What are the Royal College of Obstetricians and Gynaecologists (RCOG) guidelines for managing Fetal Growth Restriction (FGR)?

RCOG Guidelines for Fetal Growth Restriction (FGR) Management

The Royal College of Obstetricians and Gynaecologists recommends a systematic approach to diagnosing, monitoring, and delivering pregnancies affected by fetal growth restriction, with timing of delivery based on umbilical artery Doppler findings and gestational age to optimize neonatal outcomes and reduce mortality.

Definition and Diagnosis

• FGR should be defined as an ultrasonographic estimated fetal weight (EFW) or abdominal circumference (AC) below the 10th percentile for gestational age 1
• Population-based fetal growth references (such as Hadlock) should be used in determining fetal weight percentiles 1
• Severe FGR is defined as EFW less than the 3rd percentile 1

Initial Assessment

• A detailed obstetrical ultrasound examination (CPT code 76811) should be performed with early-onset FGR (<32 weeks of gestation) as up to 20% of cases are associated with fetal or chromosomal abnormalities 1
• Pregnant women should be offered prenatal diagnostic testing with chromosomal microarray analysis (CMA) when:
  • FGR is detected with fetal malformation, polyhydramnios, or both, regardless of gestational age 1
  • Unexplained isolated FGR is diagnosed at <32 weeks of gestation 1
• Screening for toxoplasmosis, rubella, or herpes is not recommended in pregnancies with FGR in the absence of other risk factors 1
• PCR for cytomegalovirus should be performed in women with unexplained FGR who elect diagnostic testing with amniocentesis 1

Surveillance Protocol

Umbilical Artery Doppler Monitoring

• Once FGR is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration 1
• For EFW between 3rd-9th percentile with normal Doppler: umbilical artery Doppler every 1-2 weeks initially; if stable, can decrease to every 2-4 weeks 1
• For severe FGR (EFW <3rd percentile) or decreased end-diastolic velocity: weekly umbilical artery Doppler evaluation 1
• With absent end-diastolic velocity (AEDV): Doppler assessment 2-3 times per week 1
• With reversed end-diastolic velocity (REDV): hospitalization, antenatal corticosteroids, cardiotocography (CTG) 1-2 times daily, and consideration of delivery 1

Additional Monitoring

• Weekly cardiotocography (CTG) testing after viability for FGR without AEDV/REDV 1
• Increase CTG frequency when FGR is complicated by AEDV/REDV or other comorbidities 1
• Doppler assessment of the ductus venosus, middle cerebral artery, or uterine artery is not recommended for routine clinical management of early- or late-onset FGR 1, 2
• Fetal growth assessment should be performed at least every 3-4 weeks; consider 2-week intervals in severe FGR or with abnormal umbilical artery Doppler 1

Timing of Delivery

• For FGR with normal umbilical artery Doppler (EFW 3rd-10th percentile): deliver at 38-39 weeks 1
• For FGR with decreased diastolic flow (but without AEDV/REDV) or severe FGR (EFW <3rd percentile): deliver at 37 weeks 1
• For FGR with absent end-diastolic velocity (AEDV): deliver at 33-34 weeks 1
• For FGR with reversed end-diastolic velocity (REDV): deliver at 30-32 weeks 1

Delivery Considerations

• For pregnancies with FGR complicated by AEDV/REDV, cesarean delivery should be considered based on the entire clinical scenario 1
• Antenatal corticosteroids should be administered if delivery is anticipated:
  • Before 33 6/7 weeks of gestation 1
  • Between 34 0/7 and 36 6/7 weeks in women at risk of preterm delivery within 7 days who have not received a prior course 1
• Intrapartum magnesium sulfate should be given for fetal and neonatal neuroprotection for pregnancies <32 weeks of gestation 1

Classification and Phenotypes

• Early-onset FGR (<32 weeks at diagnosis) and late-onset FGR (≥32 weeks) represent two distinct clinical phenotypes with differences in:
  • Severity and progression 3, 4
  • Association with preeclampsia 4
  • Sequence of fetal deterioration 2, 5
• Early-onset FGR typically shows progressive deterioration in umbilical artery Doppler, while late-onset FGR may present with subtle Doppler abnormalities 2, 5

Common Pitfalls to Avoid

• Failing to distinguish between constitutional small for gestational age (SGA) and pathological FGR 3, 6
• Relying solely on umbilical artery Doppler for diagnosis of FGR, as this detects only severe early-onset forms 3, 4
• Delaying delivery in cases with REDV, which significantly increases stillbirth risk 1
• Overlooking late-onset FGR, which may present with subtle abnormalities but still contributes to adverse perinatal outcomes 5
• Using inconsistent definitions and management protocols, which can lead to practice variability and suboptimal outcomes 4