Postnatal factors associated with failure to thrive in term infants in the Avon Longitudinal Study of Parents and Children.

OBJECTIVE To assess the contribution of postnatal factors to failure to thrive in infancy. METHODS 11 900 infants from the Avon Longitudinal Study of Parents and Children (ALSPAC), born at 37-41 weeks' gestation, without major malformations and with a complete set of weight measurements in infancy (83% of the original ALSPAC birth cohort) were studied. Conditional weight gain was calculated for the periods from birth to 8 weeks and 8 weeks to 9 months. Cases of growth faltering were defined as those infants with a conditional weight gain below the 5th centile. RESULTS Analysis yielded 528 cases of growth faltering from birth to 8 weeks and 495 cases from 8 weeks to 9 months. In multivariable analysis, maternal factors predicting poor infant growth were height <160 cm and age >32 years. Growth faltering between birth and 8 weeks was associated with infant sucking problems regardless of the type of milk, and with infant illness. After 8 weeks of age, the most important postnatal influences on growth were the efficiency of feeding, the ability to successfully take solids and the duration of breast feeding. CONCLUSIONS The most important postnatal factors associated with growth faltering are the type and efficiency of feeding: no associations were found with social class or parental education. In the first 8 weeks of life, weak sucking is the most important symptom for both breastfed and bottle-fed babies. After 8 weeks, the duration of breast feeding, the quantity of milk taken and difficulties in weaning are the most important influences.