Delivery Timing for Dichorionic Diamniotic Twins with Selective Growth Restriction and Normal Dopplers
Delivery should occur at 37 weeks of gestation for this dichorionic diamniotic twin pregnancy with severe selective fetal growth restriction (EFW <3rd percentile) despite normal umbilical artery Dopplers in both twins. 1, 2
Rationale for 37-Week Delivery
The Society for Maternal-Fetal Medicine recommends delivery at 37 weeks of gestation specifically for pregnancies with severe FGR when the estimated fetal weight is less than the 3rd percentile, regardless of normal Doppler findings. 1, 2 This recommendation applies to your case where one twin has an EFW at the 4th percentile and abdominal circumference less than the 3rd percentile, meeting criteria for severe growth restriction. 1
The presence of normal umbilical artery Dopplers does not change this recommendation when severe growth restriction is present. 1, 2 While normal Dopplers are reassuring and indicate the absence of placental insufficiency severe enough to cause abnormal flow patterns, they do not eliminate the increased risk of stillbirth and adverse outcomes associated with severe growth restriction. 1
Key Clinical Distinctions
Why Not Wait Until 38-39 Weeks?
The 38-39 week delivery recommendation applies only to FGR with EFW between the 3rd and 10th percentile with normal Dopplers. 1, 2, 3 Your case falls below this threshold with measurements at or below the 3rd-4th percentile, placing it in the severe FGR category that warrants earlier delivery. 1
Dichorionic vs Monochorionic Considerations
This is a dichorionic diamniotic twin pregnancy, which means each twin has its own placenta and the growth restriction in one twin reflects isolated placental insufficiency affecting only that twin. 4, 5 Unlike monochorionic twins, there is no shared placental circulation that could lead to twin-twin transfusion syndrome or other vascular complications. 1
The normally grown twin will be delivered at 37 weeks alongside the growth-restricted twin, which is earlier than the typical 38 weeks recommended for uncomplicated dichorionic twins, but this is necessary to prevent stillbirth of the severely growth-restricted twin. 1, 4
Surveillance Until Delivery
While awaiting delivery at 37 weeks, the following surveillance protocol should be implemented:
- Weekly umbilical artery Doppler evaluation for the growth-restricted twin, given the severe FGR (EFW <3rd percentile). 2, 3
- Weekly cardiotocography (non-stress testing) after viability for both twins. 2, 3
- Serial growth ultrasounds every 2-3 weeks to monitor for further deterioration, though delivery timing should not be delayed beyond 37 weeks. 3
If umbilical artery Dopplers deteriorate to show absent end-diastolic velocity (AEDV), delivery should be expedited to 33-34 weeks. 1, 2 If reversed end-diastolic velocity (REDV) develops, immediate hospitalization and delivery at 30-32 weeks is indicated. 1, 2
Delivery Preparation
Antenatal Corticosteroids
Antenatal corticosteroids are not indicated at 37 weeks of gestation, as this is beyond the recommended window of 34 0/7 to 36 6/7 weeks for late preterm delivery. 2, 3 Corticosteroids should only be administered if delivery becomes necessary before 36 6/7 weeks due to Doppler deterioration or other complications. 3
Mode of Delivery
Cesarean delivery should be considered based on standard obstetric indications (malpresentation, prior cesarean, etc.), but the presence of severe FGR with normal Dopplers alone does not mandate cesarean delivery. 1, 3 However, if Dopplers deteriorate to show AEDV or REDV, cesarean delivery should be strongly considered due to the 75-95% rate of intrapartum fetal heart rate decelerations requiring emergency cesarean in such cases. 1, 2
Common Pitfalls to Avoid
Do not delay delivery beyond 37 weeks hoping for additional fetal growth. 1 The risk of stillbirth in severely growth-restricted fetuses increases significantly with expectant management, and a large cohort study demonstrated that delivery at 37 weeks decreases stillbirth rates in the presence of FGR. 1
Do not use singleton growth charts for twin pregnancies. 6, 7 Twin-specific growth references better identify fetuses at risk for adverse neonatal outcomes, as singleton charts can overdiagnose FGR in twins and lead to unnecessary interventions. 6 However, in your case with measurements at the 3rd-4th percentile, severe growth restriction is present regardless of which reference is used. 6
Do not rely solely on biophysical profile or amniotic fluid volume for surveillance. 1, 3 While oligohydramnios may indicate uteroplacental insufficiency, umbilical artery Doppler and cardiotocography are the primary surveillance modalities for FGR. 1, 3
Outcome Expectations
Research on dichorionic twins with selective FGR and normal Dopplers shows that inter-twin EFW discordance ≥15% is associated with higher rates of preterm delivery before 32 and 34 weeks, though this typically occurs when Dopplers are abnormal. 5 With normal Dopplers and delivery planned at 37 weeks, neonatal outcomes are generally favorable for both twins. 5
The normally grown twin will experience iatrogenic late preterm delivery at 37 weeks, which carries minimal risk compared to the substantial risk of stillbirth for the growth-restricted twin if delivery is delayed. 4 Studies demonstrate that delaying delivery in dichorionic twins with selective FGR to increase gestational age of the normal twin is only appropriate when the growth-restricted twin's condition permits and Dopplers remain normal, but not beyond 37 weeks when severe FGR is present. 4