Infant and caregiving factors affecting weight-for-age and motor development of full-term and premature infants at 1 year post-term.

Guided by a theoretical process model, we examined direct and indirect effects of infants' biologic condition and experience, the caregiving environment, and caloric intake variables on two outcomes, weight-for-age and motor development, for 52 full-term and 47 premature infants at 12 months post-term age. For full-term infants, birth weight and infant expression of positive affect and behavior during feeding had predicted positive direct effects on weight-for-age. Infant regulation of negative affect and behavior had an unexpected negative effect on this outcome. For premature infants, severity of acute illness, mother's regulation of negative affect and feeding behavior, and caloric intake affected weight-for-age in unpredicted directions. Caregiving variables had indirect effects, through caloric intake, on both outcomes only for premature infants. The findings suggest the theoretical process model differs for premature infants and full-term infants, both in the contributing variables and in the processes of effects.