Growth and development in very preterm infants : the influence of infant, maternal and medical factors
It is generally acknowledged that infants born very preterm are at a high risk of developmental delay. It has been suggested that the first few months of life ex-utero might constitute a "sensitive period" during which growth rate could influence later outcome measures including cognitive development. This study investigated the early growth of a sample of 90 infants born very preterm and the developmental status (at 18 months of age) of 81 of those infants (mean gestational age 29.4 weeks; mean birth weight 1283g). Two main issues were addressed. One concerned the relative contribution of various early infant, maternal and medical factors to rate of growth up to 3-months corrected age. The other issue was the extent to which these early factors, as well as early growth rate, were predictive of developmental status at 18 months of age (again corrected for gestation), using the Mental Development Index of the Bayley Scales. Analyses revealed that there were few significant predictors of early growth among the variables that were examined. Infants who had required more intensive medical care during the neonatal period showed a slower growth rate than the more robust infants. Breast-fed infants grew slower from birth to term, but thereafter grew significantly better, resulting in no discernable difference over the whole 5-7 month period. None of the infant behavioural, maternal or social variables examined appeared to be related to early growth. Infants who were born lighter-for-gestation grew faster than the infants who were heavier for gestational age. At the 18-month follow-up assessment this very preterm sample performed poorly overall in comparison to published norms for full term infants. When regression analyses were performed, weight at 3-months of age was found to be predictive of developmental status at 18-months (even when concurrent weight was taken into account), whereas actually being born growth retarded was not found to be a risk factor for poorer developmental outcome. This supports the concept of a "sensitive period" during the first few months of life, when growth rate may influence developmental outcome. Other significant predictors of developmental outcome were gender, early brain scan and mean parental height.