Small for Gestational Age (SGA)
SGA infants are those with a birth weight below the 10th percentile for gestational age. They may be constitutionally small and healthy, or affected by intrauterine growth restriction (IUGR) due to pathological causes. Careful distinction is essential. 👶
🧬 Causes
- Maternal smoking 🚬 or substance misuse
- Maternal malnutrition 🍽️
- Placental insufficiency or infarction
- Intrauterine infections (TORCH)
- Chromosomal anomalies (e.g., Trisomy 21, Turner’s)
- Preeclampsia / maternal hypertension
- Multiple pregnancy (e.g., twin–twin transfusion)
⚠️ Risks
- ↑ Perinatal mortality
- Hypothermia 🥶 and hypoglycemia
- Birth asphyxia / meconium aspiration
- Polycythemia & jaundice
- Developmental delay 📉
- Later-life metabolic syndrome (HTN, T2DM, CVD)
🧪 Investigations
- Ultrasound biometry (AC, HC, FL, EFW)
- Doppler velocimetry (umbilical artery, ductus venosus)
- Infection screen (TORCH, syphilis)
- Karyotyping if syndromic features
🩺 Management
- Serial growth scans + Doppler monitoring
- Maternal optimisation: nutrition, smoking cessation, BP control
- Induction or cesarean if severe IUGR or abnormal Dopplers
- Postnatal: monitor glucose, temperature, haematocrit
- Developmental follow-up for learning/behavioural concerns
💡 Pearls:
- SGA ≠ always pathological: many are constitutionally small but healthy.
- Recurrent or severe SGA should trigger screening for maternal disease, placental dysfunction, or genetic syndromes.