How is polyhydramnios diagnosed and managed?

Diagnosis and Management of Polyhydramnios

Polyhydramnios should be diagnosed using ultrasound with specific measurement criteria and managed based on severity, underlying etiology, and maternal symptoms, with interventions reserved primarily for severe symptomatic cases. 1

Diagnostic Criteria

Polyhydramnios is defined as an abnormal increase in amniotic fluid volume, diagnosed by ultrasound using either:

• Deepest Vertical Pocket (DVP) ≥8 cm OR
• Amniotic Fluid Index (AFI) ≥24 cm 1, 2

Severity classification:

• Mild: AFI 24-29.9 cm or DVP 8-11 cm
• Moderate: AFI 30-34.9 cm or DVP >11 cm
• Severe: AFI ≥35 cm or DVP >16 cm 2, 3

Diagnostic Workup

When polyhydramnios is identified, a thorough evaluation should include:

1. Detailed fetal anatomical survey to identify structural anomalies
2. Fetal echocardiography to rule out cardiac defects
3. Maternal diabetes screening (oral glucose tolerance test)
4. TORCH serology to identify congenital infections
5. Consideration of genetic testing based on clinical findings 1

For twin pregnancies, evaluate for twin-twin transfusion syndrome (TTTS), characterized by:

• Polyhydramnios in recipient twin (DVP >8 cm)
• Oligohydramnios in donor twin (DVP <2 cm) 4

Management Approach

Surveillance

• For mild idiopathic polyhydramnios: Antenatal fetal surveillance is not routinely required 1, 2
• For moderate to severe polyhydramnios: Regular antenatal surveillance is recommended
• For monochorionic diamniotic twin pregnancies: Begin ultrasound surveillance at 16 weeks of gestation and continue at least every 2 weeks until delivery 4, 1

Interventions

1. Expectant management is appropriate for mild idiopathic polyhydramnios 1, 2

2. Amnioreduction should be considered only for:

   • Severe maternal discomfort
   • Maternal dyspnea
   • Not for the sole purpose of prolonging pregnancy 1, 2, 5

   Note: Amnioreduction has a complication rate of approximately 10.9%, including preterm delivery within 48 hours in 5.4% of cases 5

3. Pharmacological therapy:

   • NSAIDs (such as indomethacin) are NOT recommended for the sole purpose of decreasing amniotic fluid 1, 2
   • If maternal NSAID therapy is considered, close monitoring with fetal echocardiography is mandatory 1

4. For TTTS:

   • Stage I: Expectant management with weekly surveillance
   • Stage II-IV: Fetoscopic laser surgery between 16-26 weeks 4, 1

Delivery Planning

• For mild idiopathic polyhydramnios:

  • Allow spontaneous labor at term
  • If induction is planned, it should not occur before 39 weeks without other indications
  • Mode of delivery based on standard obstetric indications 1, 2

• For severe polyhydramnios:

  • Delivery at a tertiary care center is recommended due to the significant possibility of fetal anomalies 1, 2

Etiology and Associated Risks

Common causes of polyhydramnios include:

• Gestational diabetes mellitus
• Fetal anomalies (especially those affecting swallowing)
• Congenital infections
• Twin-twin transfusion syndrome
• Genetic syndromes 1, 6, 7

Polyhydramnios is associated with:

• Increased perinatal mortality (OR 5.8)
• Increased risk of stillbirth (OR 1.8)
• Preterm labor
• Premature rupture of membranes
• Abnormal fetal presentation
• Cord prolapse
• Postpartum hemorrhage 1, 7

Special Considerations

• In cases of antenatal Bartter syndrome, polyhydramnios typically develops between 20-30 weeks of gestation 4
• Polyhydramnios may be transient in some conditions, such as gestational diabetes with good glycemic control 6
• Moderate-severe polyhydramnios warrants delivery at a tertiary care center due to the high association with fetal anomalies 1, 2

By following this structured approach to diagnosis and management, clinicians can optimize outcomes for pregnancies complicated by polyhydramnios.