What are the Green Top guidelines for Fetal Growth Restriction (FGR) management?

Green Top Guidelines for Fetal Growth Restriction (FGR) Management

The Society for Maternal-Fetal Medicine (SMFM) recommends a structured approach to FGR management based on gestational age, severity of growth restriction, and umbilical artery Doppler findings to optimize fetal outcomes and reduce morbidity and mortality. 1

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
• A detailed obstetrical ultrasound examination 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

Diagnostic Testing

• Fetal diagnostic testing, including chromosomal microarray analysis (CMA), should be offered when FGR is detected with fetal malformation, polyhydramnios, or both, regardless of gestational age 1
• Prenatal diagnostic testing with CMA should be offered when unexplained isolated FGR is diagnosed at <32 weeks of gestation 1
• Screening for toxoplasmosis, rubella, or herpes in pregnancies with FGR is not recommended in the absence of other risk factors 1
• PCR for cytomegalovirus (CMV) is recommended in women with unexplained FGR who elect diagnostic testing with amniocentesis 1

Surveillance

• Once FGR is diagnosed, serial umbilical artery Doppler assessment should be performed to assess for deterioration 1
• With decreased end-diastolic velocity (flow ratios greater than the 95th percentile) or in pregnancies with severe FGR (EFW less than the 3rd percentile), weekly umbilical artery Doppler evaluation is recommended 1
• Doppler assessment should be performed up to 2-3 times per week when umbilical artery absent end-diastolic velocity (AEDV) is detected due to potential for deterioration and development of reversed end-diastolic velocity (REDV) 1
• Weekly cardiotocography (CTG) testing after viability is suggested for FGR without AEDV/REDV, with increased 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

Management of REDV

• In the setting of REDV, hospitalization, administration of antenatal corticosteroids, heightened surveillance with CTG at least 1-2 times per day, and consideration of delivery depending on the entire clinical picture is recommended 1

Timing of Delivery

• For FGR with EFW between the 3rd and 10th percentile and normal umbilical artery Doppler: delivery at 38-39 weeks of gestation 1
• For FGR with an umbilical artery Doppler waveform with decreased diastolic flow but without AEDV/REDV or with severe FGR (EFW less than the 3rd percentile): delivery at 37 weeks of gestation 1
• For FGR with AEDV: delivery at 33-34 weeks of gestation 1
• For FGR with REDV: delivery at 30-32 weeks of gestation 1

Mode of Delivery

• For pregnancies with FGR complicated by AEDV/REDV, cesarean delivery should be considered based on the entire clinical scenario 1
• Continuous fetal monitoring in labor is recommended for all FGR cases 1

Antenatal Interventions

• Antenatal corticosteroids are recommended if delivery is anticipated before 33 6/7 weeks of gestation or for pregnancies between 34 0/7 and 36 6/7 weeks of gestation in women at risk of preterm delivery within 7 days 1
• Intrapartum magnesium sulfate for fetal and neonatal neuroprotection is recommended for women with pregnancies that are <32 weeks of gestation 1

Prevention and Treatment

• Low-molecular-weight heparin is not recommended for the sole indication of prevention of recurrent FGR 1
• Sildenafil or activity restriction is not recommended for in utero treatment of FGR 1
• Low-dose aspirin is recommended for women at increased risk of preeclampsia, which may also reduce the risk of FGR 1, 2

Special Considerations

• Maternal hypertensive disease is common in early-onset FGR (present in 50-70% of cases) and is associated with poorer outcomes, including earlier delivery and lower birthweights 1
• Women with early-onset FGR should be closely monitored for the 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, with an increase of 1-2% in intact survival for every additional day spent in utero up until 32 weeks of gestation 1