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

Abstract

To determine whether adolescent pregnancy is associated with maternal-fetal growth competition for nutrients the relationship between maternal weight gain and birth weight was analyzed through data on 9694 Black and White adolescents and adults enrolled in the 1959-65 US National Collaborative Perinatal Project. The ratio of birth weight to pregnancy weight gain in both Black and White adolescents (34.7 and 31.8 respectively) was significantly smaller than that in Black and White adults (37.0 and 38.2 respectively). The regression coefficients of pregnancy weight gain and birth weight in the young adolescents (14.0-16.9 years) was significantly smaller (21.6 g/kg of weight gain for Blacks and 20.0 g/kg for Whites) than in older adolescents (17.0-18.9 years) (23.3 g/kg of weight gain for Blacks and 23.5 g/kg for Whites) and adults (19.9-24.9 years) (24.5 g/kg of weight gain for Blacks and 25.0 g/kg for Whites). The adult pregnancy weight gain associated with the average birth weight (3100 g for Blacks and 3400 g for Whites) was 10 kg. In young adolescents pregnancy weight gain associated with average birth weight was about 15 kg for Blacks and 16 kg for Whites. These findings suggest that young adolescents transfer a significantly smaller proportion of their pregnancy weight gain to their fetuses than older adolescents and adults. The lower birth weights of infants of young adolescents are presumed to reflect a maternal-fetal competition for nutrients.