Management at 38 Weeks with Asymmetric FGR, Normal AFI, and Ductus Arteriosus S/D 2.11
Proceed to delivery at 37-38 weeks gestation based on the presence of asymmetric growth restriction with abdominal circumference at the 2nd percentile, regardless of the ductus arteriosus Doppler findings. 1, 2
Critical Assessment Required
The ductus arteriosus Doppler S/D ratio of 2.11 should not guide management decisions. The Society for Maternal-Fetal Medicine explicitly recommends against using ductus venosus, middle cerebral artery, or uterine artery Doppler for routine clinical management of fetal growth restriction—only umbilical artery Doppler has Level I evidence for guiding delivery timing. 2, 3
Immediate Actions Needed
Obtain umbilical artery Doppler immediately to determine the appropriate delivery timing, as this is the only vessel with Level I evidence showing a 29% reduction in perinatal mortality (RR 0.71,95% CI 0.52-0.98) in FGR management. 2
Perform cardiotocography (NST or biophysical profile) today to assess immediate fetal well-being, as weekly testing is recommended for FGR without absent/reversed end-diastolic velocity. 1, 2
Delivery Timing Algorithm Based on Umbilical Artery Doppler
The timing of delivery depends entirely on umbilical artery Doppler findings:
If Umbilical Artery Doppler Shows Normal Flow
- Deliver at 38-39 weeks when estimated fetal weight is between 3rd-10th percentile with normal Doppler. 1, 2
- Since the patient is already at 38 weeks, proceed with delivery planning now. 2
If Umbilical Artery Doppler Shows Decreased Diastolic Flow
- Deliver at 37 weeks for decreased diastolic flow (elevated resistance >95th percentile but not absent). 1, 2
- Since the patient is already beyond 37 weeks, deliver immediately. 2, 3
If Umbilical Artery Doppler Shows Absent End-Diastolic Velocity (AEDV)
- Deliver urgently, preferably by cesarean section, as the recommended delivery window is 33-34 weeks and the fetus is now at 38 weeks—far beyond the safe window. 2, 3
- At term with AEDV, there is no benefit to attempting vaginal delivery. 3
If Umbilical Artery Doppler Shows Reversed End-Diastolic Velocity (REDV)
- Emergency cesarean delivery is required immediately, as the recommended delivery window is 30-32 weeks and this represents critical placental dysfunction. 2, 3
- Do not attempt labor induction or allow spontaneous labor, as the fetus cannot tolerate the stress of contractions. 3
Additional Diagnostic Considerations
The severe asymmetry (abdominal circumference at 2nd percentile while estimated fetal weight is at 20th percentile) strongly suggests placental insufficiency rather than constitutional smallness. 1, 4
The abdominal circumference <10th percentile alone meets criteria for FGR diagnosis according to the 2020 Society for Maternal-Fetal Medicine guidelines. 2, 4
Severe FGR with estimated fetal weight <3rd percentile warrants delivery at 37 weeks regardless of Doppler findings. 1, 2
Mode of Delivery Planning
Cesarean delivery should be strongly considered if umbilical artery Doppler shows absent or reversed end-diastolic velocity, as 75-95% of such pregnancies require emergency cesarean for intrapartum fetal heart rate abnormalities. 2, 3
Continuous electronic fetal monitoring during labor is mandatory if vaginal delivery is attempted, as FGR fetuses are at high risk for intrapartum compromise even with normal antepartum testing. 2
Common Pitfalls to Avoid
Do not delay delivery based on the ductus arteriosus Doppler value—this vessel lacks evidence for guiding clinical management. 2, 3
Do not rely solely on normal AFI (8.23) or reassuring cardiotocography to defer delivery, as normal fetal heart rate testing does not exclude progression of growth restriction. 2
Do not use the normal estimated fetal weight (20th percentile) to dismiss the severity—the severe asymmetry with abdominal circumference at 2nd percentile indicates placental insufficiency requiring delivery. 1, 4
Do not discharge without obtaining umbilical artery Doppler—this is the only evidence-based surveillance tool that should guide delivery timing. 2, 3