What is the management of Fetal Growth Restriction (FGR)?

Management of Fetal Growth Restriction (FGR)

The management of fetal growth restriction requires a structured approach based on umbilical artery Doppler findings, with specific timing of delivery determined by the severity of growth restriction and Doppler abnormalities. 1

Diagnosis and Classification

FGR is defined as:

• Estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age 1
• Severe FGR: EFW below the 3rd percentile 1

Classification by timing:

• Early-onset FGR: Diagnosed <32 weeks gestation
• Late-onset FGR: Diagnosed ≥32 weeks gestation 1, 2

Initial Evaluation

1. Detailed ultrasound examination

   • Recommended for early-onset FGR (<32 weeks) as up to 20% of cases are associated with fetal or chromosomal abnormalities 1

2. Genetic testing

   • Offer prenatal diagnostic testing with chromosomal microarray analysis (CMA) when:
     • FGR is detected with fetal malformation and/or polyhydramnios (any gestational age) 1
     • Unexplained isolated FGR diagnosed at <32 weeks 1

3. Infectious disease evaluation

   • Not recommended to screen for toxoplasmosis, rubella, or herpes without other risk factors
   • PCR for cytomegalovirus recommended in women with unexplained FGR who undergo amniocentesis 1

Monitoring Protocol

Umbilical Artery Doppler Surveillance

For EFW between 3rd-10th percentile:

• Initial Doppler assessment every 1-2 weeks for 1-2 weeks
• If stable, can decrease to every 2-4 weeks 1
• Weekly cardiotocography (CTG) testing after viability 1
• Consider EFW assessment every 2 weeks; at minimum every 3-4 weeks 1

For EFW <3rd percentile (severe FGR):

• Weekly umbilical artery Doppler evaluation 1
• Weekly CTG testing 1
• Consider EFW assessment every 2 weeks 1

For abnormal umbilical artery Doppler findings:

• Decreased end-diastolic velocity: Weekly Doppler evaluation 1
• Absent end-diastolic velocity (AEDV): Doppler assessment 2-3 times per week 1
• Reversed end-diastolic velocity (REDV): Hospitalization, daily CTG (at least 1-2 times/day), antenatal corticosteroids, and consideration of delivery 1

Other Doppler Studies

• Ductus venosus, middle cerebral artery, or uterine artery Doppler are not recommended for routine clinical management of early or late-onset FGR 1
• These may provide additional information in specialized centers but should not guide routine care 1

Timing of Delivery

Timing is based on umbilical artery Doppler findings and severity of growth restriction:

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

   • Deliver at 38-39 weeks gestation 1

2. Decreased diastolic flow (without AEDV/REDV) or severe FGR (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

Delivery Considerations

1. Mode of delivery

   • Systematic cesarean deliveries for FGR are not universally recommended 3
   • For pregnancies with FGR complicated by AEDV/REDV, cesarean delivery should be considered based on the clinical scenario 1

2. Antenatal corticosteroids

   • Recommended if delivery is anticipated before 33 6/7 weeks 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

3. Magnesium sulfate

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

Maternal Monitoring

• Monitor closely for development of hypertensive disorders, as maternal hypertension is common in early-onset FGR (present in 50% during pregnancy and 70% at delivery) 4
• Maternal hypertension is associated with earlier delivery, lower birthweights, and poorer outcomes 4

Pitfalls and Caveats

1. Avoid unnecessary activity restriction

   • Activity restriction is not recommended for in utero treatment of FGR 1

2. Avoid ineffective treatments

   • Low-molecular-weight heparin and sildenafil are not recommended for prevention or treatment of FGR 1, 4

3. Recognize the importance of gestational age

   • The single most important prognostic factor in preterm fetuses with growth restriction is gestational age at delivery 4
   • There is a 1-2% increase in intact survival for every additional day spent in utero up until 32 weeks 4

4. Standardized protocols improve outcomes

   • Following a standardized protocol for diagnosis and management is associated with more favorable outcomes 4

5. Consider long-term implications

   • Children born with FGR have higher risks of minor cognitive deficits, school problems, and metabolic syndrome in adulthood 3

By following this structured approach to FGR management, focusing on appropriate monitoring intervals and evidence-based timing of delivery based on Doppler findings, clinicians can optimize outcomes for these high-risk pregnancies.