Management of Symptomatic Polyhydramnios
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Polyhydramnios (or hydramnios) is an excessive amount of amniotic fluid relative to gestational age. It is thought to result from either increased production or decreased clearance of amniotic fluid and is often suspected when uterine size is greater than dates. Polyhydramnios may be initially identified sonographically or through subjective impression. Quantified measurements include the amniotic fluid index (AFI) and deepest vertical pocket (DVP). It is characterized as mild (AFI 24.0-29.9 cm or DVP ≥ 8 and < 12 cm), moderate (AFI 30.0-34.9 cm or DVP ≥12 and < 16 cm), or severe (AFI ≥ 35.0cm or DVP ≥16cm).
The etiologies of polyhydramnios are most often idiopathic (50-60%), or related to maternal diabetes (20%), fetal malformations (10-15%), fetal infections, multiple gestations (5-10%), or isoimmunization (1%). Polyhydramnios is associated with increased risk of preterm premature rupture of membranes, preterm birth, macrosomia, malpresentation, umbilical cord prolapse, abruption, stillbirth, uterine atony and postpartum hemorrhage, and other adverse outcomes. These complications increase the risk of cesarean delivery and NICU admission. The uterine distension found in severe polyhydramnios can be associated with maternal symptoms including shortness of breath with respiratory compromise, uterine irritability and contractions, and abdominal discomfort.
Recommendations for evaluation and management are similar for both singleton and twin gestations. Evaluation includes a comprehensive ultrasound to assess for anomalies and hydrops. Other testing should include diabetes and alloantibody screening, rapid plasma reagin (RPR), parvovirus, toxoplasmosis, and cytomegalovirus (CMV) testing when indicated. Genetic evaluation may be considered to evaluate for aneuploidy, especially when polyhydramnios is severe, is diagnosed prior to 24 weeks, or when coexisting fetal anomalies or fetal growth restriction are identified.
For severe polyhydramnios, antenatal testing should be considered at 32-34 weeks gestation along with serial ultrasound evaluation to monitor amniotic fluid levels and fetal growth. Use of prostaglandin synthetase inhibitor (e.g., indomethacin) is no longer recommended because of insufficient evidence of efficacy in improving maternal outcomes and increased risks of adverse neonatal outcomes. Given the risk of preterm birth, consideration should be given to the administration of antenatal corticosteroids.
In cases of severe or symptomatic polyhydramnios, amnioreduction may be performed. No consensus exists on the speed or volume of amniotic fluid removal. There is no consensus on the roles of tocolytics and antibiotics. Complications of amnioreduction occur relatively infrequently (1-3%) and include rupture of membranes, preterm labor, placental abruption, infection, and hypoproteinemia.
Delivery is recommended no later than 39-40 weeks. Severe and symptomatic situations require balancing the risks of early delivery against the risks of the interventions. Polyhydramnios is not itself an indication for cesarean delivery. Artificial membrane rupture should be delayed, avoided, or performed carefully with consideration of controlled amniotomy using a small gauge needle to avoid complications such as cord prolapse and abruption. Fetal presentation should be monitored during labor and providers should be prepared for increased likelihood of postpartum hemorrhage.
Society for Maternal-Fetal Medicine (SMFM). Electronic address: email@example.com, Dashe JS, Pressman EK, Hibbard JU. SMFM Consult Series #46: Evaluation and management of polyhydramnios. Am J Obstet Gynecol. 2018 Oct;219(4):B2-B8. doi: 10.1016/j.ajog.2018.07.016. Epub 2018 Jul 23. PMID: 30048635.
Committee on Practice Bulletins—Obstetrics and the American Institute of Ultrasound in Medicine. Practice Bulletin No. 175: Ultrasound in Pregnancy. Obstet Gynecol. 2016 Dec;128(6):e241-e256.
Initial approval September 2016, Reaffirmed March 2018, Reaffirmed September 2019, Revised May 2021; Revised November 2022.
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