SIGNIFICANCE OF LOW-BIRTH-WEIGHT FOR GESTATIONAL-AGE AMONG VERY PRETERM INFANTS

Objective To estimate the risk of specific adverse neonatal events res ulting from the combined effects of prematurity and low birthweight in very preterm infants (delivered at 24-31 weeks of gestation) Design A cohort study of specific adverse neonatal events in preterm infants b orn at between 24 and 31 weeks of gestation. Setting Pavia, Italy. Pop ulation Two hundred and thirty singleton infants with sonographically confirmed gestational age, delivered at 24 to 31 weeks of gestation. M ethods To evaluate the impact of a lower than expected birthweight on selected neonatal events independently of gestational age, we calculat ed birthweight standard deviation scores (differences between actual b irthweight and fitted birthweight divided by fitted standard deviation ) for each week of gestation. Results After adjustment for gestational age and other confounders, there was a significant linear trend relat ing a decreasing birthweight SDS to an increased likelihood of neonata l death, intraventricular haemorrhage, severe respiratory distress syn drome, and acidosis. Compared with infants with SDS greater than or eq ual to 0 (greater than or equal to 50th centile of birthweight), infan ts with birthweight SDS < -1 (< 16th centile) had increased odds for n eonatal death [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.42- 9.6], grade III-IV intraventricular haemorrhage (OR 17.5, 95% CI 4.04- 75.9), and neonatal acidosis (OR 3.22, 95% CI 1.41-7.4). The significa nce of birthweight SDS as a predictor of neonatal outcome, however, wa s lower than that of gestational age. Conclusions A lower than expecte d birthweight affects the likelihood of several adverse neonatal event s in very preterm infants. However, a decreasing birthweight SDS affec ts neonatal outcome less than decreasing gestation does.