From the Guidelines
The main difference between SGA (small for gestational age) and AGA (appropriate for gestational age) neonates lies in their birth weight relative to gestational age, with SGA neonates having a birth weight below the 10th percentile for their gestational age, while AGA neonates have a birth weight between the 10th and 90th percentiles, which is considered normal. According to the most recent study 1, SGA status can result from intrauterine growth restriction due to maternal factors, placental insufficiency, or fetal conditions. SGA neonates face higher risks of complications including hypoglycemia, hypothermia, polycythemia, and long-term neurodevelopmental issues.
Key Differences and Risks
- SGA neonates require more intensive monitoring of blood glucose, temperature regulation, and feeding support compared to AGA neonates.
- SGA infants may need more frequent feedings or higher caloric intake formulas to support catch-up growth.
- The definition of SGA varies slightly between countries, but generally, it is defined as a birthweight below the 10th percentile for gestational age, as seen in studies from the United Kingdom, New Zealand, Canada, Ireland, the United States, and France 2.
- Fetal growth restriction (FGR) can result from a variety of maternal, fetal, and placental conditions, and it is a leading cause of infant morbidity and mortality, with stillbirth rates approximately 1.5% in fetuses with weights below the 10th percentile, as reported in a study published in the American Journal of Obstetrics and Gynecology 3.
Management and Monitoring
- SGA infants often require specialized follow-up to monitor growth velocity and development, particularly during the first two years of life when catch-up growth is most critical.
- The use of abdominal circumference (AC) as a diagnostic criterion for FGR has been supported by evidence, with an AC of less than the 10th percentile having diagnostic accuracy similar to estimated fetal weight (EFW) less than the 10th percentile for the prediction of SGA, as found in a prospective study 3.
- Antenatal care of FGR is often complicated by the presence of maternal disease, such as hypertension, and optimal management involves balancing maternal, fetal, and neonatal risks, as outlined in a document published by the Society for Maternal-Fetal Medicine 4.