At what gestational age is delivery recommended for a baby that is small for gestational age (SGA)?

Timing of Delivery for Small for Gestational Age (SGA) Babies

Delivery timing for SGA babies depends critically on umbilical artery Doppler findings and gestational age, with abnormal Doppler studies mandating earlier delivery to prevent stillbirth and severe morbidity.

Delivery Timing Based on Doppler Status

SGA with Normal Umbilical Artery Doppler

• Deliver at 38-39 weeks gestation when estimated fetal weight (EFW) is between 3rd-10th percentile with normal umbilical artery Doppler 1
• For isolated SGA (EFW <10th percentile with normal Doppler and normal amniotic fluid), delay delivery until 37 weeks but no later than 40 weeks 2
• Research demonstrates that delivery at 38-39 weeks for SGA <5th percentile is associated with optimal perinatal outcomes, as expectant management beyond this increases stillbirth risk significantly 3
• The cumulative risk of stillbirth rises from 28/10,000 ongoing SGA pregnancies at 37 weeks to 77/10,000 at 39 weeks (relative risk 2.75) 4

SGA with Decreased Diastolic Flow

• Deliver at 37 weeks gestation when umbilical artery Doppler shows decreased (but not absent) end-diastolic flow 1
• This also applies to severe SGA with EFW <3rd percentile even with normal Doppler 1
• Induction of labor with continuous cardiotocography is recommended if end-diastolic flow is present 2

SGA with Absent End-Diastolic Velocity (AEDV)

• Deliver at 33-34 weeks gestation for FGR with absent end-diastolic velocity 1, 5
• AEDV indicates severe placental insufficiency with obliteration of approximately 70% of placental tertiary villi arteries 5
• National guidelines show consensus with recommended delivery ranging from 32-34 weeks for AEDV 2
• Neonatal morbidity/mortality rates with AEDV exceed complications of prematurity at this gestational age 1
• Cesarean delivery should be strongly considered based on the clinical scenario, as 75-95% of these pregnancies require emergency cesarean for intrapartum fetal heart rate decelerations 1, 5

SGA with Reversed End-Diastolic Velocity (REDV)

• Deliver at 30-32 weeks gestation for FGR with reversed end-diastolic velocity 1, 6
• REDV represents severe placental dysfunction with extremely high risk of fetal demise 1
• National guidelines show recommended delivery ranging from 30-34 weeks for REDV 2
• Cesarean delivery is strongly recommended given the severity of compromise 6

Surveillance Protocol Before Delivery

The intensity of surveillance escalates with Doppler abnormality severity:

• Normal Doppler: Serial umbilical artery Doppler every 2 weeks 1
• Decreased end-diastolic velocity or severe SGA (EFW <3rd percentile): Weekly umbilical artery Doppler 1
• Absent end-diastolic velocity: Doppler assessment 2-3 times per week 1
• Reversed end-diastolic velocity: Hospitalization with cardiotocography 1-2 times per day 1

Essential Pre-Delivery Interventions

Corticosteroids

• Administer antenatal corticosteroids if delivery anticipated before 33 6/7 weeks 1, 6
• Also consider for deliveries between 34 0/7 and 36 6/7 weeks in women at risk of delivery within 7 days 1
• Universal agreement exists on corticosteroid use before 34 weeks across all national guidelines 2

Magnesium Sulfate

• Administer magnesium sulfate for fetal neuroprotection for pregnancies <32 weeks gestation 1, 6
• General consensus exists across guidelines for use in early-onset FGR (<32 weeks) 2

Neonatal Coordination

• Coordinate care with neonatology for optimal resuscitation planning, especially for deliveries before 26 weeks or at 500g 1, 5
• Neonatal survival at 32 weeks is excellent (95%) with low risk of neurological sequelae 6

Critical Pitfalls to Avoid

• Do not delay delivery beyond recommended gestational ages based on Doppler findings—the risk of stillbirth increases substantially with expectant management 4, 3
• Do not rely solely on biophysical profile or cardiotocography for surveillance decisions 1
• Do not use ductus venosus, middle cerebral artery, or uterine artery Doppler for routine clinical management of early or late-onset FGR 1
• Do not assume all SGA babies require immediate delivery at 37 weeks—risk stratification based on Doppler findings is essential, as low-risk SGA babies managed expectantly beyond 37 weeks have better outcomes 7

Mode of Delivery Considerations

• FGR alone is not an indication for cesarean delivery when umbilical artery end-diastolic flow is present 2
• However, high risk of cesarean exists with abnormal cerebroplacental ratio, middle cerebral artery, or umbilical artery Doppler 2
• Continuous fetal monitoring in labor is mandatory for all SGA pregnancies 2
• For very preterm FGR or severe umbilical artery Doppler abnormalities (AEDV/REDV), cesarean delivery is recommended 2, 1