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.