Effects of biologic and experiential conditions on the pattern of growth in weight of premature and full-term infants.

In this exploratory study we examined the contribution of biologic and experiential conditions to the pattern of growth in weight for premature and full-term infants. The three components of the pattern were: (a) the infant's weight level; (b) the linear growth rate; and (c) the quadratic growth rate. Biologic conditions were maturity at birth and gender. Experiential conditions included variables in the mother's caregiving and the infant's feeding behavior, nutrient intake, and acuity of illness. At 1, 4, 8, and 12 months, premature infants (n = 61) weighed significantly less than full-term infants (n = 53), but neither linear nor quadratic rates of weight gain were significantly different from the rates for the full-term infants. Multilevel analytic models showed that female gender significantly affected weight level and linear and quadratic growth rates. Negative affect and behavior in both the mother and the infant significantly increased the linear rate of weight gain. The interaction of several experiential conditions with the two biologic conditions, birth maturity and gender, affected growth outcomes. Further exploration of the model with a larger sample is indicated to enable simultaneous testing of biologic and experiential conditions. Copyright 2001 John Wiley & Sons, Inc.