Reduction of birth weight among infants born to adolescents: maternal-fetal growth competition.

Previous investigations have indicated that the birth weights of infants born to adolescent mothers are lower than those of infants born to adult mothers. Some investigators have attributed these differences to socioeconomic factors, while others have postulated that the low birth weights of infants born to adolescent mothers are a consequence of the maternal-fetal growth competition for nutrients.'-3 Studies conducted among Peruvian adolescents found that still-growing teenagers transfer a lower proportion of their pregnancy weight gain to their fetus than do adult^.^.^ Also, studies of teenagers in the United States found that young adolescents transfer a lower proportion of their pregnancy weight gain to their newborns than do older adolescents and adults.48 However, a recent report9 based on a study of 141 black adolescents concluded that young adolescents contributed equal or greater amounts of their gestational weight gain to their fetuses than older adolescents. Hence, it is not clear whether there is a maternal-fetal growth competition for nutrients among young adolescents. To clarify this issue we have analyzed the relationship of material weight gain to the birth weights of 9694 black and white young adolescents, older adolescents, and adults derived from the 1959-1 965 National Collaborative Perinatal Project.