At what gestational age is delivery typically recommended for dichorionic-diamniotic (di/di) twins?

Timing of Delivery for Dichorionic-Diamniotic (Di/Di) Twins

Dichorionic-diamniotic twins should be delivered at 37 0/7 to 38 0/7 weeks of gestation when uncomplicated. 1

Rationale for Delivery Timing

The timing of delivery for twin pregnancies must balance the risks of prematurity against the risks of stillbirth. For di/di twins specifically:

• Perinatal outcomes improve as gestational age advances to 38 weeks 2
• The lowest perinatal mortality rate for twins occurs at 37-38 weeks 2
• Continuing pregnancy beyond 38 weeks increases stillbirth risk more than it decreases neonatal mortality risk 3

Factors That Modify Delivery Timing

Complications That Warrant Earlier Delivery

1. Fetal Growth Restriction:

   • Severe FGR (EFW <3rd percentile): Deliver at 37 weeks 4
   • FGR with abnormal umbilical artery Doppler but without absent/reversed end-diastolic flow: Deliver at 37 weeks 4
   • FGR with absent end-diastolic velocity: Deliver at 33-34 weeks 4
   • FGR with reversed end-diastolic velocity: Deliver at 30-32 weeks 4

2. Growth Discordance:

   • Despite higher absolute risks of stillbirth and neonatal death with growth discordance, the optimal timing of delivery remains 37-38 weeks for di/di twins 3

Monitoring Recommendations

• Serial ultrasound assessment of fetal growth every 4 weeks 5
• Weekly non-stress tests or biophysical profiles starting at 34 weeks for dichorionic twins 5
• If growth restriction is diagnosed, weekly umbilical artery Doppler evaluation is recommended 6

Mode of Delivery Considerations

• Trial of labor is appropriate for di/di twins when the first twin is in cephalic presentation at ≥32 weeks' gestation 1
• Cesarean delivery should be considered when:
  • First twin is in breech presentation 1
  • Estimated fetal weight exceeds 4500g in diabetic women or 5000g in non-diabetic women 6

Antenatal Corticosteroids

• Consider administering a course of antenatal corticosteroids for fetal maturation if delivery is anticipated between 24 and 33 6/7 weeks 4
• This is particularly important for pregnancies undergoing invasive interventions or with complications 4

Common Pitfalls to Avoid

1. Extending pregnancy beyond 38 weeks: This increases stillbirth risk without significant benefit in neonatal outcomes
2. Premature delivery without indication: Delivery before 37 weeks without specific complications increases neonatal morbidity
3. Failing to distinguish between di/di and mono/di twins: Monochorionic twins require earlier delivery (36-37 weeks) due to higher complication rates 1, 5
4. Inadequate monitoring: Weekly testing should begin at 34 weeks for dichorionic twins 5

In summary, the evidence supports delivery of uncomplicated di/di twins at 37-38 weeks of gestation, with earlier delivery indicated for specific complications such as growth restriction or abnormal Doppler studies. This approach optimizes outcomes by balancing the risks of prematurity against the risks of stillbirth.