Timing of Delivery for Fetal Growth Restriction (FGR) with Abnormal Dopplers
The timing of delivery for FGR with abnormal Dopplers should follow a specific protocol based on the severity of Doppler abnormalities: deliver at 37 weeks for decreased diastolic flow, 33-34 weeks for absent end-diastolic velocity (AEDV), and 30-32 weeks for reversed end-diastolic velocity (REDV). 1
Delivery Timing Based on Doppler Findings
Umbilical Artery Doppler Abnormalities
- Normal Doppler with FGR: Deliver at 38-39 weeks gestation when estimated fetal weight (EFW) is between 3rd and 10th percentile with normal umbilical artery Doppler 1
- Decreased diastolic flow: Deliver at 37 weeks gestation when umbilical artery Doppler shows decreased diastolic flow but without absent/reversed end-diastolic velocity or when severe FGR with EFW <3rd percentile 1
- Absent end-diastolic velocity (AEDV): Deliver at 33-34 weeks gestation as neonatal morbidity/mortality rates with AEDV exceed complications of prematurity at this gestational age 1
- Reversed end-diastolic velocity (REDV): Deliver at 30-32 weeks gestation as this finding indicates severe placental dysfunction with high risk of fetal demise 1
Surveillance Protocol Before Delivery
Monitoring Frequency
- For FGR with normal umbilical artery Doppler: Serial umbilical artery Doppler assessment every 2 weeks 1
- For decreased end-diastolic velocity or severe FGR (EFW <3rd percentile): Weekly umbilical artery Doppler evaluation 1
- For absent end-diastolic velocity: Doppler assessment 2-3 times per week 1
- For reversed end-diastolic velocity: Hospitalization with cardiotocography 1-2 times per day 1
Additional Monitoring
- Weekly cardiotocography (CTG) testing after viability for FGR without absent/reversed end-diastolic velocity 1
- Increased CTG frequency when FGR is complicated by absent/reversed end-diastolic velocity 1
- Middle cerebral artery (MCA) Doppler may be useful in late-onset FGR (>32 weeks) but is not recommended for routine clinical management 1, 2
Interventions Prior to Delivery
- Antenatal corticosteroids: Administer if delivery is anticipated before 33 6/7 weeks or between 34 0/7 and 36 6/7 weeks in women at risk of delivery within 7 days 1
- Magnesium sulfate: Administer for fetal and neonatal neuroprotection for pregnancies <32 weeks gestation 1
Mode of Delivery Considerations
- For pregnancies with FGR complicated by absent/reversed end-diastolic velocity, cesarean delivery should be considered based on the clinical scenario 1
- FGR fetuses with abnormal Dopplers are at increased risk for intrapartum fetal heart rate decelerations, emergency cesarean delivery, and metabolic acidemia 1
- Studies report rates of intrapartum fetal heart rate decelerations requiring cesarean delivery in 75-95% of pregnancies with FGR and AEDV/REDV 1
Special Considerations
Early-onset FGR (<32 weeks)
- Progression of umbilical artery Doppler abnormality determines clinical acceleration 2
- Abnormal ductus venosus Doppler precedes deterioration of biophysical variables and stillbirth 2
- For delivery before 26 weeks or at 500g, coordinate care between maternal-fetal medicine and neonatology services 1
- Neonatal survival increases from 13% at 24 weeks to 43% at 25 weeks and 58-76% at 26 weeks 1
Late-onset FGR (>32 weeks)
- Middle cerebral artery Doppler abnormalities may precede deterioration and stillbirth 2
- From 34-38 weeks, randomized evidence on optimal delivery timing is lacking 2
- After 38 weeks, the balance of neonatal versus fetal risks favors delivery 2
Common Pitfalls and Caveats
- Avoid using ductus venosus, middle cerebral artery, or uterine artery Doppler for routine clinical management of early or late-onset FGR 1
- Do not rely solely on biophysical profile (BPP) or cardiotocography for surveillance 1
- Remember that growth-restricted fetuses with abnormal uterine artery Doppler waveforms have a 4-fold increased risk of adverse neonatal outcome 3
- The cerebroplacental ratio (CPR) may help identify fetuses at highest risk for early delivery, but is not universally recommended for clinical decision-making 4
By following these evidence-based guidelines for timing of delivery in FGR with abnormal Dopplers, clinicians can optimize outcomes by balancing the risks of prematurity against the risks of continued intrauterine exposure to placental insufficiency.