What are the recommendations for antepartum management of multifetal (multiple fetus) gestation?

Antepartum Management of Multifetal Gestation

Comprehensive ultrasound surveillance with specific protocols based on chorionicity is the cornerstone of antepartum management for multifetal gestations, with monochorionic twins requiring more intensive monitoring starting at 16 weeks of gestation. 1

Initial Assessment and Chorionicity Determination

• First trimester evaluation is critical:
  • Transabdominal and transvaginal ultrasound are recommended when twin pregnancy is known or suspected 1
  • Chorionicity and amnionicity determination must be performed in the first trimester when accuracy is highest 1
  • Documentation of "lambda" or "T" sign to distinguish dichorionic from monochorionic twins 1

Surveillance Protocols Based on Chorionicity

Dichorionic Twin Pregnancies

• Anatomy scan at 18-22 weeks' gestation 1
• Growth ultrasounds every 4 weeks starting at 20 weeks 1
• Cervical length assessment to identify risk for preterm birth 1
• Duplex Doppler velocimetry only when growth discrepancy is detected 1

Monochorionic Twin Pregnancies

• More intensive monitoring required:
  • Ultrasound surveillance starting at 16 weeks' gestation 1
  • Screening every 2 weeks until delivery 1
  • Each scan must include:
    • Amniotic fluid volumes on both sides of intertwin membrane
    • Presence/absence of urine-filled bladders
    • Umbilical artery Doppler studies 1
    • Middle cerebral artery peak systolic velocity (MCA-PSV) measurements to screen for TAPS 1
  • Fetal echocardiography to screen for cardiac anomalies 1

Specific Complications Requiring Monitoring

Twin-Twin Transfusion Syndrome (TTTS)

• Screen for TTTS in all monochorionic pregnancies starting at 16 weeks 1
• Signs to monitor:
  • Discordant amniotic fluid volumes (oligohydramnios/polyhydramnios)
  • Absence of visible bladder in donor twin
  • Abnormal Doppler studies 1
• Management based on staging:
  • Stage I: Weekly surveillance if asymptomatic 1
  • Stages II-IV: Referral to fetal intervention center for fetoscopic laser surgery (16-26 weeks) 1

Twin Anemia-Polycythemia Sequence (TAPS)

• Consider MCA-PSV measurements in all monochorionic twin ultrasounds from 16 weeks 1
• Diagnostic criteria: MCA-PSV >1.5 MoM in donor and <1.0 MoM in recipient 1
• Management:
  • Stage I before 32-34 weeks: Close monitoring
  • Stage II or higher: Consider referral to fetal care center 1

Growth Discordance

• Significant discordance defined as ≥20% difference in estimated fetal weights 1
• Early predictor: >10% difference in abdominal circumference between 14-22 weeks 1
• Requires increased surveillance with:
  • Transabdominal ultrasound
  • Doppler velocimetry
  • Biophysical profile monitoring 1

Fetal Well-Being Assessment

• Antepartum fetal testing recommended in the same situations as singleton pregnancies, plus:
  • Growth restriction or discordance
  • Abnormal amniotic fluid volumes
  • Monochorionic twins (higher risk) 1
• Testing modalities:
  • Non-stress test
  • Biophysical profile
  • Doppler velocimetry (umbilical artery and ductus venosus) 1

Post-Procedure Surveillance

• After laser therapy for TTTS:
  • Weekly surveillance for 6 weeks
  • Then every-other-week surveillance
  • Include MCA-PSV to detect post-laser TAPS 1

Common Pitfalls and Caveats

1. Failure to determine chorionicity early: Chorionicity determination becomes increasingly difficult after the first trimester as the "lambda" sign may disappear 1

2. Inadequate monitoring frequency: Monochorionic twins require more frequent surveillance (every 2 weeks minimum) compared to dichorionic twins 1

3. Missing early signs of complications: Discordance in abdominal circumference >10% between 14-22 weeks is the best predictor of adverse outcomes 1

4. Overlooking specialized care needs: Multiple gestations benefit from care by experienced providers who can anticipate and manage complex problems 2

5. Inconsistent monitoring protocols: Standardized protocols based on chorionicity improve detection of complications and reduce adverse outcomes 1

The antepartum management of multifetal gestations requires specialized care with protocols tailored to chorionicity type, with particular attention to the unique complications of monochorionic twins that require early detection and prompt intervention to optimize outcomes.