Morbidity in large-for-gestational-age neonates unidentified by standard growth charts

Objective: Large-for-gestational-age (LGA) neonates, defined by a birth weight above the 90th percentile on growth charts based on population norms, are at increased risk of adverse perinatal outcome. We compare the association between neonatal morbidity and LGA as determined either by currently used percentiles based on population standards or by customized birth weight percentiles. Study design: Retrospective cohort study of 6125 consecutive neonates delivered after 24 completed weeks in a large level 3 hospital in the United Kingdom. Using the customized method the weight percentile was calculated by adjusting for maternal height, booking weight, parity, ethnic origin, gestational age at delivery, and sex. Neonatal mortality and morbidity were the outcomes analysed in function of the method used to diagnose LGA. Results: LGA occurred in 21% of pregnancies, of which 11.4% were diagnosed by the customized method alone. Although this group had a higher rate of complications than those diagnosed by the standard method, including hypothermia (P=0.01), hypoglycaemia (P=0.04), respiratory distress syndrome (P=0.05), intraventricular haemorrhage (P<0.001) and necrotizing enterocolitis (P=0.05), the association with these complications was confounded by preterm birth and maternal diabetes and disappeared after adjusting for those factors. Conclusion: Although customized growth charts identified an extra 11.4% LGA infants who would not otherwise have been recognized, it is reassuring that they were not at increased risk of mortality or of complications associated with LGA.