Polyhydramnios (also known as hydramnios) refers to an excessive volume of amniotic fluid. It has been associated with an increased risk of various adverse pregnancy outcomes, including preterm birth, placental abruption, and fetal anomalies [1-3]. Polyhydramnios should be suspected clinically when uterine size is large for gestational age. The diagnosis is made prenatally by ultrasound examination using a noninvasive qualitative or quantitative approach. (See "Assessment of amniotic fluid volume".)


The incidence of polyhydramnios in a general obstetric population generally ranges from 1 to 2 percent [4-8]. Reported rates are influenced by variations in diagnostic criteria, the population studied (low or high risk), the subjective volume of fluid where polyhydramnios is diagnosed (eg, mild, moderate, or severe), and the gestational age (preterm, term, or postterm) at examination. In one series of 93,332 singleton pregnancies delivering at a single hospital from 1991 to 1997, polyhydramnios was diagnosed during antepartum sonography in 708 pregnancies (0.7 percent of deliveries); mild, moderate, and severe disease occurred in 66, 22, and 12 percent of cases, respectively [5].


The volume of amniotic fluid reflects the balance between fluid production and movement of fluid out of the amniotic sac; the regulation of this process is incompletely understood. (See "Physiology of amniotic fluid volume regulation".) In late gestation, the primary sources of amniotic fluid production are fetal urination and secretion of lung fluid; oral and nasal secretions make minimal contributions. The main routes of amniotic fluid removal are fetal swallowing and absorption via the intramembranous pathway. Even a relatively minor increase in daily fetal urine production or decrease in fetal swallowing can result in a marked increase in amniotic fluid volume (AFV) [9-11].


The most common cause of severe polyhydramnios are fetal anomalies (often associated with an underlying genetic diagnosis), while maternal diabetes, multiple gestation, and idiopathic factors are more often associated with milder cases. In one series of 272 singleton pregnancies with polyhydramnios, approximately one-third were associated with a congenital anomaly and one-quarter were associated with maternal diabetes; the remaining 40 percent were considered idiopathic [12]. After birth, an abnormality is diagnosed in up to 25 percent of cases considered idiopathic prenatally [12-15]. Fetal infection, Bartter syndrome, anemia, and neuromuscular disorders account for some of these cases and should be considered in the differential diagnosis if a structural abnormality and maternal diabetes are excluded, although Bartter syndrome and neuromuscular diseases are quite rare.

Polyhydramnios has been associated with fetal anomalies in most organ systems. The most common structural anomalies associated with polyhydramnios are those that interfere with fetal swallowing and/or absorption of fluid [16,17]. Decreased swallowing may be due to a primary gastrointestinal obstruction (eg, duodenal, esophageal, or intestinal atresia), neuromuscular disorders (eg, anencephaly), or to secondary obstruction of the gastrointestinal tract (eg, massive unilateral dysplastic kidneys).


Subscribers log in here

Literature review current through: Jun 2014. | This topic last updated: May 2, 2014.
  1. Golan A, Wolman I, Sagi J, et al. Persistence of polyhydramnios during pregnancy--its significance and correlation with maternal and fetal complications. Gynecol Obstet Invest 1994; 37:18.
  2. Many A, Hill LM, Lazebnik N, Martin JG. The association between polyhydramnios and preterm delivery. Obstet Gynecol 1995; 86:389.
  3. Smith CV, Plambeck RD, Rayburn WF, Albaugh KJ. Relation of mild idiopathic polyhydramnios to perinatal outcome. Obstet Gynecol 1992; 79:387.
  4. Hill LM, Breckle R, Thomas ML, Fries JK. Polyhydramnios: ultrasonically detected prevalence and neonatal outcome. Obstet Gynecol 1987; 69:21.
  5. Dashe JS, McIntire DD, Ramus RM, et al. Hydramnios: anomaly prevalence and sonographic detection. Obstet Gynecol 2002; 100:134.
  6. Thompson O, Brown R, Gunnarson G, Harrington K. Prevalence of polyhydramnios in the third trimester in a population screened by first and second trimester ultrasonography. J Perinat Med 1998; 26:371.
  7. Biggio JR Jr, Wenstrom KD, Dubard MB, Cliver SP. Hydramnios prediction of adverse perinatal outcome. Obstet Gynecol 1999; 94:773.
  8. Pri-Paz S, Khalek N, Fuchs KM, Simpson LL. Maximal amniotic fluid index as a prognostic factor in pregnancies complicated by polyhydramnios. Ultrasound Obstet Gynecol 2012; 39:648.
  9. Harding R, Bocking AD, Sigger JN, Wickham PJ. Composition and volume of fluid swallowed by fetal sheep. Q J Exp Physiol 1984; 69:487.
  11. Pritchard JA. Fetal swallowing and amniotic fluid volume. Obstet Gynecol 1966; 28:606.
  12. Abele H, Starz S, Hoopmann M, et al. Idiopathic polyhydramnios and postnatal abnormalities. Fetal Diagn Ther 2012; 32:251.
  13. Dorleijn DM, Cohen-Overbeek TE, Groenendaal F, et al. Idiopathic polyhydramnios and postnatal findings. J Matern Fetal Neonatal Med 2009; 22:315.
  14. Touboul C, Boileau P, Picone O, et al. Outcome of children born out of pregnancies complicated by unexplained polyhydramnios. BJOG 2007; 114:489.
  15. Touboul C, Picone O, Levaillant JM, et al. Clinical application of fetal urine production rate in unexplained polyhydramnios. Ultrasound Obstet Gynecol 2009; 34:521.
  16. Ben-Chetrit A, Hochner-Celnikier D, Ron M, Yagel S. Hydramnios in the third trimester of pregnancy: a change in the distribution of accompanying fetal anomalies as a result of early ultrasonographic prenatal diagnosis. Am J Obstet Gynecol 1990; 162:1344.
  17. Stoll CG, Alembik Y, Dott B. Study of 156 cases of polyhydramnios and congenital malformations in a series of 118,265 consecutive births. Am J Obstet Gynecol 1991; 165:586.
  18. Sieck UV, Ohlsson A. Fetal polyuria and hydramnios associated with Bartter's syndrome. Obstet Gynecol 1984; 63:22S.
  19. Vink JY, Poggi SH, Ghidini A, Spong CY. Amniotic fluid index and birth weight: is there a relationship in diabetics with poor glycemic control? Am J Obstet Gynecol 2006; 195:848.
  20. Idris N, Wong SF, Thomae M, et al. Influence of polyhydramnios on perinatal outcome in pregestational diabetic pregnancies. Ultrasound Obstet Gynecol 2010; 36:338.
  21. Ross MG, Brace RA, National Institute of Child Health and Development Workshop Participants. National Institute of Child Health and Development Conference summary: amniotic fluid biology--basic and clinical aspects. J Matern Fetal Med 2001; 10:2.
  22. Magann EF, Chauhan SP, Doherty DA, et al. A review of idiopathic hydramnios and pregnancy outcomes. Obstet Gynecol Surv 2007; 62:795.
  23. Erez O, Shoham-Vardi I, Sheiner E, et al. Hydramnios and small for gestational age are independent risk factors for neonatal mortality and maternal morbidity. Arch Gynecol Obstet 2005; 271:296.
  24. Sickler GK, Nyberg DA, Sohaey R, Luthy DA. Polyhydramnios and fetal intrauterine growth restriction: ominous combination. J Ultrasound Med 1997; 16:609.
  25. Maymon E, Ghezzi F, Shoham-Vardi I, et al. Isolated hydramnios at term gestation and the occurrence of peripartum complications. Eur J Obstet Gynecol Reprod Biol 1998; 77:157.
  26. Mazor M, Ghezzi F, Maymon E, et al. Polyhydramnios is an independent risk factor for perinatal mortality and intrapartum morbidity in preterm delivery. Eur J Obstet Gynecol Reprod Biol 1996; 70:41.
  27. Panting-Kemp A, Nguyen T, Chang E, et al. Idiopathic polyhydramnios and perinatal outcome. Am J Obstet Gynecol 1999; 181:1079.
  29. Brace RA. Progress toward understanding the regulation of amniotic fluid volume: water and solute fluxes in and through the fetal membranes. Placenta 1995; 16:1.
  30. Magann EF, Chauhan SP, Barrilleaux PS, et al. Amniotic fluid index and single deepest pocket: weak indicators of abnormal amniotic volumes. Obstet Gynecol 2000; 96:737.
  31. Barnhard Y, Bar-Hava I, Divon MY. Is polyhydramnios in an ultrasonographically normal fetus an indication for genetic evaluation? Am J Obstet Gynecol 1995; 173:1523.
  33. Lee SM, Jun JK, Lee EJ, et al. Measurement of fetal urine production to differentiate causes of increased amniotic fluid volume. Ultrasound Obstet Gynecol 2010; 36:191.
  34. Fayyaz H, Rafi J. TORCH screening in polyhydramnios: an observational study. J Matern Fetal Neonatal Med 2012; 25:1069.
  35. Elliott JP, Sawyer AT, Radin TG, Strong RE. Large-volume therapeutic amniocentesis in the treatment of hydramnios. Obstet Gynecol 1994; 84:1025.
  36. Cabrol D, Landesman R, Muller J, et al. Treatment of polyhydramnios with prostaglandin synthetase inhibitor (indomethacin). Am J Obstet Gynecol 1987; 157:422.
  37. Hickok DE, Hollenbach KA, Reilley SF, Nyberg DA. The association between decreased amniotic fluid volume and treatment with nonsteroidal anti-inflammatory agents for preterm labor. Am J Obstet Gynecol 1989; 160:1525.
  38. Kirshon B, Mari G, Moise KJ Jr. Indomethacin therapy in the treatment of symptomatic polyhydramnios. Obstet Gynecol 1990; 75:202.
  39. Rode L, Bundgaard A, Skibsted L, et al. Acute recurrent polyhydramnios: a combination of amniocenteses and NSAID may be curative rather than palliative. Fetal Diagn Ther 2007; 22:186.
  40. Fisk NM, Tannirandorn Y, Nicolini U, et al. Amniotic pressure in disorders of amniotic fluid volume. Obstet Gynecol 1990; 76:210.
  41. Leung WC, Jouannic JM, Hyett J, et al. Procedure-related complications of rapid amniodrainage in the treatment of polyhydramnios. Ultrasound Obstet Gynecol 2004; 23:154.
  42. Jauniaux E, Holmes A, Hyett J, et al. Rapid and radical amniodrainage in the treatment of severe twin-twin transfusion syndrome. Prenat Diagn 2001; 21:471.
  43. Kramer WB, Van den Veyver IB, Kirshon B. Treatment of polyhydramnios with indomethacin. Clin Perinatol 1994; 21:615.
  44. Harman CR. Amniotic fluid abnormalities. Semin Perinatol 2008; 32:288.
  45. Moise KJ Jr. Polyhydramnios. Clin Obstet Gynecol 1997; 40:266.
  46. Bartfield M, Carlan SJ. The safety and efficacy of prolonged outpatient sulindac to prevent the recurrence of preterm labor: a prospective double-blind study. Prim Care Update Ob Gyns 1998; 5:178.
  47. Kramer WB, Saade GR, Belfort M, et al. A randomized double-blind study comparing the fetal effects of sulindac to terbutaline during the management of preterm labor. Am J Obstet Gynecol 1999; 180:396.
  48. Peek MJ, McCarthy A, Kyle P, et al. Medical amnioreduction with sulindac to reduce cord complications in monoamniotic twins. Am J Obstet Gynecol 1997; 176:334.
  49. Gilbert WM, Cheung CY, Brace RA. Rapid intramembranous absorption into the fetal circulation of arginine vasopressin injected intraamniotically. Am J Obstet Gynecol 1991; 164:1013.
  50. Kullama LK, Nijland MJ, Ervin MG, Ross MG. Intraamniotic deamino(D-Arg8)-vasopressin: prolonged effects on ovine fetal urine flow and swallowing. Am J Obstet Gynecol 1996; 174:78.
  51. Mann SE, Dvorak N, Gilbert H, Taylor RN. Steady-state levels of aquaporin 1 mRNA expression are increased in idiopathic polyhydramnios. Am J Obstet Gynecol 2006; 194:884.
  52. Zhu X, Jiang S, Hu Y, et al. The expression of aquaporin 8 and aquaporin 9 in fetal membranes and placenta in term pregnancies complicated by idiopathic polyhydramnios. Early Hum Dev 2010; 86:657.
  53. Kramer MS, Rouleau J, Baskett TF, et al. Amniotic-fluid embolism and medical induction of labour: a retrospective, population-based cohort study. Lancet 2006; 368:1444.