Small for gestational age neonates - Are we missing some by only using standard population growth standards and does it matter?

Objectives. Birth weight below the 10th percentile on growth charts based on population norms or small for gestational age (SGA) is associated with adverse perinatal outcome. We compare the association among neonatal mortality, morbidity and SGA as determined by currently used percentiles based on population standards (method A) and customised birth weight percentiles (method B). Methods. Study of outcomes of SGA neonates from a cohort of 6125 consecutive pregnancies, analysed in function of the method (A or B) used to diagnose SGA. Results. There were 831 SGA infants, 84% were born at term and the majority were of European origin (61.4%). By method A, there was a sixfold decrease in the prevalence of SGA babies (2.3%) compared with method B (13.5%). After correcting for prematurity, SGA infants diagnosed by method B alone (not identified by standard population method) still constituted a high proportion of infants with hypothermia and hypoglycaemia (p<0.05). Conclusion. Customised charts identified six times more SGA infants than standard charts. These infants, considered appropriately grown by standard charts, are at a significantly higher risk of morbidity.