What is the management for a fetus with intrauterine growth restriction (IUGR) and a cerebroplacental ratio (CPR) less than 1 with a normal umbilical artery Doppler at 36 weeks gestation?

Management of IUGR with CPR <1 and Normal Umbilical Artery Doppler at 36 Weeks

Plan for delivery at 37 weeks of gestation, as the Society for Maternal-Fetal Medicine recommends this timing for fetal growth restriction with decreased diastolic flow or severe FGR (EFW <3rd percentile), regardless of normal umbilical artery Doppler findings. 1, 2

Delivery Timing Algorithm

If Severe FGR (EFW <3rd percentile):

• Deliver at 37 weeks even with normal umbilical artery Doppler 1, 2
• Do not delay beyond 37 weeks hoping for additional growth, as stillbirth risk increases significantly 2, 3

If Moderate FGR (EFW 3rd-10th percentile):

• Deliver at 38-39 weeks with normal umbilical artery Doppler 1, 4
• The CPR <1 indicates brain-sparing physiology from placental insufficiency but does not change delivery timing when umbilical artery Doppler remains normal 2

Surveillance Protocol Until Delivery

Weekly monitoring is required from now until delivery: 1

• Umbilical artery Doppler weekly to detect deterioration to absent or reversed end-diastolic velocity 1, 2
• Cardiotocography (NST) weekly after viability for FGR without absent/reversed end-diastolic velocity 1
• If absent end-diastolic velocity develops: Increase Doppler to 2-3 times per week and deliver immediately at 33-34 weeks 1, 2
• If reversed end-diastolic velocity develops: Hospitalize, give corticosteroids, perform CTG 1-2 times daily, and deliver at 30-32 weeks 1

Why CPR Does Not Change Management

The Society for Maternal-Fetal Medicine explicitly recommends against using middle cerebral artery Doppler (which determines CPR) for routine clinical management of FGR (GRADE 2B). 1, 2

• Multiple systematic reviews found insufficient high-quality evidence and wide variations in CPR accuracy for predicting perinatal outcomes 2
• CPR <1 confirms placental insufficiency and fetal adaptation to hypoxemia, but umbilical artery Doppler remains the primary determinant of delivery timing 2
• Current guidelines prioritize umbilical artery Doppler over CPR because it has superior evidence for guiding delivery decisions 2

Mode of Delivery

Vaginal delivery with continuous electronic fetal monitoring is appropriate if umbilical artery end-diastolic flow remains present. 2, 4

• Cesarean delivery is not routinely indicated for FGR alone unless other obstetric indications arise or fetal intolerance of labor occurs 2, 4
• If absent or reversed end-diastolic velocity develops, cesarean delivery should be strongly considered based on the entire clinical scenario 1, 2

Critical Pitfalls to Avoid

• Do not rely solely on CPR to guide delivery timing - current guidelines do not support this practice (GRADE 2B) 1, 2
• Do not delay delivery beyond 37 weeks in confirmed FGR, even with reassuring testing, as stillbirth risk increases 2, 3
• Do not miss deterioration to absent/reversed end-diastolic velocity - this requires immediate change in management with earlier delivery 1, 5
• Do not assume normal umbilical artery Doppler means normal outcome - late preterm IUGR fetuses may not show Doppler changes before fetal demise occurs after 34 weeks 3