Proportionality of small for gestational age babies as a predictor of neonatal mortality and morbidity.

Neonatal mortality and morbidity of 2609 babies who weighed less than the fifth centile for gestational age were studied in order to evaluate the relationship between the type of intrauterine growth retardation and the short-term prognosis after birth. Of these babies, 1175 had both a birthweight and head circumference below the fifth centile ('proportionately small'); the others, whose body weight was below but head circumference above the fifth centile, were defined as 'disproportionately small'. The former group showed a consistently higher risk of death during the neonatal period. Morbidity defined by birth asphyxia, respiratory distress and neonatal infections was higher in those proportionately small babies who were delivered at term. The picture reversed for hyperbilirubinaemia, which was more frequent among disproportionately small babies. Proportionality, defined on the basis of the correspondence between birthweight and head circumference centiles, appears to be a simple and non-invasive clinical method to identify babies who are at higher risk of adverse outcome.