What is the recommended management for a fetus with intra‑uterine growth restriction?

Management of Fetal Growth Restriction (IUGR)

Once fetal growth restriction is diagnosed, management centers on serial umbilical artery Doppler surveillance to stratify risk and determine delivery timing, with the specific Doppler pattern dictating both monitoring intensity and gestational age at delivery. 1

Initial Diagnostic Workup

Confirm the Diagnosis

• Define FGR as estimated fetal weight or abdominal circumference below the 10th percentile using population-based references (Hadlock formula). 1
• Verify accurate gestational age with first-trimester dating ultrasound to ensure correct percentile calculations. 2

Structural and Genetic Assessment

• Perform detailed anatomic ultrasound (CPT 76811) for all FGR diagnosed before 32 weeks gestation, as chromosomal abnormalities and structural malformations account for approximately 20% of early-onset cases. 1, 3
• Offer chromosomal microarray analysis for unexplained isolated FGR diagnosed before 32 weeks, as this is the highest-yield genetic test. 1, 3
• If fetal malformations or polyhydramnios accompany FGR at any gestational age, offer chromosomal microarray analysis. 1, 3

Infectious Workup

• Do not routinely screen for toxoplasmosis, rubella, or herpes in the absence of specific risk factors—these tests have low yield. 1, 3
• Perform CMV PCR testing only if amniocentesis is already being done for genetic testing, as CMV is the most common infectious cause worth investigating. 1, 3

Maternal Evaluation

• Screen for hypertensive disorders (blood pressure, urinalysis) as preeclampsia strongly correlates with placental insufficiency. 2
• Assess for other maternal conditions that impair uteroplacental perfusion. 1

Surveillance Protocol: The Doppler-Driven Algorithm

Umbilical artery Doppler is the only surveillance modality with Level I evidence showing a 29% reduction in perinatal mortality and must be initiated immediately upon FGR diagnosis. 4, 2, 3

Normal Umbilical Artery Doppler

• Doppler frequency: Weekly 1, 4, 3
• Cardiotocography (NST or BPP): Weekly after viability 1, 4
• Growth ultrasound: Every 3-4 weeks (minimum 2-week intervals) 4
• Delivery timing: 38-39 weeks if EFW remains between 3rd-10th percentile 1, 4, 3

Decreased End-Diastolic Velocity (Elevated Resistance >95th Percentile)

• Doppler frequency: Weekly 1, 3
• Cardiotocography: Twice weekly or more frequently 4, 3
• Delivery timing: 37 weeks gestation 1, 4, 3
• This also applies to severe FGR with EFW <3rd percentile regardless of Doppler pattern. 1, 4

Absent End-Diastolic Velocity (AEDV)

• Doppler frequency: 2-3 times per week 1, 4, 3
• Cardiotocography: Twice weekly minimum; some protocols recommend daily monitoring 4, 3
• Delivery timing: 33-34 weeks gestation 1, 4, 3
• Immediate interventions if <34 weeks:
  • Administer betamethasone 12 mg IM, repeat after 24 hours 4, 2
  • Observe 48-72 hours after corticosteroid administration before delivery unless acute deterioration occurs 4, 2
  • Give magnesium sulfate 4-6 g IV loading dose for neuroprotection if delivery anticipated <32 weeks 1, 4, 2
  • Consider hospitalization for intensified surveillance 1, 4

Reversed End-Diastolic Velocity (REDV)

• Immediate hospitalization is mandatory 1, 4, 2
• Doppler frequency: 3 times per week with daily consultant review 4, 2
• Cardiotocography: 1-2 times daily 1, 4
• Delivery timing: 30-32 weeks gestation 1, 4, 3
• Immediate interventions:
  • Administer betamethasone 12 mg IM, repeat after 24 hours 4, 2
  • Give magnesium sulfate 4-6 g IV loading dose for neuroprotection 1, 4, 2
  • Observe 48-72 hours after corticosteroids unless acute deterioration mandates earlier delivery 4, 2

Additional Doppler Studies: What NOT to Use

Do not use middle cerebral artery, ductus venosus, or uterine artery Doppler for routine clinical decision-making, as randomized trials have not demonstrated outcome benefit despite their ability to detect physiologic changes. 4, 3 The umbilical artery is the only vessel with Level I evidence for mortality reduction. 4, 2

Antenatal Corticosteroids and Neuroprotection

• Administer antenatal corticosteroids (betamethasone or dexamethasone) if delivery is anticipated before 33 6/7 weeks (GRADE 1A recommendation). 1, 3
• Also give corticosteroids between 34 0/7 and 36 6/7 weeks if delivery is likely within 7 days and no prior course has been given. 1
• Administer intrapartum magnesium sulfate for neuroprotection when delivery is expected before 32 weeks (GRADE 1A recommendation). 1, 4, 2, 3

Mode of Delivery

Strongly consider cesarean delivery for FGR complicated by absent or reversed end-diastolic velocity, as these fetuses have severely limited physiologic reserve and high rates (75-95%) of intrapartum compromise. 1, 4, 2, 3 Labor induction is contraindicated in the presence of absent or reversed flow. 2

For FGR with normal or decreased (but present) diastolic flow, vaginal delivery may be attempted with continuous electronic fetal monitoring. 4

Interventions to Avoid

• Do not use low-molecular-weight heparin solely for prevention of recurrent FGR—evidence does not support this intervention. 1, 3
• Do not prescribe sildenafil for in utero treatment of FGR—it lacks efficacy data and may be harmful. 1, 3
• Do not recommend activity restriction or bed rest—these provide no benefit and may cause harm. 1, 3

Critical Pitfalls

• Never rely on cardiotocography or biophysical profile alone without Doppler assessment. Normal fetal heart rate patterns can persist even with severe placental dysfunction evident on Doppler; heart rate changes occur late in the deterioration sequence. 4, 2
• Do not delay delivery beyond the gestational ages specified for each Doppler finding. Perinatal mortality exceeds 20% with expectant management of absent flow beyond 34 weeks. 2
• Do not use umbilical artery Doppler as a screening tool in low-risk pregnancies—it is validated only after FGR is diagnosed. 4, 2
• Obtain cord arterial and venous pH at all FGR deliveries to document fetal acid-base status. 2
• Send the placenta for histopathologic examination in every case to guide counseling for future pregnancies. 2

Special Consideration: FGR with Oligohydramnios

When FGR is complicated by oligohydramnios (deepest vertical pocket <2 cm or AFI <5 cm), prognosis worsens significantly as this indicates severe placental dysfunction and chronic fetal hypoxemia. 2, 3 At 35 weeks or beyond with FGR and oligohydramnios, proceed with immediate delivery after corticosteroid administration. 3