Influence of growth status and placental function on birth weight of infants born to young still-growing teenagers.

To investigate the determinants of fetal maturation of infants born to adolescent mothers, we studied the obstetric population attended at the Maternity Hospital of Lima, Peru. From this population we selected for inclusion in this study a sample of 412 adolescent mothers ranging in age from 13 to 15 yr. These subjects were selected because the anthropometric measurements of their parents were obtained at the time the adolescents were being attended for delivery. Based on the height measurements of the teenagers' mothers and fathers, the adolescents were classified as either still growing or growth completed depending on whether their height was less or greater than their mothers' height. Infants of young adolescent mothers who had not completed their expected growth in height were significantly lighter in birth weight than those born to adolescent mothers who had completed their growth. Multiple regression and path analyses revealed that the effects of weight gain and placenta weight on birth weight were more effective among the infants born to adolescent mothers who had not completed their growth in height. These data suggest that the reduction in birth weight among immature still-growing adolescents may result from both a decreased net availability of nutrients and/or an inability of the placenta to function adequately for active fetal growth, which results in a retarded fetal growth.