Polyhydramnios

Polyhydramnios is an amniotic fluid volume that is greater than expected for gestational age. Causes may be idiopathic (in approx. 70% of cases) or due to maternal (e.g., diabetes, rhesus incompatibility) or fetal factors (e.g., conditions that impair swallowing or increase urine production). Polyhydramnios is often discovered incidentally on routine prenatal ultrasound or during an evaluation for increased fundal height for gestational age. All patients should be referred to maternal-fetal medicine for further evaluation and management of underlying causes and/or complications. Idiopathic, uncomplicated, mild polyhydramnios is managed with routine care and delivery at term. Additional management (e.g., antepartum fetal surveillance, planned delivery at a tertiary care center, and/or amnioreduction) is individualized based on identified causes, complications, and disease severity. Complications include intrauterine fetal demise, fetal malposition, umbilical cord prolapse, premature labor and birth, and complications due to underlying fetal factors.

Polyhydramnios is idiopathic in ∼ 70% of cases but may also occur due to underlying fetal or maternal factors.

Fetal factors ^[1][2]

• Impaired swallowing
  • Gastrointestinal obstructions (e.g., tracheoesophageal fistula, esophageal atresia, duodenal atresia)
  • Esophageal compression (e.g., from congenital neck masses or congenital pulmonary airway malformations) ^[3]
  • Neuromuscular disorders (e.g., neural tube defects, myotonic dystrophy)
  • Craniofacial deformities (e.g., cleft lip, cleft palate, micrognathia)
• Increased urine production
  • High-output cardiac states (e.g., tachyarrhythmias, fetal anemia)
  • Inability to concentrate urine (e.g., Bartter syndrome, diabetes insipidus)
  • Twin-to-twin transfusion syndrome (recipient twin) ^[4][5]
• Other
  • Chromosomal abnormalities (e.g., aneuploidy)
  • TORCH infections

Maternal factors ^[1][2]

• Diabetes mellitus
• Rhesus incompatibility

Polyhydramnios is diagnosed with an obstetric ultrasound, typically in the 2^nd or 3^rd trimester. ^[1][6]

• Indications
  • Routine prenatal care or antepartum fetal surveillance
  • Fundal height increased for gestational age ^[1]
• Findings ^[1][7]
  • Increased amniotic fluid determined by either of the following:
    • Deepest vertical pocket (DVP): ≥ 8 cm ^[1]
    • Amniotic fluid index (AFI): ≥ 24 cm
  • Severity of polyhydramnios ^[1]
    • Mild polyhydramnios: AFI 24–29.9 cm or DVP 8–11 cm
    • Moderate polyhydramnios: AFI 30–35 cm or DVP 12–15 cm
    • Severe polyhydramnios: AFI > 35 cm or DVP ≥ 16 cm
  • Fetal abnormalities associated with polyhydramnios

Routine prenatal care includes screening for diabetes, alloimmunization, and syphilis. ^[1]

Refer patients with polyhydramnios to maternal-fetal medicine for further evaluation and management, which may include the following: ^[1][8]

• Evaluation for causes of polyhydramnios and fetal complications of polyhydramnios
  • Detailed fetal ultrasound
  • Screen for maternal diabetes (or rescreen if prior testing was normal)
  • Optimization of modifiable conditions (e.g., management of diabetes in pregnancy, management of maternal alloimmunization)
• Prenatal care and delivery planning
  • Idiopathic, uncomplicated, mild polyhydramnios ^[1]
    • Routine prenatal care
    • Spontaneous delivery at term (i.e., ≥ 39 weeks' gestation)
  • Underlying cause, complication, and/or moderate to severe polyhydramnios ^[7]
    • Antepartum fetal surveillance ^[7]
    • Planned delivery at a tertiary care center ^[1]
• Amnioreduction (drainage of excess amniotic fluid) for temporary symptomatic relief. ^[9]
  • Indications: severe polyhydramnios causing severe maternal discomfort and/or dyspnea ^[7]
  • Complications: preterm labor or premature rupture of membranes

Management is individualized based on the severity of polyhydramnios, underlying cause, and any associated complications. ^[1]

• Fetal complications
  • Intrauterine fetal demise ^[7]
  • Intrauterine growth restriction ^[1]
  • Macrosomia ^[2]
• Delivery complications ^[1]
  • Fetal malposition
  • Umbilical cord prolapse
  • Preterm labor and birth
  • Premature rupture of membranes
  • Obstetric interventions (e.g., assisted vaginal delivery, cesarean delivery)

We list the most important complications. The selection is not exhaustive.