery as well as fewer episiotomies and operative vaginal deliveries. However, rates of blood loss > 500 mL and perhaps of second-degree lacerations were increased. Berghella and coworkers (2008) hypothesized that parity, less intense aortocaval compression, improved fetal alignment, and larger pelvic outlet diameters might explain these indings. In an earlier study, a 20-to 30-percent increase in the area of the pelvic outlet was noted with squatting compared with the supine position (Russell, 1969). Finally, Babayer and associates (1998) cautioned that prolonged sitting or squatting during the second stage may cause neuropathy of the common fibular (formerly common peroneal) nerve.


Obstentrics_Williams

Obstentrics_Williams. As the head descends through the pelvis, the perineum begins to bulge and the overlying skin becomes stretched. Now the scalp of the fetus may be visible through the vulvar opening. At this time, the woman and her fetus are prepared for delivery, which is described in Chapter 27 (p. 516). An orderly and systematic approach to labor management results in reproducible beneficial maternal and perinatal outcomes (lthabe, 2008). Several labor management protocols are subsequently presented. These include those from the National Maternity Hospital in Dublin, from the World Health Organization, and from Parkland Hospital.


Obstentrics_Williams

Obstentrics_Williams. In Dublin more than 30 years ago, O'Driscoll and associates (1984) pioneered the concept that a disciplined, standardized labor management protocol reduced the number of cesarean deliveries for dystocia. Their overall cesarean delivery rate was 5 percent in the 1970s and 1980s with such management. The approach is now referred to as active management of labor. Two of its components-amniotomy and oxytocinhave been widely used, especially in English-speaking countries outside the United States. With this protocol, labor is diagnosed when painful contractions are accompanied by complete cervical efacement, bloody "show," or ruptured membranes. Women with such indings are committed to delivery within 12 hours. Pelvic examination is performed each hour for the next 3 hours, and thereafter at 2-hour intervals. When dilation has not increased by at least 1 cm/hr, amniotomy is performed. Progress is again assessed at 2 hours, and high-dose oxytocin infusion, described in Chapter 26 (p. 509),


Obstentrics_Williams

Obstentrics_Williams. intervals. When dilation has not increased by at least 1 cm/hr, amniotomy is performed. Progress is again assessed at 2 hours, and high-dose oxytocin infusion, described in Chapter 26 (p. 509), is started unless dilation of at least 1 cm/hr is attained. Women are constantly attended by midwives. If membranes rupture before admission, oxytocin is begun for no progress at the I-hour mark.


Obstentrics_Williams

Obstentrics_Williams. such active management with their "traditional" approach to cago. hey randomly assigned 705 nulliparas with uncompli cated pregnancies in spontaneous labor at term. he cesarean delivery rate was significantly lower with active versus tradi tional management-10.5 versus 14.1 percent, respectively. Subsequent studies did not show this. Wei and associates tion in cesarean delivery rates when active management of labor was compared with standard care. Frigoletto and coworkers (1995) reported another randomized trial with 1934 nullipa rous women at Brigham and Women's Hospital in Boston. ened labor, it did not afect the cesarean delivery rate. hese observations have since been reported by others (Brown, 2013).


Obstentrics_Williams

Obstentrics_Williams. A partograph was designed by the World Health Organization (WHO) for use in developing countries (Dujardin, 1992). According to Orji (2008), the partograph is similar for nulliparas and multiparas. Labor is divided into a latent phase, which should last no longer than 8 hours, and an active phase. The active phase starts at 3 cm dilation, and progress should be no slower than 1 cm/hr. A 4-hour wait is recommended before intervention when the active phase is slow. Labor is graphed, and analysis includes use of alert and action lines. Lavender and colleagues (2006) randomized 3000 nulliparous women to labor interventions at 2 hours versus 4 hours as recommended by WH O. Their cesarean delivery rate was unafected, and they concluded that interventions such as amniotomy and oxytocin were needlessly increased using the 2-hour time interval. From their Cochrane Database review, Lavender and associates (2013) do not recommend use of the partograph for standard labor management.


Obstentrics_Williams

Obstentrics_Williams. At Parkland Hospital, women are admitted if active labor is diagnosed or if ruptured membranes are conirmed. Labor is defined as cervical dilation of 3 to 4 cm or more in the presence of uterine contractions. Management guidelines direct that a pelvic examination be performed approximately every 2 hours. Inefective labor is suspected when the cervix does not dilate within approximately 2 hours of admission. Amniotomy is then performed, and labor progress determined at the next 2-hour evaluation. In women whose labors do not progress, an intrauterine pressure catheter is placed to assess uterine function. Hypotonic contractions and no cervical dilation after an additional 2 to 3 hours result in stimulation of labor using the high-dose oxytocin regimen described in Chapter 26 (p. 509). The goal is uterine activity of 200 to 250 Montevideo units for 2 to 4 hours before dystocia can be diagnosed. If hypotonic contractions are strongly suspected, internal monitors may be placed with


Obstentrics_Williams

Obstentrics_Williams. The goal is uterine activity of 200 to 250 Montevideo units for 2 to 4 hours before dystocia can be diagnosed. If hypotonic contractions are strongly suspected, internal monitors may be placed with amniotomy and again cervical change and contraction pattern are assessed in 2 hours. Conirmation of deicient Montevideo units at that time may prompt oxytocin augmentation for maternal or fetal indications.


Obstentrics_Williams

Obstentrics_Williams. Dilation rates of 1 to 2 cm/hr are accepted as evidence of progress after satisfactory uterine activity has been established with oxytocin. This can require up to 8 hours or more before cesarean delivery is performed for dystocia. The cumulative time required to efect this stepwise management approach permits many women to establish efective labor. This management protocol has been evaluated in more than 20,000 women with uncomplicated pregnancies. Importantly, these labor interventions and the relatively infrequent use of cesarean delivery did not jeopardize the fetus-newborn. Adams SS, Eberhard-Gran M, Eskild A: Fear of childbirth and duration of labour: a study of 2206 women with intended vaginal delivery. BJOG 119(10):1238,r2012 Alexander JM, Sharma SK, Mcintire DD, et al: Epidural analgesia lengthens the Friedman active phase of labor. Obstet Gynecol 100:46,r2002


Obstentrics_Williams

Obstentrics_Williams. Alexander JM, Sharma SK, Mcintire DD, et al: Epidural analgesia lengthens the Friedman active phase of labor. Obstet Gynecol 100:46,r2002 Althabe F, Buekens P, Bergel E, et al: A behavioral intervention to improve obstetrical care. N Engl J Med 358:1929, 2008 American Academy of Pediatrics and the American College of Obstetricians and Gynecologists: Guidelines for Perinatal Care, 8th ed. Elk Grove Village, AAP, 2017 American College of Obstetricians and Gynecologists: Obstetric forceps. Committee Opinion 71, August 1989 American College of Obstetricians and Gynecologists: Hospital-based triage of obstetric patients. Committee Opinion No. 667, July 2016a American College of Obstetricians and Gynecologists: Oral intake during labor. Committee Opinion No. 441, September 2009, Reairmed 2016b American College of Obstetricians and Gynecologists: Obstetric analgesia and anesthesia. Committee Opinion No. 177, April 2017


Obstentrics_Williams

Obstentrics_Williams. American College of Obstetricians and Gynecologists, Society for MaternalFetal Medicine: Safe prevention of the primaty cesarean delivery. Obstetric Care Consensus No. I, March 2014, Reairmed 2016c Babayer M, Bodack MP, Creatura C: Common peroneal neuropathy secondary to squatting during childbirth. Obstet Gynecol 91 :830, 1998 Bailit JL, Dierker L, Blanchard MH, et al: Outcomes of women presenting in active versus latent phase of spontaneous labor. Obstet Gynecol 105:77, 2005 Berghella V, Baxter JK, Chauhan SP: Evidence-based labor and delivery management. Am J Obstet Gynecol 199:445,2008 Bloom SL, Casey BM, Schafer JI, et al: A randomized trial of coached versus uncoached maternal pushing during the second stage of labor. Am J Obstet Gyneco1r194:10,r2006 Bloom SL, Mcintire DO, Kelly MA, et al: Lack of efect of walking on labor and delivery. N Engl J Med 339:76, 1998


Obstentrics_Williams

Obstentrics_Williams. Bloom SL, Mcintire DO, Kelly MA, et al: Lack of efect of walking on labor and delivery. N Engl J Med 339:76, 1998 Brown He, Paranjothy S, Dowswell T, et al: Package of care for active management in labour for reducing caesarean section rates in low-risk women. Cochrane Database Syst Rev 9:CD004907, 2013 Cahill AG, DuY CR, Odibo AO, et al: Number of cervical examinations and risk of intrapartum maternal fever. Obstet Gynecol 119(6): 1096, 2012 Caldwell WE, Moloy HC, D'Esopo DA: A roentgenologic study of the mecha nism of engagement of the fetal head. Am J Obstet Gynecol 28:824, 1934 Calkins LA: he etiology of occiput presentations. Am J Obstet Gynecol 37:618, 1939 Carlan 5J, Wyble L, Lense J, et al: Fetal head molding: diagnosis by ultrasound and a review of the literature. J Perinatal 11r: 1 05, 1991 Carley ME, Carley JM, Vasdev G, et al: Factors that are associated with clinically overt postpartum urinary retention after vaginal delivery. Am J Obstet Gynecol 187:430,r2002


Obstentrics_Williams

Obstentrics_Williams. Carley ME, Carley JM, Vasdev G, et al: Factors that are associated with clinically overt postpartum urinary retention after vaginal delivery. Am J Obstet Gynecol 187:430,r2002 Carlhall S, Kallen K, Blomberg M: Maternal body mass index and duration of labor. Eur J Obstet Gynecol Reprod Bioi 171 (1):49, 2013 Carlson JM, Diehl JA, Murray MS, et al: Maternal position during parturition in normal labor. Obstet Gynecol 68:443, 1986 Carollo Te, Reuter JM, Galan HL, et al: Defining fetal station. Am J Obstet Gyneco1r191:1793,r2004 Chelmow D, Kilpatrick SJ, Laros RK J r: Maternal and neonatal outcomes after prolonged latent phase. Obstet Gynecol 81 :486, 1993 Chin JR, Henry E, Holmgren CM, et al: Maternal obesity and contraction strength in the first stage ofrlabor. m J Obstet :129.e1,r2012


Obstentrics_Williams

Obstentrics_Williams. Chin JR, Henry E, Holmgren CM, et al: Maternal obesity and contraction strength in the first stage ofrlabor. m J Obstet :129.e1,r2012 Doret M, Cartier R, Miribel J, et al: Premature preterm rupture of the membrane diagnosis in early pregnancy: PAMG-l and IGFBP-l detection in amniotic fluid with biochemical tests. Clin Biochem 46(18): 1816, 2013 Dujardin B, De Schampheleire I, Sene H, et al: Value of the alert and action lines on the partogram. Lancet 339: 1336, 1992 Dupuis 0, Silveira R, Zentner A, et al: Birth simulator: Reliability of transvaginal assessment of fetal head station as defined by the American College of Obstetricians and Gynecologists classification. Am J Obstet Gynecol 192:868, 2005 Eason E, Labrecque M, Wells G, et al: Preventing perineal trauma during childbirth: a systematic review. Obstet Gynecol 95:464, 2000


Obstentrics_Williams

Obstentrics_Williams. Eason E, Labrecque M, Wells G, et al: Preventing perineal trauma during childbirth: a systematic review. Obstet Gynecol 95:464, 2000 Edwards K, Reed CA, Villano KS, et l: Efect of hydration on spontaneous labor outcomes in nulliparous pregnant women: a multicenter randomized controlled trial comparing three methods. Am] PerinatoI31(6):455, 2014 Field NT, Piper ]M, Langer 0: he efect of maternal obesity on the accuracy offetal weight estimation. Obstet Gynecol 86(1): 1 02, 1995 Flynn vl, Kelly], Hollins G, et al: Ambulation in labour. BM] 2:591, 1978 Fox NS, Bhavsar V, Saltzman DH, et al: Influence of maternal body mass index on the clinical estimation of fetal weight in term pregnancies. Obstet Gynecol 113(3):641,o2009 Friedman E: The graphic analysis of labor. Am ] Obstet Gynecol 68: 1568, 1954 Friedman A: An objective approach to the diagnosis and management of abnormal labor. Bull N Y Acad Med 48:842, 1972


Obstentrics_Williams

Obstentrics_Williams. Friedman E: The graphic analysis of labor. Am ] Obstet Gynecol 68: 1568, 1954 Friedman A: An objective approach to the diagnosis and management of abnormal labor. Bull N Y Acad Med 48:842, 1972 Friedman A: Labor: Clinical Evaluation and Management, 2nd ed. New York, Appleton-Century-Crofts, 1978 Friedman A: Primigravid labor: a graphicostatistical analysis. Obstet Gynecol 6:567, 1955 Friedman A, Sachtleben MR: Amniotomy and the course of labor. Obstet GynecoIo22:755, 1963 Frigoletto FD ]r, Lieberman E, Lang]M, et al: A clinical trial of active management of labor. N Englo] Med 333:745, 1995 Gardberg M, Tuppurainen M: Anterior placental location predisposes for occiput posterior presentation near term. Acta Obstet Gynecol Scand 73: 151, 1994a Gardberg M, Tuppurainen M: Persistent occiput posterior presentation-a clinical problem. Acta Obstet Gynecol Scand 73:45, 1994b


Obstentrics_Williams

Obstentrics_Williams. Garite T], Weekso], Peters-Phair K, et al: A randomized controlled trial of the efect of increased intravenous hydration on the course of labor in nulliparous women. Am] Obstet GynecoIo183:1544, 2000 Goetzinger R, Odibo AO, Shanks L, et al: Clinical accuracy of estimated fetal weight in term pregnancies in a teaching hospital. ] Matern Fetal Neonatal Med 27(1):89,o2014 Graham]M ]r, Kumar A: Diagnosis and management of extensive vertex birth molding. Clin Pediatr (Phila) 45(7):672, 2006 Gupta ]K, Sood A, Hofmeyr G], et al: Position in the second stage of labour for women without epidural anaesthesia. Cochrane Database Syst Rev 5:CD002006, 2017 Hendricks CH, Brenner WE: Cardiovascular efects of oxytocic drugs used postpartum. Am] Obstet GynecoIo108:751, 1970 Herbst A, Kallen K: Time between membrane rupture and delivery and septicemia in term neonates. Obstet Gynecol 110:612,o2007


Obstentrics_Williams

Obstentrics_Williams. Herbst A, Kallen K: Time between membrane rupture and delivery and septicemia in term neonates. Obstet Gynecol 110:612,o2007 Igbinosa I, Moore FA 3rd, Johnson C, et al: Comparison of rapid immunoassays for rupture offetal membranes. BMC Pregnancy Childbirth 17(1): 128,2017 Kilpatrick S], Laros K ]r: Characteristics of normal labor. Obstet Gynecol 74:85, 1989 Kominiarek MA, Zhang ], VanVeldhuisen P, et al: Contemporary labor patterns: the impact of maternal body mass index. Am ] Obstet Gynecol 205:244.e1,o2011 Laughon SK, Branch W, Beaver ], et al: Changes in labor patterns over 50 years. Am] Obstet GynecoI206:419.e1.9, 2012 Lavender T, lirevic A, Walkinshaw S: Efect of diferent partogram action lines on birth outcomes. Obstet Gynecol 108:295,o2006 Lavender T, Hart A, Smyth M: Efect of partogram use on outcomes for women in spontaneous labour at term. Cochrane Database Syst Rev 7:CD005461,o20o13


Obstentrics_Williams

Obstentrics_Williams. Lavender T, Hart A, Smyth M: Efect of partogram use on outcomes for women in spontaneous labour at term. Cochrane Database Syst Rev 7:CD005461,o20o13 Lawrence A, Lewis L, Hofmeyr G], et al: Maternal positions and mobility during irst stage labour. Cochrane Database Syst Rev 10:CD003934, 2013 Leopold]: Conduct of normal births through external examination alone. Arch GynaekoIo45:337, 1894 L6pez-Zeno ]A, Peaceman M, Adashek ]A, et al: A controlled trial of a program for the active management of labor. N Engl] Med 326:450, 1992 Lupe P], Gross TL: Maternal upright posture and mobility in labor: a review. Obstet GynecoIo67:727, 1986 Lydon-Rochelle M, Albers L, Gowoda], et al: Accuracy of Leopold maneuvers in screening for malpresentation: a prospective study. Birth 20: 132, 1993 Musselwhite L, Faris P, Moore K, et al: Use of epidural anesthesia and the risk of acute postpartum urinary retention. Amo] Obstet Gynecol 196:472, 2007


Obstentrics_Williams

Obstentrics_Williams. Musselwhite L, Faris P, Moore K, et al: Use of epidural anesthesia and the risk of acute postpartum urinary retention. Amo] Obstet Gynecol 196:472, 2007 Nelson DB, McIntire DO, Leveno K]: False labor at term in singleton pregnancies: Discharge after a standardized assessment and perinatal outcomes. Obstet GynecoIo130(1):139, 2017 Noumi G, Collado-Khoury F, Bombard A, et al: Clinical and sonographic estimation of fetal weight performed in labor by residents. Am ] Obstet GynecoIo192:1407,o2005 Nygaard I: Pelvic loor recovery ater childbirth. Obstet Gynecol 125(3):529, 20o15 O'Driscoll K, Foley M, MacDonald 0: Active management of labor as an alternative to cesarean section for dystocia. Obstet Gynecol 63:485, 1984 Orji E: Evaluating progress of labor in nulliparas and multiparas using the modiied WHO partograph. Into] Gynaecol Obstet 102:249,o2008 Pates ]A, McIntire DO, Leveno K]: Uterine contractions preceding labor. Obstet Gynecol 110:566, 2007


Obstentrics_Williams

Obstentrics_Williams. Pates ]A, McIntire DO, Leveno K]: Uterine contractions preceding labor. Obstet Gynecol 110:566, 2007 Ramphul M, Ooi PV, Burke G, et al: Instrumental delivery and ultrasound: a multicentre randomised controlled trial of ultrasound assessment of the fetal head position versus standard care as an approach to prevent morbidity at instrumental delivery. B]OG 121(8):1029,o2014 Read ]A, Miller FC, Paul RH: Randomized trial of ambulation versus oxytocin for labor enhancement: a preliminary report. Am ] Obstet Gynecol 139(6):669, 1981 Robinson BK, Mapp DC, Bloom SL, et al: Increasing maternal body mass index and characteristics of the second stage of labor. Obstet Gynecol 118:1309,o2011 Russell ]G: Moulding of the pelvic outlet. ] Obstet Gynaecol Br Commonw 76:817,o1969 Saccone G, Berghella V: Antibiotic prophylaxis for term or near-term premature rupture of membranes: metaanalysis of randomized trials. Amo] Obstet Gynecol. 2015 May;212(5):627.e1


Obstentrics_Williams

Obstentrics_Williams. Saccone G, Berghella V: Antibiotic prophylaxis for term or near-term premature rupture of membranes: metaanalysis of randomized trials. Amo] Obstet Gynecol. 2015 May;212(5):627.e1 Segel SY, Carreno CA, Weiner MS, et al: Relationship between fetal station and successful vaginal delivery in nulliparous women. Am ] Perinatol 29:723,o2012 Shrivastava K, Garite T], Jenkins SM, et al: A randomized, double-blinded, controlled trial comparing parenteral normal saline with and without dextrose on the course oflabor in nulliparas. Amo] Obstet Gynecol 200(4):379. el,o2009 Sokol R], Stojkov ], Chik L, et al: Normal and abnormal labor progress: 1. A quantitative assessment and survey of the literature. ] Reprod Med 18:47, 1977 Soper DE, Mayhall CG, Dalton HP: Risk factors for imraamniotic infection: a prospective epidemiologic study. Am] Obstet GynecoIo161(3):562, 1989


Obstentrics_Williams

Obstentrics_Williams. Soper DE, Mayhall CG, Dalton HP: Risk factors for imraamniotic infection: a prospective epidemiologic study. Am] Obstet GynecoIo161(3):562, 1989 Staer-]ensen ], Siafarikas F, Hilde G, et al: Postpartum recovery of levator hiatus and bladder neck mobility in relation to pregnancy. Obstet Gynecol 125(3):531,o2015 Tuuli MG, Frey A, Odibo AO, et al: Immediate compared with delayed pushing in the second stage oflabor. Obstet Gynecol 120:660, 2012 Wei S, Wo BL, Qi HP, et al: Early amniotomy and early oxytocin for prevention of, or therapy for, delay in irst stage spontaneous labour compared with routine care. Cochrane Database Syst Rev 8:CD006794, 2013 Wiafe YA, Whitehead B, Venables H, et al: he efectiveness of intrapartum ultrasonography in assessing cervical dilatation, head station and position: a systematic review and meta-analysis. Ultrasound 24(4) :222, 2016


Obstentrics_Williams

Obstentrics_Williams. Williams M, hon MH, Studd ]W: A study of the beneits and acceptability of ambulation in spontaneous labor. B]OG 87: 122, 1980 Yamada H, Kishida T, Negishi H, et al: Silent premature rupture of membranes, detected and monitored serially by an AFP kit. ] Obstet Gynaecol Res 24:103, 1998 Zhango], Landy H], Branch OW, et al: Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116: 1281, 2010 DYSTOCIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 ABNORMALITIES OF THE EXPULSIVE FORCES ........ 442 PREMATURELY RUPTURED MEMBRANES AT TERM ... 447 PRECIPITOUS LABOR AND DELIVERY ............... 448 FETOPELVIC DISPROPORTION . . . . . . . . . . . . . . . . . . . . 448 PELVIC CAPACITY .............................. 448 FACE PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 450


Obstentrics_Williams

Obstentrics_Williams. FETOPELVIC DISPROPORTION . . . . . . . . . . . . . . . . . . . . 448 PELVIC CAPACITY .............................. 448 FACE PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 BROW PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . 452 TRANSVERSE LIE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452 COMPOUND PRESENTATION ..................... 454 COMPLICATIONS WITH DYSTOCIA. . . . . . . . . . . . . . . . . 454 ... pains become less requent and less intense, although giving rise to quite as much or even more suering than previousy. At the same time, the cervix, which was becoming obliterated and dilated in a satiactory manner, ceases to make urther proress and labour apparenty comes to a stanstill. -J.


Obstentrics_Williams

Obstentrics_Williams. he term dystocia as described by Williams in the irst edition of this text still applies today. It literally means dficult labor and is characterized by abnormally slow labor progress. Similar to the factors described by Williams, dystocia arises from three distinct abnormality categories. First, uterine contractions may be insuiciently strong or inappropriately coordinated to eface and dilate the cevix-uterine dyunction. lso, voluntary maternal muscle efort during second-stage labor may be inadequate. Second, fetal abnormalities of presentation, position, or anatomy may slow progress. Last, structural changes can contract the maternal bony pelvis. Or, soft tissue abnormalities of the reproductive tract may form an obstacle to fetal descent. More simply, these alterations can be mechanistically simplified into three categories that include abnormalities of the powers-uterine contractility and maternal expulsive efort; of the passenger-the fetus; and of the passage-the pelvis and lower


Obstentrics_Williams

Obstentrics_Williams. simplified into three categories that include abnormalities of the powers-uterine contractility and maternal expulsive efort; of the passenger-the fetus; and of the passage-the pelvis and lower reproductive tract.


Obstentrics_Williams

Obstentrics_Williams. 23-1 oten interact singly or in combination to produce dysfunctional labor. Commonly used expressions today such as cephalopelvic disproportion and ailure to progress are used to describe inefective labors. Of these, TABLE 23-1. Common Clinical Findings in Women with Ineffective Labor Inadequate cervical dilation or fetal descent: Fetopelvic disproportion:


Obstentrics_Williams

Obstentrics_Williams. Inadequate pelvic capacity Malpresentation or pOSition of the fetus Abnormal fetal anatomy cephalopelvic disproportion is a term that came into use before the 20th century to describe obstructed labor resulting from disparity between the fetal head size and maternal pelvis. But, the term originated at a time when the main indication for cesarean delivery was overt pelvic contracture due to rickets (0lah, 1994). Such absolute disproportion is now rare, and most cases result from malposition of the fetal head within the pelvis (asynclitism) or from inefective uterine contractions. True disproportion is a tenuous diagnosis because many women who undergo cesarean delivery for this reason subsequently deliver even larger newborns vaginally in subsequent pregnancies. A second phrase, ailure to progress in either spontaneous or stimulated labor, has become an increasingly popular description of inefectual labor. his term reflects lack of progressive cervical dilation or lack of fetal


Obstentrics_Williams

Obstentrics_Williams. to progress in either spontaneous or stimulated labor, has become an increasingly popular description of inefectual labor. his term reflects lack of progressive cervical dilation or lack of fetal descent. Neither of these two terms is specific.


Obstentrics_Williams

Obstentrics_Williams. • Mechanisms of Dystocia At the end of pregnancy, the fetal head encounters a relatively thick lower uterine segment and undilated cervix. With the . onset of labor, the factors influencing progress are uterine contractions, cervical resistance, and the forward pressure exerted by the leading fetal part. Ater complete cervical dilation, the mechanical relationship between the fetal head size and position and the pelvic capacity, namelyetopelvic proportion, becomes clearer as the fetus attempts to descend. Because of this, abnormalities in fetopelvic proportions become more apparent once the second stage is reached. Uterine muscle malfunction can result from uterine overdistention, obstructed labor, or both. Thus, infective labor is generaly accepted as a possible warning sign of etopelvic disproportion.


Obstentrics_Williams

Obstentrics_Williams. Uterine muscle malfunction can result from uterine overdistention, obstructed labor, or both. Thus, infective labor is generaly accepted as a possible warning sign of etopelvic disproportion. Although artificial separation of labor abnormalities into pure uterine dysfunction andetopelvic disproportion simplifies classification, it is an incomplete characterization because these two abnormalities are closely interlinked. Indeed, the bony pelvis rarely limits vaginal delivery. In the absence of objective means of precisely distinguishing these two causes of labor failure, clinicians must rely on a trial of labor to determine if labor can be successful in efecting vaginal delivery.


Obstentrics_Williams

Obstentrics_Williams. Cervical dilation as well as propulsion and expulsion of the fetus are brought about by uterine contractions. During second-stage labor, these contractions are then reinforced by voluntary or involuntary muscular action of the abdominal wall-"pushing." The diagnosis of uterine dysfunction in the latent phase is diicult and sometimes can be made only in retrospect. Women who are not yet in active labor commonly are erroneously treated for this dysfunction. Beginning in the 1960s, at least three significant advances have aided treatment of uterine dysfunction. First is the realization that undue labor prolongation may contribute to maternal and perinatal morbidity and mortality rates. Second, dilute intravenous infusion of oxytocin is administered to treat certain types of uterine dysfunction. Last, cesarean delivery is selected rather than diicult midforceps delivery when oxytocin fails or its use is inappropriate. • Types of Uterine Dysfunction


Obstentrics_Williams

Obstentrics_Williams. Reynolds and coworkers (1948) emphasized that uterine contractions of normal labor are characterized by a gradient of myometrial activity. These forces are greatest and last longest at the fundus-considered fundal dominance-and they diminish toward the cervix. Caldeyro-Barcia and colleagues (1950) from Montevideo, Uruguay, inserted small balloons into the myometrium at various levels (Chap. 24, p. 478). hey reported that in addition to a gradient of activity, the onset of the contractions difered in the fundus, midzone, and lower uterine segments. Larks (1960) described the stimulus as starting in one cornu and then several milliseconds later in the other. he excitation waves then join and sweep over the fundus and down the uterus. Normal spontaneous contractions often exert pressures approximating 60 mm Hg (Hendricks, 1959). Even so, the Montevideo group ascertained that the lower limit of contraction pressure required to dilate the cervix is 15 mm Hg.


Obstentrics_Williams

Obstentrics_Williams. From these observations, two physiological types of uterine dysfunction are defined. In the more common hypotonic uterine dyunction, there is no basal hypertonus, and uterine contractions have a normal gradient pattern (synchronous). However, pressure during a contraction is insuicient to dilate the cervix. In the second type, hypertonic uterine dysunction or incoordinate uterine dyunction, either basal tone is elevated appreciably or the pressure gradient is distorted. Gradient distortion may result from more forceful contraction of the uterine midsegment than the fundus, from complete asynchrony of the impulses originating in each cornu, or from a combination of these two.


Obstentrics_Williams

Obstentrics_Williams. hese just-described types of uterine dysfunction can in turn lead to labor abnormalities (Table 23-2). First, the latent phase may be prolonged, which is defined as exceeding 20 hours in the nullipara and 14 hours in the multipara. In some, uterine contractions cease, suggesting false labor. In the remainder, an abnormally long latent phase persists and is often treated with oxytocin stimulation. In active labor, disorders are divided into slower-than-normal progress-a protraction disorder-or complete cessation of progress-an arrest disorder. Terms presented in Table 23-2 and their diagnostic criteria more precisely describe abnormal labor. To be diagnosed with either of these, a woman must be in the active phase of labor, which is defined by cervical change.


Obstentrics_Williams

Obstentrics_Williams. hese criteria and management of abnormal labor have recently undergone a sea change. In 2014, the American College of Obstetricians and Gynecologists and the Society for vIaternal-Fetal Medicine issued their irst Obstetric Care Consensus titled Sae Prevention of the Primary Cesarean Delivery. It was reairmed in 2016. his consensus statement was a response to concerns that cesarean delivery was overused in the United States. Namely, approximately one in three women who give birth each year undergoes this surgery (Fig. 31-1, p. 592). New recommendations from the Consensus Committee are based on TABLE 23-2. Abnormal Labor Patterns, Diagnostic Criteria, and Methods of Treatment Arrest Disorders Prolonged deceleration phase Secondary arrest of dilation Arrest of descent Failure of descent CPo = cephalopelvic disproportion. Modified from Cohen, 1983. <l.2scm/hr 1.5 cm/hr Expectant and Cesarean delivery for CPD >2 hr >2 hr Evaluate for cpo: > 1 hr > 1 hr CPO: cesarean


Obstentrics_Williams

Obstentrics_Williams. CPo = cephalopelvic disproportion. Modified from Cohen, 1983. <l.2scm/hr 1.5 cm/hr Expectant and Cesarean delivery for CPD >2 hr >2 hr Evaluate for cpo: > 1 hr > 1 hr CPO: cesarean No descent in deceleration No CPD: oxytocin "more recent data used to revise the definition of contemporary normal labor progress" and reflect a signiicant revision of the preexisting understanding of abnormal labor.


Obstentrics_Williams

Obstentrics_Williams. Active-Phase Protraction. Of active-phase disorders, protraction disorders are less well described, and the time necessary before diagnosing slow progress is undefined. he Wodd Health Organization (1994) has proposed a labor management partograph in which protraction is defined as < 1 cm/ hr cervical dilation for a minimum of 4 hours. hese criteria were adapted from those of Cohen and Friedman (1983) and shown in Table 23-2. For this disorder, observation for further progress is appropriate treatment. If insuicient Montevideo units are noted, oxytocin augmentation is initiated. According to the Consensus Committee (2016), slow but progressive irststage labor should not be an indication for cesarean delivery.


Obstentrics_Williams

Obstentrics_Williams. Active-Phase Arrest. Handa and Laros (1993) diagnosed active-phase arrest, deined as no dilation for 2 hours or more, in 5 percent of term nulliparas. This incidence has not changed since the 1950s (Friedman, 1978). Inadequate uterine contractions, deined as less than 180 Montevideo units, calculated as shown in Figure 23-1, were diagnosed in 80 percent of women with active-phase arrest. Hauth and coworkers (1986, 1991) FIGURE 23-' Montevideo units are calculated by subtracting the baseline uterine pressure from the peak contraction pressure for each contraction in a 1 O-minute window and adding the pressures generated by each contraction. In the example shown, there were five contractions, producing pressure changes of 52,50,47,44, and 49 mm Hg, respectively. The sum of these five contractions is 242 Montevideo Final study sample n 62,41e5


Obstentrics_Williams

Obstentrics_Williams. Final study sample n 62,41e5 FIGURE 23-2 Study cohort for the analysis of spontaneous labor in the Consortium on Safe Labor study. NICU = neonatal intensive care unit. (Data from Zhang, 2010.) reported that when labor is efectively induced or augmented with oxytocin, 90 percent of women achieve 200 to 225 Montevideo units, and 40 percent achieve at least 300 Montevideo units. hese results suggest that certain minimums of uterine activity should be achieved before performing cesarean delivery for dystocia.


Obstentrics_Williams

Obstentrics_Williams. Other criteria should also be met. First, the latent phase should be completed, and the cervix is dilated ::4 cm. Also, a uterine contraction pattern of 200 Montevideo units or more in a 10-minute period has been present for 2 or more hours without cervical change. Rouse and associates (1999) challenged the "2-hour rule" on the grounds that a longer time, that is, at least 4 hours, is necessary before concluding that the active phase of labor has failed. We agree. The Consensus Committee (2016) has expanded the criteria, as described next. Obstetric Care Consensus Committee. There are four recom mendations by the Consensus Committee (2016) applicable to management of the irst-stage labor. The irst admonishes against cesarean delivery in the latent phase of labor. Speciically, a prolonged latent phase is not an indication for cesarean delivery. This guideline is not new and is traceable to the work of Friedman (1954), on which traditional tenets are based.


Obstentrics_Williams

Obstentrics_Williams. The second directive, too, is conventional practice. It recommends against cesarean delivery if labor is progressive but slow-aprotraction disorder. This instance is typically managed with observation, assessment of uterine activity, and stimulation of contractions as needed. A third instruction addresses the cervical dilation threshold that serves to herald active labor. Namely, a cervical dilation of 6 cm-not 4 cm-is now the recommended threshold. Thus, before this threshold, standards for active-phase progress should not be applied. A fourth stipulation notes that cesarean delivery for activephase arrest "should be reserved for women at or beyond 6 cm of dilation with ruptured membranes who fail to progress despite 4 hours of adequate uterine activity, or at least 6 hours of oxytocin administration with inadequate contractions and no cervical change."


Obstentrics_Williams

Obstentrics_Williams. According to the Consensus Committee (2016), the "6-cm rule" stems from labor data from the Consortium on Safe Labor study (Zhang, 2010). This study derived its numbers from a retrospective observational dataset built from abstracted labor and delivery information from 19 hospitals across the United States. Various statistical methods and heavy manipulations of these numbers were used (Cohen, 2015b). As shown in Figure 23-2, a total of 62,415 women were analyzed after excluding all women with cesarean deliveries or asphyxiated newborns. The Consensus Committee (2016) was explicit that "the Consortium on Safe Labor data, rather than the standards proposed by Friedman should inform evidence-based labor management." Described in Chapter 21 (p. 432), the latter are labor curves that have been used since irst proposed by Friedman (1955).


Obstentrics_Williams

Obstentrics_Williams. Critics of the Consensus Committee (2016) recommendations note that the Consortium on Safe Labor data were derived from clinical settings with a net cesarean rate of 30 percent. hus, adherence to the new recommendations may fail to achieve desired cesarean rate reductions. Also, the study lacked a focus on neonatal safety, given that all the asphyxiated neonates were excluded. Supporters note that the study of prolonged first-stage labors by Cheng and coworkers (2010) found higher rates of cesarean delivery and chorioamnionitis but not higher rates of neonatal morbidity. However, Harper and associates (2014) analyzed maternal and neonatal adverse outcomes related to first-stage labor lengths. In 5030 women, first-stage labor durations were divided into those <90th percentile or those ::90th percentile, with incremental increases thereafter. These authors concluded that a longer irst-stage labor was associated with maternal and neonatal complications and that these should be balanced


Obstentrics_Williams

Obstentrics_Williams. percentile, with incremental increases thereafter. These authors concluded that a longer irst-stage labor was associated with maternal and neonatal complications and that these should be balanced against the risks of cesarean delivery. his concern for adverse fetal and maternal efects resulting from the new Consensus Committee guidelines was echoed by Cohen and Friedman (2015a,b).


Obstentrics_Williams

Obstentrics_Williams. Spontaneous onset of labor, Singletons, cephalic n = 98,169 Excluded: 23,280 cesarean births Vaginal delivery n = 74,889 women TABLE 23-3. Comparison of Study Populations Analyzed to Define Normal Labor Curves Year of data collection Early 1950s 1992-1996 Caudal/epidural analgesia (%) 8 48 Oxytocin augmentation (%) 9 50 aTripler Army Hospital. Data from Friedman, 1955; Zhang, 2002. TABLE 23-4. Rate of Change at Each Stage of Cervical Dilation Cervical Dilation Rate of Cervical Dilation 2 0.3 (0.1, 1.8) 3 0.4 (0.1,s1.8) 4 0.6 (0.2, 1 .8) 5 1.2 (0.3, 5.0) 6 1.7 (0.5, 6.3) 7 2.2 (0.7, 7.1) 8 2.4 (0.8, 7.7) 9 2.4 (0.7, 8.3) aMedian (5th and 95th percentiles). Data from Zhang, 2002.


Obstentrics_Williams

Obstentrics_Williams. Another caveat notes that the eicacy of these recommendations to achieve their primary goal is limited. In support, one retrospective cohort study of 200 women undergoing induction or augmentation before and 200 ater guideline changes found a cesarean delivery rate drop from 35 to 25 percent (WilsonLeedy, 2016). However, although the study was not powered to assess adverse neonatal outcomes, nonsigniicant but higher rates of umbilical artery gases with pH <7 and base deficit > 12 mmollL were noted in the postguideline group (Marte, 2016). In another evaluation of outcomes before and ater guideline implementation, cesarean delivery rates were unchanged. Overall, there were no associations between length of arrest and maternal or neonatal morbidity, but neonatal respiratory morbidity rates rose in newborns of women with longer periods of arrested dilation (Rosenbloom, 2017). Thus, additional studies are needed to define risks and beneits of the new guidelines.


Obstentrics_Williams

Obstentrics_Williams. Background for the 6-cm Rule. Review of selected publications helps explain the Consensus Committee (2016) evolution to a 6-cm rule. First, Zhang and coworkers (2002) compared study populations from one report by Friedman (1955) with one from 1992 to 1996 at TripIer Army Hospital, Hawaii (Table 23-3). The Friedman labor curves relected women in spontaneous labor with infrequent use of neuraxial labor analgesia or �: 6.2 0).;; Duration of labor (hours)


Obstentrics_Williams

Obstentrics_Williams. Duration of labor (hours) FIGURE 23-3 Cervical dilation curves. (From Friedman (1955) and Zhang (2002).) oxytocin augmentation. In contrast, in the TripIer cohort, approximately 50 percent of women had neuraxial analgesia or augmentation. The rate of cervical change for the ensuing hour at each cervical dilation between 2 and 9 cm in the T ripIer group is shown in Table 23-4. Progress is slow between 4 and 6 cm but accelerates thereafter. his could reasonably be interpreted as the active phase beginning at 6 cm. Shown in Figure 23-3 are the labor curves for Friedman (1955) compared to the TripIer cohort. These difer in a flattening of the active phase beginning at 3 to 4 cm in the TripIer group. his is consistent with the labor results obtained in the Safe Labor Consortium study (Zhang, 2010). Namely, the 6-cm rule for active labor derives from a slowing of the rate or lattening of the slope of cervical change in irst-stage labor.


Obstentrics_Williams

Obstentrics_Williams. N euraxial analgesia delays the active phase of spontaneous labor and flattens the slope. For example, Gambling and associates (1998) compared combined spinal epidural (CSE) labor analgesia against intermittent intravenous (IV) boluses of 50 mg meperidine in 1223 nulliparas in spontaneous labor at term. The active phase of labor was diagnosed when cervical dilation was 4 cm in the presence of regular uterine contractions. s shown in Table 23-5, mean cervical dilation at first pain aAdministered as intermittent intravenous boluses. bMedian value. CPresented as number (%). dpresented as mean ± standard deviation. Data from Gambling, 1998. TABLE 23-6. 9000 Women Undergoing Primary Cesarean Delivery for Dystocia Percentage of Women with Noted Median (1st, 3rd 6 cm (5,s8) Augmentation to delivery time 9.3 hr (6, 13) Data from Alexander, 2003.


Obstentrics_Williams

Obstentrics_Williams. Percentage of Women with Noted Median (1st, 3rd 6 cm (5,s8) Augmentation to delivery time 9.3 hr (6, 13) Data from Alexander, 2003. relief was 5 cm in both study groups. Oxytocin augmentation rates were signiicantly greater in the CSE group. Also, the first analgesia-to-delivery interval was lengthened (5 versus 4 hours). However, cesarean delivery rates did not difer significantly. Importantly, the efect of neuraxial analgesia to slow activephase labor should not negatively afect use of neuraxial pain relie. As described in Chapter 25 (p. 495), investigators at Parkland Hospital completed five randomized trials involving a total of 2703 nulliparas in spontaneous labor at term (Sharma, 2004). Various neuraxial techniques were compared with meperidine for pain relief. First-stage labor was significantly lengthened with neuraxial analgesia (8.1 versus 6.6 hours) but cesarean delivery rates for dystocia were unafected (9.i1 versus 8.1 percent).


Obstentrics_Williams

Obstentrics_Williams. In sum, neuraxial analgesia slows the active phase of firststage labor. his currently is empirically corrected by augmentation of uterine contractions. Thus, recommendations of the Consensus Committee regarding protraction disorders are correct. Second, the Consensus Committee (2016) suggests that cesarean deliveries for dystocia are being done before 6 cm cervical dilation. However, there is good reason to believe that all of the Committee's first-stage recommendations are actually already empirically in use but are concurrent with an overall cesarean delivery rate in excess of 30 percent. For example, Table 23-6 lists labor characteristics in 9000 women with primary cesarean deliveries for dystocia at 13 university hospitals between 1999 and 2000 (Alexander, 2003). Notably, the median cervical dilation at the time ofcesarean for dystocia was 6 cm. Moreover, Figure 23-4 depicts primary cesarean delivery rates for dystocia at Parkland Hospital between 1988 and 2017. The rate has not


Obstentrics_Williams

Obstentrics_Williams. cervical dilation at the time ofcesarean for dystocia was 6 cm. Moreover, Figure 23-4 depicts primary cesarean delivery rates for dystocia at Parkland Hospital between 1988 and 2017. The rate has not changed significantly in 28 years. Thus, Consensus Committee (2016) guidelines may fail to prevent additional cesareans for dystocia. Again, additional studies are needed.


Obstentrics_Williams

Obstentrics_Williams. Fetal descent largely follows complete dilation. Moreover, the second stage incorporates many of the cardinal movements necessary for the fetus to negotiate the birth canal (Chap. 22, p. 428). Accordingly, disproportion ofthe fetus and pelvis frequently becomes apparent during second-stage labor. Similar to irst-stage labor, time boundaries have been supported to limit second-stage duration to minimize adverse maternal and fetal outcomes. he second stage in nulliparas is limited to 2 hours and extended to 3 hours when regional analgesia is used. For multiparas, 1 hour is the limit, extended to 2 hours with regional analgesia.


Obstentrics_Williams

Obstentrics_Williams. Cohen (1977) investigated the fetal efects of second-stage labor length at Beth Israel Hospital. He included 4403 term nulliparas in whom electronic fetal heart rate monitoring was performed. he neonatal mortality rate was not increased in women whose second-stage labor exceeded 2 hours. Epidural analgesiawas used commonly, and this likely accounted for the large number of pregnancies with a prolonged second stage. These data inluenced decisions to permit an additional hour for the second stage when regional analgesia is used. Menticoglou and coworkers (1995a,b) also challenged the prevailing dicta on second-stage duration. Their concern stemmed from grave neonatal injuries associated with forceps rotations to shorten second-stage labor. As a result, they allowed a longer second stage to decrease the operative vaginal delivery rate. Between 1988 and 1992, second-stage labor exceeded 2 hours in a fourth of 6041 nulliparas at term. Labor epidural 4 0)) 3.�i0C)E 20:0E)0). 0


Obstentrics_Williams

Obstentrics_Williams. Year of delivery FIGURE 23-4 Primary caesarean delivery rates for dystocia in lowrisk women at term at Parkland Hospital from 1988 to 2017. analgesia was used in 55 percent. he length of the second stage, even in those lasting up to 6 hours or more, was not related to neonatal outcome. hese results were attributed to careful use of electronic monitoring and scalp pH measurements. hese investigators concluded that there is no compelling reason to intervene with a possibly diicult forceps or vacuum extraction because a certain number of hours have elapsed. hey observed, however, that after 3 hours in the second stage, delivery by cesarean or other operative method increased progressively. By 5 hours, the prospects for spontaneous delivery in the subse quent hour were only 10 to 15 percent.


Obstentrics_Williams

Obstentrics_Williams. Newer guidelines have been promoted by the Consensus Com mittee (2016) for second-stage labor. These recommend allowing a nullipara to push for at least 3 hours and a multipara to push for at least 2 hours before second-stage labor arrest is diagnosed. One caveat is that maternal and fetal status should be reassuring. hese authors provide options to these times before cesarean deliv ery is performed. Namely, longer durations may be appropriate as long as progress is documented. Also, a speciic maximal length of undergo operative delivery has not been identiied.


Obstentrics_Williams

Obstentrics_Williams. Intuitively, the goal to lower cesarean delivery rates is best balanced with one to ensure neonatal safety. And, it is problematic that no robust data on neonatal outcomes support the safety of allowing prolonged second-stage labor. Data from many evaluations reveal that serious newborn consequences attend second-stage labors longer than 3 hours (Allen, 2009; Bleich, 2012; Laughon, 2014; Leveno, 2016; Rosenbloom, 2017). Other data, when adjusted for labor variables, show no diference in neonatal complications for these longer second stages (Cheng, 2004; Le Ray, 2009; Rouse, 2009). Grobman and colleagues (2016) have argued that the absolute number of such adverse outcomes is small and "overall outcomes remain good." hat said, some of the complications are severe. Thus, to fully ascertain specific efect of these guidelines on morbidity rates, randomized controlled trials are needed.


Obstentrics_Williams

Obstentrics_Williams. It is possible that prolonged first-stage labor presages that with the second stage. Nelson and associates (20l3) studied the relationships between the lengths of the irst and second stages of labor in 12,523 nulliparas at term delivered at Parkland Hospital. The second stage signiicantly lengthened concomitantly with increasing irst-stage duration. The 95th percentile was 15.6 and 2.9 hours for the first and second stages, respectively. Women with first stages lasting longer than 15.6 hours (>95th percentile) had a 16-percent rate of second-stage labor lasting 3 hours (95th percentile). his compared with a 4.5-percent rate of prolonged second stages in women with irst-stage labors lasting <95th percentile.


Obstentrics_Williams

Obstentrics_Williams. With ull cervical dilation, most women cannot resist the urge to "bear down" or "push" each time the uterus contracts (Chap. 22, p. 438). he combined force created by contractions of the uterus and abdominal musculature propels the fetus downward. At times, force created by abdominal musculature is compromised suiciently to slow or even prevent spontaneous vaginal delivery. Heavy sedation or regional analgesia may reduce the reflex urge to push and may impair the ability to contract abdominal muscles efectively. In other instances, the inherent urge to push is overridden by the intense pain created by bearing down. Two approaches to second-stage pushing in women with epidural analgesia have yielded contradictory results. The irst advocates pushing forcefully with contractions ater complete dilation, regardless of the urge to push. With the second, analgesia inusion is stopped and pushing begins only ater the woman regains the sensory urge to bear down. Fraser and coworkers (2000)


Obstentrics_Williams

Obstentrics_Williams. dilation, regardless of the urge to push. With the second, analgesia inusion is stopped and pushing begins only ater the woman regains the sensory urge to bear down. Fraser and coworkers (2000) found that delayed pushing reduced diicult operative deliveries, whereas Manyonda and associates (1990) reported the opposite. Hansen and colleagues (2002) randomly assigned 252 women with epidural analgesia to one of the two approaches. No adverse maternal or neonatal outcomes were linked to delayed pushing despite signiicantly prolonging second-stage labor. Plunkett and coworkers (2003), in a similar study, confirmed these indings.


Obstentrics_Williams

Obstentrics_Williams. Descent of the leading edge of the presenting part to the level of the ischial spines (0 station) is deined as engagement. A higher station at the onset of labor is signiicantly linked with subsequent dystocia (Friedman, 1965, 1976; Handa, 1993). Roshanfekr and associates (1999) analyzed fetal station in 803 nulliparas at term in active labor. At admission, the third with the fetal head at or below 0 station had a 5-percent cesarean delivery rate. This compared with a 14-percent rate for those with higher stations. The prognosis for dystocia, however, was not related to incrementally higher fetal head stations above the pelvic midplane (0 station). Importantly, 86 percent of nulliparous women without fetal head engagement at diagnosis of active labor delivered vaginally. hese observations apply especially for parous women because the head typically descends later in labor.


Obstentrics_Williams

Obstentrics_Williams. Various labor factors have been implicated as causes of uterine dysfunction. As described, neuraxial analgesia can slow labor and has been associated with lengthening both first and second stages of labor and slowing the rate of fetal descent.


Obstentrics_Williams

Obstentrics_Williams. Chorioamnionitis is associated with prolonged labor, and some clinicians have suggested that this maternal intrapartum infection itself contributes to abnormal uterine activity. Satin and coworkers (1992) studied the efects of chorioamnionitis on oxytocin stimulation in 266 pregnancies. Infection diagnosed late in labor was found to be a marker of cesarean delivery performed for dystocia. Specifically, 40 percent of women developing chorioamnionitis after requiring oxytocin for dysfunctional labor later required cesarean delivery for dystocia. However, this was not a marker in women diagnosed as having chorioamnionitis early in labor. It is likely that uterine infection in this clinical setting is a consequence of dysfunctional, prolonged labor rather than a cause of dystocia.


Obstentrics_Williams

Obstentrics_Williams. Membrane rupture at term without spontaneous uterine contractions complicates approximately 8 percent of pregnancies. In the past, labor stimulation was initiated if contractions did not begin ater 6 to 12 hours. Practice-changing research included that of Hannah (1996) and Peleg (1999) and their associates, who enrolled a total of 5042 pregnancies with ruptured membranes in a randomized investigation. hey measured the efects of induction versus expectant management and also compared induction using intravenous oxytocin with that using prostaglandin E2 gel. There were approximately 1200 pregnancies in each of the four study arms. They concluded that labor induction with intravenous oxtocin was preferred management. This was based on signiicantly fewer intrapartum and postpartum infections in women whose labor was induced. There were no significant differences in cesarean delivery rates. Subsequent analysis by Hannah and coworkers (2000) indicated higher rates of adverse outcomes when


Obstentrics_Williams

Obstentrics_Williams. in women whose labor was induced. There were no significant differences in cesarean delivery rates. Subsequent analysis by Hannah and coworkers (2000) indicated higher rates of adverse outcomes when expectant management at home was compared with in-hospital observation. Mozurkewich and associates (2009) reported lower rates of chorioamnionitis, metritis, and neonatal intensive care unit admissions for women with term ruptured membranes whose labors were induced compared with those managed expectantly. At Parkland Hospital, labor is induced soon ater admission when ruptured membranes are conirmed at term. In those with hypotonic contractions or with advanced cervical dilation, oxytocin is selected to lower potential hyperstimulation risk. In those with an unfavorable cervix and no or few contraction, prostaglandin E1 (misoprostol) is chosen to promote cervical ripening and contractions. he benefit of prophylactic antibiotics in women with ruptured membranes before labor at term is


Obstentrics_Williams

Obstentrics_Williams. contraction, prostaglandin E1 (misoprostol) is chosen to promote cervical ripening and contractions. he benefit of prophylactic antibiotics in women with ruptured membranes before labor at term is unclear (Passos, 2012). However, in those with membranes ruptured longer than 18 hours, antibiotics are instituted for group B streptococcal infection prophylaxis (Chap. 64, p. 1221).


Obstentrics_Williams

Obstentrics_Williams. Labor can be too slow, but it also can be abnormally rapid. Precipitous labor and delivery is extremely rapid labor and delivery. It may result from an abnormally low resistance of the soft parts of the birth canal, from abnormally strong uterine and abdominal contractions, or rarely from the absence of painful sensations and thus a lack of awareness of vigorous labor. Precipitous labor terminates in expulsion of the fetus in less than 3 hours. Using this deinition, 25,260 live births-3 percent-were complicated by precipitous labor in the United States in 2013 (Martin, 2015). Despite this incidence, little published information describes maternal and perinatal outcomes.


Obstentrics_Williams

Obstentrics_Williams. For the mother, precipitous labor and delivery seldom are accompanied by serious maternal complications if the cervix is efaced appreciably and compliant, if the vagina has been stretched previously, and if the perineum is relaxed. Conversely, vigorous uterine contractions combined with a long, irm cervix and a noncompliant birth canal may lead to uterine rupture or extensive lacerations of the cervix, vagina, vulva, or perineum (Sheiner, 2004). It is in these latter circumstances that amnionic-luid embolism most likely develops (Chap. 41, p. 785). Precipitous labor is frequently followed by uterine atony. he uterus that contracts with unusual vigor bore delivery is likey to be hypotonic ater delivey. In one report of 99 term pregnancies, short labors were more common in multiparas who typically had contractions at intervals less than 2 minutes. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar


Obstentrics_Williams

Obstentrics_Williams. had contractions at intervals less than 2 minutes. Precipitous labors have been linked to cocaine abuse and associated with placental abruption, meconium, postpartum hemorrhage, and low Apgar scores (Mahon, 1994).


Obstentrics_Williams

Obstentrics_Williams. For the neonate, adverse perinatal outcomes from rapid labor may be increased considerably for several reasons. The tumultuous uterine contractions, often with negligible intervals of relaxation, prevent appropriate uterine blood flow and fetal oxygenation. Resistance of the birth canal may rarely cause intracranial trauma. Acker and coworkers (1988) reported that Erb or Duchenne brachial palsy was associated with such labors in a third of cases. Finally, during an unattended birth, the newborn may fall to the loor and be injured, or it may need resuscitation that is not immediately available.


Obstentrics_Williams

Obstentrics_Williams. As treatment, analgesia is unlikely to modiy these unusually forceful contractions to a signiicant degree. The use of tocolytic agents such as magnesium sulfate or terbutaline is unproven in these circumstances. Use of general anesthesia with agents that impair uterine contractibility such as isoflurane is often excessively heroic. Certainly, any oxytocin being administered should be stopped immediately. Fetopelvic disproportion arises from diminished pelvic capacity, from abnormal fetal size or presentation, or more usually from both. The pelvic inlet, midpelvis, or pelvic outlet may be contracted solely or in combination. Any contraction of the pelvic diameters that diminishes pelvic capacity can create dystocia during labor. Normal pelvic dimensions are additionally discussed and illustrated in Chapter 2 (p. 30).


Obstentrics_Williams

Obstentrics_Williams. Using clinical measures, it is important to identiy the shortest anteroposterior diameter through which the fetal head must pass. Before labor, the fetal biparietal diameter averages from 9.5 to as much as 9.8 cm. Therefore, it might prove diicult or even impossible for some fetuses to pass through a pelvic inlet that has an anteroposterior diameter < 10 cm. Mengert (1948) and Kaltreider (1952), employing x-ray pelvimetry, demonstrated that the incidence of diicult deliveries rises when either the anteroposterior diameter of the inlet is < 10 cm or the transverse diameter is < 12 cm. As expected, when both diameters are contracted, dystocia rates are much greater than when only one is contracted. Either of these measures is used to consider a pelvis contracted.


Obstentrics_Williams

Obstentrics_Williams. The anteroposterior diameter of the inlet, which is the obstetrical conjugate, is commonly approximated by manually measuring the diagonal conjugate, which is approximately 1.5 cm greater. Ascertainment of these measures is described in Chapter 2 (p. 30). Therefore, inlet contraction usually is defined as a diagonal conjugate < 11.5 cm. A small woman is likely to have a small pelvis, but she is also likely to have a small neonate. Thoms (1937) studied 362 nulliparas and found that the mean birth weight of their ofspring was significantly lower-280 g-in women with a small pelvis than in those with a medium or large pelvis.


Obstentrics_Williams

Obstentrics_Williams. Normally, cervical dilation is aided by hydrostatic action of the unruptured membranes or after their rupture, by direct application of the presenting part against the cervix. In con tracted pelves, however, because the head is arrested in the pelvic inlet, the entire force exerted by the uterus acts directly on the portion of membranes that contact the dilating cervix. Consequently, early spontaneous rupture of the membranes is more likely.


Obstentrics_Williams

Obstentrics_Williams. Consequently, early spontaneous rupture of the membranes is more likely. After membrane rupture, absent pressure by the head against the cervix and lower uterine segment predisposes to less efec tive contractions. Hence, further dilation may proceed very slowly or not at all. Cibils and Hendricks (1965) reported that the mechanical adaptation of the fetal passenger to the bony passage plays an important part in determining the eiciency of contractions. The better the adaptation, the more eicient the contractions. hus, cervical response to labor provides a prog nostic view of labor outcome in women with inlet contraction.


Obstentrics_Williams

Obstentrics_Williams. A contracted inlet also plays an important part in the pro duction of abnormal presentations. In nulliparas with normal pelvic capacity, the presenting part at term commonly descends into the pelvic cavity before labor onset. When the inlet is con tracted considerably or there is marked asynclitism, descent usually does not take place until after labor onset, if at all. Cephalic presentations still predominate, but the head loats freely over the pelvic inlet or rests more laterally in one of the iliac fossae. Accordingly, very slight influences may cause the fetus to assume other presentations. In women with contracted pelves, face and shoulder presentations are encountered three times more frequently, and the cord prolapses four to six times more often. his inding is more common than inlet contraction. It frequently causes transverse arrest of the fetal head, which potentially can lead to a diicult midforceps operation or to cesarean delivery.


Obstentrics_Williams

Obstentrics_Williams. his inding is more common than inlet contraction. It frequently causes transverse arrest of the fetal head, which potentially can lead to a diicult midforceps operation or to cesarean delivery. The obstetrical plane of the midpelvis extends from the inferior margin of the symphysis pubis through the ischial spines and touches the sacrum near the junction of the fourth and ifth vertebrae. A transverse line theoretically connecting the ischial spines divides the midpelvis into anterior and posterior portions (Fig. 2-16, p. 30). he former is bounded anteriorly by the lower border of the symphysis pubis and laterally by the ischiopubic rami. The posterior portion is bounded dorsally by the sacrum and laterally by the sacrospinous ligaments, forming the lower limits of the sacrosciatic notch.


Obstentrics_Williams

Obstentrics_Williams. Average midpelvis measurements are as follows: transverse, or interischial spinous, 10.5 cm; anteroposterior, from the lower border of the symphysis pubis to the junction of 54-5, 11.5 cm; and posterior sagittal, from the midpoint of the interspinous line to the same point on the sacrum, 5 cm. he deinition of midpelvic contractions has not been established with the same precision possible for inlet contractions. Even so, the midpelvis is likely contracted when the sum of the interspinous and posterior sagittal diameters of the midpelvis-normally, 10.5 plus 5 cm, or 15.5 cm-falls to 13.5 cm or less. his concept was emphasized by Chen and Huang (1982) in evaluating possible midpelvic contraction. Nlidpelvic contraction is suspected whenever the interspinous diameter is < 10 cm. When it mea sures < 8 cm, the midpelvis is contracted.


Obstentrics_Williams

Obstentrics_Williams. Although no precise manual method permits measure of midpelvic dimensions, a suggestion of contraction sometimes can be inferred if the spines are prominent, the pelvic sidewalls converge, or the sacrosciatic notch is narrow. Moreover, Eller and Mengert (1947) noted that the relationship between the intertuberous and interspinous diameters of the ischium is suf ficiently constant that narrowing of the interspinous diameter can be anticipated when the intertuberous diameter is narrow. A normal intertuberous diameter, however, does not always exclude a narrow interspinous diameter.


Obstentrics_Williams

Obstentrics_Williams. A normal intertuberous diameter, however, does not always exclude a narrow interspinous diameter. This inding usually is defined as an interischial tuberous diam eter of 8 cm or less. The pelvic outlet may be roughly likened to two triangles, with the interischial tuberous diameter con stituting the base of both. The sides of the anterior triangle are the pubic rami, and its apex is the inferoposterior surface of the symphysis pubis. The posterior triangle has no bony sides but is limited at its apex by the tip of the last sacral vertebra-not the tip of the coccyx. Diminution of the intertuberous diam eter with consequent narrowing of the anterior triangle must inevitably force the fetal head posteriorly. Floberg and asso almost 1 percent of more than 1400 unselected nulliparas with term pregnancies. A contracted outlet may cause dystocia not tion. Oulet contraction without concomitant midplane contrac tion is rare.


Obstentrics_Williams

Obstentrics_Williams. Although the disproportion between the fetal head and the pelvic outlet is not suiciently great to give rise to severe dystocia, it may play an important part in perineal tears. With increased narrowing of the pubic arch, the occiput cannot emerge directly beneath the symphysis pubis but is forced farther down upon the ischiopubic rami. The perineum, consequently, becomes increasingly distended and thus exposed to risk of laceration. Vallier (2012) reviewed experiences with pelvic fractures and pregnancy. Trauma from automobile collisions was the most common cause. Moreover, they note that fracture pattern, minor malalignment, and retained hardware are not absolute indications for cesarean delivery. In determining suitability for vaginal delivery, fracture healing requires 8 to 12 weeks and thus recent fracture merits cesarean delivery (Amorosa, 2013). A history of pelvic fracture warrants careful review of previous radiographs and possible imaging pelvimetry later in pregnancy.


Obstentrics_Williams

Obstentrics_Williams. The techniques for clinical evaluation using digital examination of the bony pelvis during labor are described in detail in Chapter 2 (p. 30). The value of radiological imaging to assess pelvic capacity has also been examined. First, with x-ray pelvimetry alone, the prognosis for successful vaginal delivery in any given pregnancy with cephalic presentation cannot be established (Mengert, 1948). Similarly, one systematic review found insufficient evidence to support the use of x-ray pelvimetry with cephalic presentations (Pattinson, 2017). Advantages of pelvimetry with computed tomography (CT) compared with those of conventional x-ray pelvimetry include greater accuracy and easier performance. With either method, costs are comparable, and x-ray exposure is small (Chap. 46, p. 906). Depending on the machine and technique employed, fetal doses with CT pelvimetry may range from 250 to 1500 mrad (Moore, 1989).


Obstentrics_Williams

Obstentrics_Williams. Advantages of magnetic resonance (MR) pelvimetry include lack of ionizing radiation, accurate measurements, complete fetal imaging, and the potential for evaluating soft tissue dystocia (McCarthy, 1986; Stark, 1985). Zaretsky and colleagues (2005) used l\1R imaging to measure pelvic and fetal head volume to identiy those women at greatest risk of undergoing cesarean delivery for dystocia. Signiicant associations were found between some of the measures and cesarean delivery for dystocia. However, these researchers could not with accuracy predict which individual woman would require cesarean delivery. Others have reported similar indings (Sporri, 1997).


Obstentrics_Williams

Obstentrics_Williams. Fetal size alone is seldom a suitable explanation for failed labor. Even with current technology, a fetal size threshold to predict fetopelvic disproportion is still elusive. Most cases of disproportion arise in fetuses whose weight is well within the range of the general obstetrical population. As shown in Figure 23-5, two thirds of neonates who required cesarean delivery after failed forceps delivery weighed <3700 g. hus, other factorsfor example, malposition of the head-obstruct fetal passage through the birth canal. hese include asynclitism, occiput posterior position, and face or brow presentation. For fetal head size estimation, clinical and radiographical methods to predict fetopelvic disproportion have proved �0 �O >� � x:5•x3 xO FIGURE 23-5 Birthweight distribution of 362 newborns born by cesarean delivery after a failed forceps attempt at Parkland Hospital from 1989-1•999. Only 12 percent (n 44) of the newborns weighed >4000 g (dark bars).


Obstentrics_Williams

Obstentrics_Williams. disappointing. Mueller (1885) and Hillis (1930) described a clinical maneuver to predict disproportion. The fetal brow and the suboccipital region are grasped through the abdominal wall with the fingers, and firm pressure is directed downward in the axis of the inlet. If no disproportion exists, the head readily enters the pelvis, and vaginal delivery can be predicted. Thorp and coworkers (1993) performed a prospective evaluation of this Mueler-Hillis maneuver. They found no relationship between failed descent during the maneuver and subsequent labor dystocia.


Obstentrics_Williams

Obstentrics_Williams. Measurements of fetal head diameters using plain radiographical techniques are not used because of parallax distortions. he biparietal diameter and head circumference can be measured sonographically, and investigators have attempted to use this information in the management of dystocia. hurnau and colleagues (1991) used the etal-pelvic index to identiy labor complications. Unfortunately, the sensitivity of such measurements to predict cephalopelvic disproportion is poor (Ferguson, 1998; Korhonen, 2015). We believe that no current method of measurement satisfactorily predicts fetopelvic disproportion based on head size.


Obstentrics_Williams

Obstentrics_Williams. With this presentation, the neck is hyperextended so that the occiput is in contact with the fetal back, and the chin (mentum) is presenting (Fig. 23-6). The fetal face may present with the chin (mentum) anteriorly or posteriorly, relative to the maternal symphysis pubis (Chap. 22, p. 425). Although some mentum posterior presentations persist, most convert spontaneously to anterior even in late labor (Duf, 1981). If not, the fetal brow (bregma) is pressed against the maternal symphysis pubis. his position precludes lexion of the fetal head necessary to negotiate the birth canal. hus, a mentum posterior presentation is undeliverable except with a very preterm fetus. FIGURE 23-6 Face presentation. The occiput is the longer end of the head lever. The chin is directly posterior. Vaginal delivery is impossible unless the chin rotates anteriorly. 450FIGURE 23-7 Mechanism of labor for right mentoposterior position with subsequent rotation of the mentum anteriorly and delivery.


Obstentrics_Williams

Obstentrics_Williams. 450FIGURE 23-7 Mechanism of labor for right mentoposterior position with subsequent rotation of the mentum anteriorly and delivery. Face presentation is diagnosed by vaginal examination and palpation of facial features. A breech may be mistaken for a face presentation. Namely, the anus may be mistaken for the mouth, and the ischial tuberosities for the malar prominences. Digital diferentiation is described in Chapter 28 (p. 540). Radiographically, demonstration of the hyperextended head with the facial bones at or below the pelvic inlet is characteristic. Cruikshank and White (1973) reported an incidence of 1 in 600, or 0.17 percent. As shown in Table 22-1 (p. 422), among more than 70,000 singleton newborns delivered at Parkland Hospital, approximately 1 in 2000 had a face presentation at delivery.


Obstentrics_Williams

Obstentrics_Williams. Causes of face presentations are numerous and include conditions that favor extension or prevent head lexion. Preterm fetuses, with their smaller head dimensions, can engage before conversion to vertex position (Shafer, 2006). In exceptional instances, marked enlargement of the neck or coils of cord around the neck may cause extension. Bashiri and associates (2008) reported that fetal malformations and hydramnios were risk factors for face or brow presentations. Anencephalic fetuses naturally present by the face. Extended neck positions develop more frequently when the pelvis is contracted or the fetus is very large. In a series of 141 face presentations studied by Hellman and coworkers (1950), the incidence of inlet contraction was 40 percent. his high incidence of pelvic contraction should be kept in mind when considering management.


Obstentrics_Williams

Obstentrics_Williams. High parity is a predisposing factor for face presentation (Fuchs, 1985). In these cases, a pendulous abdomen permits the back of the fetus to sag forward or laterally, often in the same direction in which the occiput points. his promotes extension of the cervical and thoracic spine. Mechanism of Labor


Obstentrics_Williams

Obstentrics_Williams. Mechanism of Labor Face presentations rarely are observed above the pelvic inlet. Instead, the brow generally presents early and is usually converted to present the face after further extension of the neck during descent. he mechanism of labor in these cases consists of the cardinal movements of descent, internal rotation, and flexion, and the accessory movements of extension and external rotation (Fig. 23-7). Descent is brought about by the same factors as in cephalic presentations. Extension results from the relation of the fetal body to the delected head, which is converted into a two-armed lever, the longer arm of which extends from the occipital condyles to the occiput. When resistance is encountered, the occiput must be pushed toward the back of the fetus while the chin descends.


Obstentrics_Williams

Obstentrics_Williams. The objective of internal rotation of the face is to bring the chin under the symphysis pubis. Only in this way can the neck traverse the posterior surface of the symphysis pubis. If the chin rotates directly posteriorly, the relatively short neck cannot span the anterior surface of the sacrum, which measures about 12 cm in length. Moreover, the fetal brow (bregma) is pressed against the maternal symphysis pubis. This position precludes lexion necessary to negotiate the birth canal. Hence, as discussed earlier, birth of the head from a mentum posterior position is impossible unless the shoulders enter the pelvis at the same time, an event that is impossible except when the fetus is extremely small or macerated. Internal rotation results from the same factors as in vertex presentations.


Obstentrics_Williams

Obstentrics_Williams. After anterior rotation and descent, the chin and mouth appear at the vulva, the undersurface of the chin presses against the symphysis, and the head is delivered by lexion. The nose, eyes, brow (bregma), and occiput then appear in succession over the anterior margin of the perineum. ter birth of the head, the occiput sags backward toward the anus. Next, the chin rotates externally to the side toward which it was originally directed, and the shoulders are born as in cephalic presentations. Edema may sometimes significantly distort the face. At the same time, the skull undergoes considerable molding, manifested by an increase in length of the occipitomental diameter of the head.


Obstentrics_Williams

Obstentrics_Williams. Edema may sometimes significantly distort the face. At the same time, the skull undergoes considerable molding, manifested by an increase in length of the occipitomental diameter of the head. In the absence of a contracted pelvis and with efective labor, successful vaginal delivery usually will follow. Fetal heart rate monitoring is probably better done with external devices to avoid damage to the face and eyes. Because face presentations among term-size fetuses are more common when there is some degree of pelvic inlet contraction, cesarean delivery frequently is indicated. Attempts to convert a face presentation manually into a vertex presentation, manual or forceps rotation of a persistently posterior chin to a mentum anterior position, and internal podalic version and extraction are dangerous and should not be attempted. Low or outlet forceps delivery of a mentum anterior face presentation can be completed and is described in Chapter 29 (p. 562).


Obstentrics_Williams

Obstentrics_Williams. This rare presentation is diagnosed when that portion of the fetal head between the orbital ridge and the anterior fontanel presents at the pelvic inlet. As shown in Figure 23-8, the fetal head thus occupies a position midway between full lexion (occiput) and extension (face). Except when the fetal head is small or the pelvis is unusually large, engagement of the fetal head and subsequent delivery cannot take place as long as the brow presentation persists. The causes of persistent brow presentation are the same as those for face presentation. A brow presentation is commonly unstable and often converts to a face or an occiput presentation (Cruikshank, 1973). The presentation may be recognized by abdominal palpation when both the occiput and chin can be palpated easily, but vaginal examination is usually necessary. The frontal sutures, large anterior fontanel, orbital ridges, eyes, and root of the nose are felt on vaginal examination, but neither the mouth nor the chin is palpable.


Obstentrics_Williams

Obstentrics_Williams. FIGURE 23-8 Brow posterior presentation. With a very small fetus and a large pelvis, labor is generally easy. With a larger fetus, it is usually diicult. his is because engagement is impossible until there is marked molding that shortens the occipitomental diameter or more commonly, until the neck either lexes to an occiput presentation or extends to a face presentation. The considerable molding essential for vaginal delivery of a persistent brow characteristically deforms the head. he caput succedaneum is over the forehead, and it may be so extensive that identiication of the brow by palpation is impossible. In these instances, the forehead is prominent and squared, and the occipitomental diameter is diminished. In transient brow presentations, the prognosis depends on the ultimate presentation. If the brow persists, prognosis is poor for vaginal delivery unless the fetus is small or the birth canal is large. Principles of management are the same as those for a face presentation.


Obstentrics_Williams

Obstentrics_Williams. In this position, the long axis of the fetus is approximately perpendicular to that of the mother. When the long axis forms an acute angle, an oblique lie results. The latter is usually only transitory, because either a longitudinal or transverse lie commonly results when labor supervenes. For this reason, the oblique lie is called an unstable lie in Great Britain. FIGURE 23-9 Leopold maneuver performed on a woman with a fetal transverse lie, right acromiodorsoanterior position. In a transverse lie, the shoulder is usually positioned over the pelvic inlet. The head occupies one iliac fossa, and the breech the other. This creates a shoulder presentation in which the side of the mother on which the acromion rests determines the designation of the lie as right or let acromial. And because in either position the back may be directed anteriorly or posteriorly, superiorly or inferiorly, it is customary to distinguish varieties as dorsoanterior and dorsoposterior (Fig. 23-9).


Obstentrics_Williams

Obstentrics_Williams. A transverse lie is usually recognized easily, often by inspection alone. The abdomen is unusually wide, whereas the uterine fundus extends to only slightly above the umbilicus. No fetal pole is detected in the fundus, and the ballottable head is found in one iliac fossa and the breech in the other. The position of the back is readily identifiable. When the back is anterior, a hard resistance plane extends across the front of the abdomen. When it is posterior, irregular nodulations representing fetal small parts are felt through the abdominal wall. On vaginal examination, in the early stages of labor, if the side of the thorax can be reached, it may be recognized by the "gridiron" feel of the ribs. With further dilation, the scapula and the clavicle are distinguished on opposite sides of the thorax. The position of the axilla indicates the side of the mother toward which the shoulder is directed.


Obstentrics_Williams

Obstentrics_Williams. (0.3 percent) at both the Mayo Clinic and the University of Iowa Hospital (Cruikshank, 1973; Johnson, 1964). This is remarkably similar to the incidence at Parkland Hospital of approximately 1 in 335 singleton fetuses. Some of the more common causes of transverse lie include: (1) abdominal wall relaxation from high parity, (2) preterm fetus, (3) placenta previa, (4) abnormal uterine anatomy, (5) hydramnios, and (6) contracted pelvis. Women with four or more deliveries have a tenfold incidence of transverse lie compared with nulliparas. A relaxed and pendulous abdomen allows the uterus to fall forward, delecting the long axis of the fetus away from the axis of the birth canal and into an oblique or transverse position. Placenta previa and pelvic contraction act similarly. A transverse or oblique lie occasionally develops in labor from an initial longitudinal position. Mechanism of Labor


Obstentrics_Williams

Obstentrics_Williams. Mechanism of Labor Spontaneous delivery of a fully developed newborn is impossible with a persistent transverse lie. After rupture of the membranes, if labor continues, the fetal shoulder is forced into the pelvis, and the corresponding arm frequently prolapses (Fig. 23-10). After some descent, the shoulder is arrested by the margins of the pelvic inlet. As labor continues, the shoulder is impacted irmly in the upper part of the pelvis. he uterus then contracts vigorously in an unsuccessful attempt to overcome the obstacle. With time, a retraction ring rises increasingly higher and becomes more marked. With this neglected transverse lie, the uterus will eventually rupture. Even without this complication, morbidity is increased because of the frequent association


Obstentrics_Williams

Obstentrics_Williams. FIGURE 23-10 Neglected shoulder presentation. A thick cular band forming a pathological retraction ring has developed just above the thin lower uterine segment. The force generated during a uterine contraction is directed centripetally at and above the level of the pathological retraction ring. This serves to stretch further and possibly to rupture the thin lower segment below the retraction ring. with placenta previa, the increased likelihood of cord prolapse, and the necessity for major operative eforts.


Obstentrics_Williams

Obstentrics_Williams. with placenta previa, the increased likelihood of cord prolapse, and the necessity for major operative eforts. If the fetus is small-usually < 800 g-and the pelvis is large, spontaneous delivery is possible despite persistence of the abnormal lie. The fetus is compressed with the head forced against its abdomen. A portion of the thoracic wall below the shoulder thus becomes the most dependent part, appearing at the vulva. he head and thorax then pass through the pelvic cavity at the same time. he fetus, which is doubled upon itself and thus sometimes referred to as condupLicato corpore, is expelled.


Obstentrics_Williams

Obstentrics_Williams. Active labor in a woman with a transverse lie is usually an indication for cesarean delivery. Before labor or early in labor, with the membranes intact, attempts at external version are worthwhile in the absence of other complications. If the fetal head can be maneuvered by abdominal manipulation into the pelvis, it should be held there during the next several contractions in an attempt to ix the head in the pelvis. With cesarean delivery, because neither the feet nor the head of the fetus occupies the lower uterine segment, a low transverse incision into the uterus may lead to diicult fetal extraction. his is especially true of dorsoanterior presentations. herefore, a vertical hysterotomy incision is often indicated .


Obstentrics_Williams

Obstentrics_Williams. With this, an extremity prolapses alongside the presenting part, and both present simultaneously in the pelvis (Fig. 23-11). Goplerud and Eastman (1953) identiied a hand or arm prolapsed alongside the head once in every 700 deliveries. Much less common was prolapse of one or both lower extremities alongside a cephalic presentation or a hand alongside a breech. At Parkland Hospital, compound presentations were identiied in only 68 of more than 70,000 singleton fetuses-an incidence of approximately 1 in 1000. Causes of compound presentations are conditions that prevent complete occlusion of the pelvic inlet by the fetal head, including preterm labor.


Obstentrics_Williams

Obstentrics_Williams. In most cases, the prolapsed part should be left alone, because most often it will not interfere with labor. If the arm is prolapsed alongside the head, the condition should be observed closely to ascertain whether the arm retracts out of the way with descent of the presenting part. If it fails to retract and if it appears to prevent descent of the head, the prolapsed arm should be pushed gently upward and the head simultaneously downward by fundal pressure. In general, rates of perinatal mortality and morbidity are increased as a result of concomitant preterm delivery, prolapsed cord, and traumatic obstetrical procedures. Serious injury to the forearm is rare (Kwok, 2015; Tebes, 1999). Dystocia, especially if labor is prolonged, is associated with a higher incidence of several common obstetrical and neonatal complications. Inection, either intrapartum chorioamnionitis or postpartum pelvic infection, is more common with desultory


Obstentrics_Williams

Obstentrics_Williams. FIGURE 23-11 Compound presentation. A. The left hand is lying in front of the vertex. With further labor, the hand and arm may retract from the birth canal, and the head may then descend normally. B. Photograph of a small 34-week fetus with a compound presentation that delivered uneventfully with the hand presenting first. (Used with permission from Dr. Elizabeth Mosier.) and prolonged labors. Pospartum hemorrhage rates from atony are increased with prolonged and augmented labors. Uterine tears with hysterotomy also occur at greater incidence if the fetal head is impacted in the pelvis.


Obstentrics_Williams

Obstentrics_Williams. Uterine rupture is another risk. Abnormal thinning of the lower uterine segment creates a serious danger during prolonged labor, particularly in women of high parity and in those with a prior cesarean delivery. When disproportion is so pronounced that there is no engagement or descent, the lower uterine segment becomes increasingly stretched, and rupture may follow. In such cases, the normal contraction ring is usually exaggerated, like that shown in Figure 23-10.


Obstentrics_Williams

Obstentrics_Williams. Such pathological retraction rings are localized constrictions of the uterus that develop in association with prolonged obstructed labors. Seldom encountered today, the pathological retraction ring o/Bandl is associated with marked stretching and thinning of the lower uterine segment. In contemporary practice, after birth of a irst twin, a pathological ring may still develop occasionally as an hourglass constriction of the uterus. he band may be seen clearly as a uterine indentation and signifies impending rupture of the lower uterine segment. he ring can sometimes be relaxed and delivery efected with appropriate general anesthesia, but for the second twin (Chap. 45, p. 890).


Obstentrics_Williams

Obstentrics_Williams. Fistula ormation may result from dystocia, as the presenting part is irmly wedged into the pelvic inlet. Tissues of the birth canal lying between the leading part and the pelvic wall may be subjected to excessive pressure. Because of impaired circula tion, necrosis can result and become evident several days after delivery as vesicovaginal, vesicocervical, or rectovaginal istulas. Most often, pressure necrosis follows a very prolonged second stage. Such fistulas are rarely seen today except in undeveloped countries.


Obstentrics_Williams

Obstentrics_Williams. Most often, pressure necrosis follows a very prolonged second stage. Such fistulas are rarely seen today except in undeveloped countries. recent attention. The pelvic floor is exposed to direct compres sion from the fetal head and to downward pressure from mater nal expulsive eforts. These forces stretch and distend the pelvic floor, resulting in functional and anatomical alterations in the muscles, nerves, and connective tissues. Accumulating evidence suggests that such efects on the pelvic floor during childbirth can afect urinary or anal continence and pelvic support. hese relationships are discussed in Chapter 30 (p. 568).


Obstentrics_Williams

Obstentrics_Williams. Lower extremiy nerve injuy in the mother can follow prolonged second-stage labor. Wong and colleagues (2003) reviewed neurological injury involving the lower extremities in association with labor and delivery. The most common mechanism is external compression of the common fibular (formerly common peroneal) nerve. This is usually caused by inappropriate leg positioning in stirrups, especially during prolonged second-stage labor. hese and other injuries are discussed in Chapter 36 (p. 661). Fortunately, symptoms resolve within 6 months of delivery in most women. Similar to the mother, the incidence of peripartum fetal sepsis rises with longer labors. Caput succedaneum and molding develop commonly and may be impressive (Fig. 22-16, p. 431) (Buchmann, 2008). Mechanical trauma such as nerve injury, fractures, and cephalohematoma are also more frequent and are discussed further in Chapter 33 (p. 627). Acker DB, Gregory KD, Sachs BP, et al: Risk factors for Erb-Duchenne palsy.


Obstentrics_Williams

Obstentrics_Williams. Acker DB, Gregory KD, Sachs BP, et al: Risk factors for Erb-Duchenne palsy. Obstet Gynecol 71:389, 1988 Alexander J: MFMU Cesarean Registry: labor characteristics of women undergo ing cesarean delivery for dystocia. Am J Obstet Gynecol 189(6):5138,2003 Allen VM, Baskett TF, O'Connell CM, et al: Maternal and perinatal outcomes with increasing duration of the second stage oflabor. Obstet Gynecol 113(6):1248,r2009 American College of Obstetricians and Gynecologists, Society for Matenal Fetal Medicine: Safe prevention of the primary cesarean delivery. Obstetric Care Consensus No.r1, March 2014, Reairmed 2016 Amorosa LF, Amorosa JH, Wellman OS, et al: Management of pelvic injuries in pregnancy. Orthop Clin North Am 44(3):301,r2013 Bashiri A, Burstein E, Bar-David J, et al: Face and brow presentation: independent risk factors. ] Matern Fetal Neonatal Med 21 (6):357, 2008


Obstentrics_Williams

Obstentrics_Williams. Bashiri A, Burstein E, Bar-David J, et al: Face and brow presentation: independent risk factors. ] Matern Fetal Neonatal Med 21 (6):357, 2008 Bleich AT, Alexander ]M, McIntire DO, et al: An analysis of second-stage labor beyond 3 hours in nulliparous women. Am] PerinatoI29:717, 2012 Buchmann E], Libhaber E: Sagittal suture overlap in cephalopelvic disproportion: blinded and non-participant assessment. Acta Obstet Gynecol Scand 87(7):731,r2008 Caldeyro-Barcia R, Alvarez H, Reynolds SR: A better understanding of uterine contractility through simultaneous recording with an internal and a seven channel external method. Surg Obstet Gynecol 91:641, 1950 Chen HY, Huang SC: Evaluation of midpelvic contraction. Int Surg 67:516, 1982 Cheng YW, Hopkins LM, Caughey AB: How long is too long: does a prolonged second stage oflabor in nulliparous women afect matenal and neonatal outcomes? Am] Obstet GynecoIr191(3):933, 2004


Obstentrics_Williams

Obstentrics_Williams. Cheng YW, Hopkins LM, Caughey AB: How long is too long: does a prolonged second stage oflabor in nulliparous women afect matenal and neonatal outcomes? Am] Obstet GynecoIr191(3):933, 2004 Cheng YW, Shafer BL, Bryant AS, et al: Length of the irst stage of labor and associated perinatal outcomes in nulliparous women. Obstet Gynecol 116(5):1127,r2010 Cibils LA, Hendricks CH: Normal labor in vertex presentation. Am J Obstet GynecoIr91:385, 1965 Cohen W: InAuence of the duration of second stage labor on perinatal outcome and puerperal morbidity. Obstet Gynecol 49:266, 1977 Cohen W, Friedman EA: Management of Labor. Baltimore, University Park Press, 1983 Cohen WR, Friedman EA: Misguided guidelines for managing labor. Am J Obstet Gynecol 212(6):753.el, 2015a Cohen WR, Friedman EA: Perils of the new labor management guidelines. Am J Obstet Gynecol 212(4):420, 2015b Cruikshank DP, White CA: Obstetric malpresentations: twenty years' experience. Am J Obstet Gynecol 116:1097, 1973


Obstentrics_Williams

Obstentrics_Williams. Cruikshank DP, White CA: Obstetric malpresentations: twenty years' experience. Am J Obstet Gynecol 116:1097, 1973 Duf P: Diagnosis and management of face presentation. Obstet Gynecol 57:105,r1981 Eller We, Mengert WF: Recognition of mid-pelvic contraction. Am ] Obstet Gynecol 53:252, 1947 Ferguson ]E, Newberry YG, DeAngelis GA, et al: he fetal-pelvic index has minimal utility in predicting fetal-pelvic disproportion. Am J Obstet Gynecol 179: 1186, 1998 Floberg], Belfrage P, Ohlsen H: InAuence of pelvic outlet capacity on labor. A prospective pelvimetry study of 1,429 unselected primiparas. Acta Obstet Gynecol Scand 66: 121, 1987 Fraser WD, Marcoux 5, Krauss I, et al: Multicenter, randomized, controlled trial of delayed pushing for nulliparous women in the second stage of labor with continuous epidural analgesia. Am J Obstet Gynecol 182: 1165,r2000


Obstentrics_Williams

Obstentrics_Williams. Friedman E: The graphic analysis of labor. Am] Obstet Gynecol68: 1568, 1954 Friedman EA: Labor. Clinical Evaluation and Management, 2nd ed. New York, Appleton-Century-Crofts, Friedman EA: Primigravid labor; a graphicostatistical analysis. Obstet Gynecol 6(6):567, 1955 Friedman EA, Sachtleben MR: Station of the fetal presenting part 11: effect on the course oflabor. Am] Obstet Gynecol 93:530, 1965 Friedman EA, Sachtleben MR: Station of the fetal presenting part IV: arrest of descent in nulliparas. Obstet :129,r1976 Fuchs K, Peretz BA, Marcovici R, et al: The grand multipara-is it a problem? Int J Gynaecol Obstet 73:321, 1985 Gambling DR, Sharma SK, Ramin SM, et al: A randomized study of combined spinal-epidural analgesia versus intravenous meperidine during labor: impact on cesarean delivery rate. Anesthesiology 89(6): 1336, 1998 Goplerud ], Eastman N]: Compound presentation: survey of 65 cases. Obstet Gynecol 1:59, 1953