Management of Small for Gestational Age (SGA) and Low Birthweight

Maternal Risk Factors and Antenatal Screening

The American College of Obstetricians and Gynecologists recommends early pregnancy risk selection, with 5 of 6 guidelines recommending low-dose aspirin for women with major risk factors for placental insufficiency, and smoking cessation interventions should be prioritized as a modifiable risk factor 3
Maternal schizophrenia increases the odds of SGA (OR 1.64-1.54 depending on study quality) 1

The American College of Obstetricians and Gynecologists defines SGA as estimated fetal weight (EFW) or abdominal circumference (AC) <10th percentile for gestational age, and severe FGR is defined as EFW <3rd percentile, associated with stillbirth rates up to 2.5% 2
Four of six international guidelines recommend using customized EFW rather than population references 3
Umbilical artery Doppler should be performed when SGA is suspected, as abnormal findings confirm placental insufficiency and guide management intensity 2, 4

For normal Doppler (EFW 3rd-10th percentile), serial umbilical artery Doppler every 2 weeks is recommended, and delivery at 38-39 weeks gestation for isolated SGA with normal Doppler 5
For decreased end-diastolic flow, weekly umbilical artery Doppler surveillance, and delivery at 37 weeks gestation 5
For absent end-diastolic velocity (AEDV), Doppler assessment 2-3 times per week, and delivery at 33-34 weeks gestation, with antenatal corticosteroids if delivery anticipated before 33 6/7 weeks 5
For reversed end-diastolic velocity (REDV), hospitalization with cardiotocography 1-2 times per day, and delivery at 30-32 weeks gestation, with magnesium sulfate for fetal neuroprotection for pregnancies <32 weeks 5

FGR alone is not an indication for cesarean delivery when umbilical artery end-diastolic flow is present, but continuous fetal monitoring in labor is recommended for all SGA pregnancies, and cesarean delivery is recommended for very preterm FGR or severe umbilical artery Doppler abnormalities (AEDV/REDV) 5

Accurate pregnancy dating using first-trimester crown-rump length is essential before diagnosing FGR, and do not rely on fundal height alone in obese patients—proceed directly to ultrasound 2, 4
Abandon the term "intrauterine growth restriction (IUGR)" for prenatal diagnosis—use "fetal growth restriction (FGR)" instead, reserving "SGA" for newborns with birthweight <10th percentile 2