What are the management guidelines for a pregnant woman with fetal growth restriction?

Management Guidelines for Fetal Growth Restriction

Fetal growth restriction (FGR) should be defined as an estimated fetal weight or abdominal circumference below the 10th percentile on ultrasound, and management must be guided by gestational age at diagnosis, Doppler findings, and severity of growth restriction. 1

Diagnostic Criteria and Initial Evaluation

• Define FGR as estimated fetal weight or abdominal circumference <10th percentile using population-based references (such as Hadlock). 1 This standardized definition ensures consistent identification across clinical settings.

• Perform a detailed anatomical ultrasound (CPT code 76811) when FGR is diagnosed before 32 weeks gestation (early-onset FGR). 1 Early-onset cases carry higher morbidity and mortality risk and require comprehensive structural assessment. 2

• Obtain umbilical artery Doppler assessment immediately upon FGR diagnosis to stratify risk and guide surveillance intensity. 1 This is the single most important prognostic tool for determining management.

Genetic and Infectious Workup

• Offer chromosomal microarray analysis when FGR occurs with fetal malformations, polyhydramnios, or both, regardless of gestational age. 1 These findings suggest underlying genetic abnormalities.

• Offer chromosomal microarray analysis for unexplained isolated FGR diagnosed before 32 weeks gestation. 1 Early-onset isolated FGR has higher rates of chromosomal abnormalities.

• Do NOT routinely screen for toxoplasmosis, rubella, or herpes in FGR pregnancies without other risk factors. 1 These tests have low yield and are not cost-effective.

• Perform PCR testing for cytomegalovirus only in women with unexplained FGR who elect diagnostic amniocentesis. 1 CMV is the most common infectious cause of FGR worth investigating.

Prevention Strategies (What NOT to Do)

• Do NOT use low-molecular-weight heparin solely for prevention of recurrent FGR. 1 Evidence does not support this intervention.

• Do NOT prescribe sildenafil or recommend activity restriction for in utero treatment of FGR. 1 These interventions are ineffective and potentially harmful.

Surveillance Protocol Based on Doppler Findings

Normal or Decreased End-Diastolic Velocity (Flow Ratios >95th Percentile)

• Perform weekly umbilical artery Doppler evaluation when end-diastolic velocity is decreased OR when severe FGR (estimated fetal weight <3rd percentile) is present. 1

• Initiate weekly cardiotocography (nonstress testing) after viability. 1 This provides reassurance of immediate fetal well-being between Doppler assessments.

Absent End-Diastolic Velocity (AEDV)

• Increase Doppler assessment frequency to 2-3 times per week. 1 AEDV indicates significant placental dysfunction requiring heightened surveillance.

• Increase cardiotocography frequency beyond weekly testing. 1 The exact frequency should be at least twice weekly given the high-risk status.

Reversed End-Diastolic Velocity (REDV)

• Hospitalize immediately upon detection of REDV. 1 This represents severe placental failure with imminent risk of fetal demise.

• Administer antenatal corticosteroids immediately if gestational age is appropriate for delivery consideration. 1

• Perform cardiotocography at least 1-2 times daily. 1 REDV requires the most intensive surveillance of all Doppler patterns.

• Prepare for delivery based on the complete clinical picture and gestational age (see delivery timing below). 1

Additional Doppler Assessments (Not Routinely Recommended)

• Do NOT use ductus venosus, middle cerebral artery, or uterine artery Doppler for routine clinical management of FGR. 1 While these may provide additional information, umbilical artery Doppler alone should guide management decisions in most cases.

Delivery Timing Algorithm

The timing of delivery must balance the risks of prematurity against the risks of ongoing placental insufficiency, guided primarily by umbilical artery Doppler findings and severity of growth restriction. 1

Early-Onset FGR (<32 weeks at diagnosis)

• Deliver at 30-32 weeks for FGR with reversed end-diastolic velocity. 1 This represents the highest-risk category requiring earliest intervention.

• Deliver at 33-34 weeks for FGR with absent end-diastolic velocity. 1 Waiting beyond this gestational age increases stillbirth risk without meaningful reduction in neonatal morbidity.

• Deliver at 37 weeks for FGR with decreased diastolic flow (but not absent/reversed) OR for severe FGR with estimated fetal weight <3rd percentile. 1

Late-Onset FGR (≥32 weeks at diagnosis)

• Deliver at 37 weeks for FGR with decreased diastolic flow OR severe FGR (estimated fetal weight <3rd percentile). 1

• Deliver at 38-39 weeks for FGR with estimated fetal weight between 3rd-10th percentile when umbilical artery Doppler is normal. 1 These fetuses have lower risk and can safely reach near-term gestation.

Mode of Delivery Considerations

• Consider cesarean delivery for FGR complicated by absent or reversed end-diastolic velocity based on the entire clinical scenario. 1 These fetuses have limited physiologic reserve and may not tolerate labor well, though vaginal delivery is not absolutely contraindicated.

Antenatal Corticosteroids and Neuroprotection

• Administer antenatal corticosteroids if delivery is anticipated before 33 6/7 weeks gestation. 1 This is critical for reducing neonatal respiratory morbidity and mortality.

• Administer antenatal corticosteroids between 34 0/7 and 36 6/7 weeks in women at risk of delivery within 7 days who have not received a prior course. 1 Late preterm steroids reduce neonatal respiratory complications.

• Administer intrapartum magnesium sulfate for fetal neuroprotection when delivery is anticipated before 32 weeks gestation. 1 This reduces the risk of cerebral palsy in surviving infants.

Special Considerations for FGR with Oligohydramnios

• FGR complicated by oligohydramnios (amniotic fluid index <5 cm or maximum vertical pocket <2 cm) significantly worsens prognosis. 3 This combination indicates severe placental dysfunction.

• At 35 weeks or beyond with FGR and oligohydramnios, proceed with immediate delivery after corticosteroid administration. 3 The risks of expectant management outweigh any benefits of continued gestation at this point.

• Coordinate immediately with neonatology for optimal resuscitation planning when FGR is complicated by oligohydramnios. 3

Critical Pitfalls to Avoid

• Do not delay delivery beyond recommended gestational ages based on Doppler findings. The evidence-based timing recommendations balance neonatal and fetal risks; deviating from these increases stillbirth risk. 1

• Do not rely on biophysical profile or nonstress testing alone without Doppler assessment in diagnosed FGR. 1 Doppler provides superior prognostic information about placental function.

• Do not assume all small fetuses are growth restricted. Some fetuses are constitutionally small and healthy. 4 However, err on the side of increased surveillance when in doubt, as the consequences of missing true FGR are severe.

• Remember that no antenatal testing can predict acute events such as placental abruption or cord accidents. 5 Even with normal surveillance, acute deterioration can occur, so patient education about warning signs (decreased fetal movement, vaginal bleeding, abdominal pain) remains essential.