What is the management and timing of delivery for early onset Fetal Growth Restriction (FGR)?

Management and Timing of Delivery for Early Onset Fetal Growth Restriction (FGR)

For early onset FGR (<32 weeks), delivery timing should be determined by umbilical artery Doppler findings: deliver at 30-32 weeks for reversed end-diastolic velocity (REDV), at 33-34 weeks for absent end-diastolic velocity (AEDV), and at 37 weeks for abnormal Doppler without AEDV/REDV or severe FGR with EFW <3rd percentile. 1

Diagnosis and Initial Evaluation

• Early onset FGR is defined as FGR diagnosed before 32 weeks gestation 2
• FGR is defined as an ultrasonographic estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age 1
• When early onset FGR is diagnosed, perform:
  • Detailed obstetrical ultrasound examination (CPT code 76811) as up to 20% of cases are associated with fetal or chromosomal abnormalities 1
  • Offer prenatal diagnostic testing with chromosomal microarray analysis (CMA) for unexplained isolated FGR diagnosed at <32 weeks 1
  • PCR for CMV in women with unexplained FGR who elect diagnostic testing with amniocentesis 1

Surveillance Protocol

1. Umbilical Artery Doppler Assessment:

   • Perform serial umbilical artery Doppler assessment to monitor for deterioration 1
   • For decreased end-diastolic velocity or severe FGR (EFW <3rd percentile): weekly umbilical artery Doppler evaluation 1
   • For absent end-diastolic velocity (AEDV): Doppler assessment 2-3 times per week 1
   • For reversed end-diastolic velocity (REDV): hospitalization, antenatal corticosteroids, cardiotocography (CTG) 1-2 times per day 1

2. Cardiotocography (CTG) Testing:

   • Weekly CTG testing after viability for FGR without AEDV/REDV 1
   • Increase frequency when FGR is complicated by AEDV/REDV or other comorbidities 1

3. Other Doppler Assessments:

   • Doppler assessment of ductus venosus, middle cerebral artery, or uterine artery is not recommended for routine clinical management 1

Timing of Delivery Algorithm

The decision for delivery in early onset FGR is based on:

1. Normal umbilical artery Doppler with EFW between 3rd-10th percentile:

   • Deliver at 38-39 weeks gestation 1

2. Abnormal umbilical artery Doppler (decreased diastolic flow) without AEDV/REDV OR severe FGR with EFW <3rd percentile:

   • Deliver at 37 weeks gestation 1

3. Absent end-diastolic velocity (AEDV):

   • Deliver at 33-34 weeks gestation 1

4. Reversed end-diastolic velocity (REDV):

   • Deliver at 30-32 weeks gestation 1

5. For periviable severe early-onset FGR (<26 weeks):

   • Coordinate care between maternal-fetal medicine and neonatology services
   • Provide comprehensive counseling on neonatal morbidity and mortality
   • Consider thresholds of 26 weeks gestation or 500g for delivery decisions 1

Mode of Delivery

• For pregnancies with FGR complicated by AEDV/REDV, consider cesarean delivery based on the clinical scenario 1
• Growth-restricted fetuses with AEDV/REDV have increased risk for decelerations in labor, emergency cesarean delivery, and metabolic acidemia 1

Antenatal Interventions

1. Antenatal Corticosteroids:

   • Administer if delivery is anticipated before 33 6/7 weeks gestation 1
   • Also recommended for pregnancies between 34 0/7 and 36 6/7 weeks in women at risk of preterm delivery within 7 days 1

2. Magnesium Sulfate:

   • Administer for fetal and neonatal neuroprotection for pregnancies <32 weeks gestation 1

3. Interventions NOT Recommended:

   • Low-molecular-weight heparin for prevention of recurrent FGR 1
   • Sildenafil or activity restriction for in utero treatment of FGR 1

Special Considerations

• Maternal hypertension is common in early-onset FGR (present in 50-70% of cases) and is an important determinant of poor outcomes 1
• Monitor closely for development of hypertensive disorders of pregnancy 1
• The single most important prognostic factor in preterm fetuses with growth restriction is the gestational age at delivery 1
• Early-onset FGR has higher perinatal morbidity and mortality rates compared to late-onset FGR 2

Pitfalls to Avoid

• Delaying diagnosis by using inappropriate growth curves - use population-based fetal growth references (such as Hadlock) 1
• Relying solely on biophysical profile for management decisions - it has high rates of false-positive and false-negative results in severe FGR 1
• Failure to recognize that neonatal survival in early-onset FGR with abnormal Doppler studies increases significantly with each week: from 13% at 24 weeks to 43% at 25 weeks and 58-76% at 26 weeks 1
• Not considering maternal hypertension in management decisions, as it significantly shortens the interval from diagnosis to delivery 1