What is the management approach for late onset fetal growth restriction (FGR)?

Management of Late-Onset Fetal Growth Restriction

The management of late-onset fetal growth restriction (FGR) requires serial umbilical artery Doppler assessment, cerebral Doppler studies, and delivery timing based on Doppler findings, with delivery recommended at 37-38 weeks for abnormal Doppler studies and at 38-39 weeks when Doppler is normal. 1, 2

Definition and Diagnosis

• Late-onset FGR is defined as FGR diagnosed at ≥32 weeks gestation 1, 3
• Diagnostic criteria include:
  • Estimated fetal weight (EFW) or abdominal circumference (AC) <10th percentile
  • EFW <3rd percentile (severe FGR)
  • AC or EFW crossing centiles by >2 quartiles on growth charts
  • Abnormal Doppler parameters (cerebral or umbilical) 1, 2

Surveillance Protocol

Ultrasound and Doppler Assessment

• Serial umbilical artery (UA) Doppler assessment is essential for monitoring deterioration 1, 2:

  • Every 2 weeks if UA Doppler is normal
  • Weekly if UA Doppler shows increased resistance (PI >95th percentile) or with severe FGR (EFW <3rd percentile)
  • 2-3 times per week with absent end-diastolic velocity (AEDV)
  • More frequently with reversed end-diastolic velocity (REDV)

• Cerebral Doppler studies are recommended for late-onset FGR 1, 2:

  • Middle cerebral artery (MCA) Doppler and cerebroplacental ratio (CPR)
  • Abnormal when MCA PI <5th percentile or CPR <5th percentile
  • Helps identify fetuses at higher risk of adverse outcomes despite normal UA Doppler

Fetal Surveillance

• Cardiotocography (CTG) monitoring 1, 2:

  • Weekly CTG after viability for FGR without AEDV/REDV
  • At least weekly if abnormal UA, MCA, CPR, or uterine artery Doppler
  • 1-2 times daily with REDV
  • Not recommended as the sole form of surveillance

• Biophysical profile (BPP) is not universally recommended as the only form of surveillance 1

Management Algorithm

Normal UA Doppler (PI <95th percentile)

• Continue surveillance:
  • UA Doppler every 2 weeks
  • MCA Doppler and CPR every 2 weeks
  • Weekly CTG
  • Delivery at 38-39 weeks gestation 1, 2

Abnormal UA Doppler (PI >95th percentile) or EFW <3rd percentile

• Intensify surveillance:
  • Weekly UA Doppler
  • Weekly MCA Doppler and CPR
  • Weekly CTG
  • Delivery at 37 weeks gestation 1, 2

Absent End-Diastolic Velocity (AEDV)

• Hospitalization recommended
• Intensify surveillance:
  • UA Doppler 2-3 times per week
  • Daily CTG
  • Administer antenatal corticosteroids if <34 weeks
  • Delivery at 33-34 weeks gestation 1, 2

Reversed End-Diastolic Velocity (REDV)

• Immediate hospitalization
• Maximum surveillance:
  • UA Doppler more frequently
  • CTG 1-2 times daily
  • Administer antenatal corticosteroids if <34 weeks
  • Consider magnesium sulfate for neuroprotection if <32 weeks
  • Delivery at 30-32 weeks gestation 1, 2

Delivery Considerations

• Mode of delivery:

  • Consider cesarean delivery with AEDV/REDV based on the entire clinical scenario 1
  • Vaginal delivery may be appropriate with normal or mildly abnormal Doppler studies

• Antenatal interventions:

  • Antenatal corticosteroids if delivery anticipated <34 weeks 1, 2
  • Consider corticosteroids between 34-37 weeks if not previously administered 1
  • Magnesium sulfate for neuroprotection if delivery <32 weeks 1, 2

Important Caveats and Pitfalls

• Avoid relying solely on umbilical artery Doppler for late-onset FGR, as it may miss cases with cerebral redistribution 1, 4
• Cerebral Doppler abnormalities often precede deterioration in late-onset FGR, unlike early-onset FGR where UA Doppler changes dominate 5
• Do not delay delivery beyond 39 weeks even with normal Doppler studies, as stillbirth risk increases markedly after this point 1
• Be aware that obesity can mask clinical detection of FGR, making ultrasound assessment more important 4
• Recognize that the majority of FGR cases (96%) occur after 32 weeks, making late-onset FGR the most common form 4

By following this structured approach to the management of late-onset FGR, clinicians can optimize outcomes by balancing the risks of intrauterine fetal compromise against the risks of iatrogenic preterm delivery.