Gender differences in neurodevelopmental outcomes among extremely preterm, extremely-low-birthweight infants

To determine whether gender-specific responses to perinatal and neonatal events and exposures explain the male disadvantage in early childhood outcomes.

Infants were in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network, born 1/1/1997-12/31/2000, <28 wk, with neurodevelopmental follow-up at 18-22 mo corrected age. We evaluated and compared univariate and multivariate associations of risk factors with neurodevelopmental outcomes for girls and boys. Neurodevelopmental impairment (NDI) was one or more of the following: moderate--severe cerebral palsy (CP), Bayley Mental (MDI) or Psychomotor (PDI) Development Indices <70, deafness or blindness.

Boys (n=1216) were more likely than girls (n=1337) to have adverse outcomes (moderate--severe CP: 10.7% vs 7.3%; MDI < 70: 41.9% vs 27.1%; NDI: 48.1% vs 34.1%). Major risk factors were also more common in boys. Independent multivariate associations of risk factors with outcome differed by gender, but not consistently in favor of girls. In multivariate models including both girls and boys, male gender remained an independent risk factor for MDI < 70 (2.0, 95% CI 1.6-2.5) and NDI (1.8, 95% CI 1.5-2.2).

Perinatal, neonatal and early childhood factors confer similar incremental risk or protection to boys and girls, but boys appear to have inherently greater baseline risk. Unmeasured biological variables likely contribute to the preterm male neurodevelopmental outcome disadvantage.