High Gestational Weight Gain Does Not Improve Birth Weight in a Cohort of African American Adolescents

Abstract

Pregnant teenagers are at risk of delivering low-birth-weight infants because of the nutritional demands of their own growth and because they are often poor, members of a minority, have a low educational level, and receive suboptimal prenatal care. For this reason, they often are advised to gain weight up to the upper level of the recommended range. On the other hand, black women in particular are at increased risk of postpartum weight retention, leading to being overweight or obese and increasing the risk of chronic disease. Thus, the weight gain that would be ideal for both pregnant black teenagers and their infants is unknown. In this retrospective study, Nielson and colleagues reviewed the prenatal record of 815 blacks no more than 17 years of age who received prenatal care at an inner-city maternity clinic in the years 1990 through 2000. Participants were classified on the basis of the body mass index (BMI) as being underweight (less than 19.8 kg/m 2 ), average weight (19.8-26.0 kg/m 2 ), overweight (26.1-29.0 kg/m 2 ), or obese (more than 29 kg/m 2 ) and their pregnancy outcomes were analyzed. Of 815 subjects, 82.5% were primiparous, 41% were uninsured, and their BMIs ranged from 14.8 to 49 kg/m 2 . The mean gestational age at delivery was 38.8 weeks, and the mean birth weight was 3062 g. Thirty-seven percent of infants weighed less than 3000 g, and 16% were classified as small for gestational age. Across all BMI categories, women who gained in the lower half of the recommended weight had significantly larger infants and fewer infants weighing <3000 g than mothers who gained less than the recommended weight. However, gaining more weight (weight gain in the upper half or greater than the recommended weight gain) did not significantly increase birthweight or reduce the number of infants weighing <3000 g. Close to 60% of mothers delivering at term and three fourths of high-BMI mothers gained weight in the upper half or above the recommended range. After controlling for possible confounding factors, the adjusted odds ratio of having a small-for-gestational-age infant decreased from 2.31 (95% confidence interval = 1.22-4.37) in teenagers who gained less than the recommended weight to 0.68 (0.34-1.35) for those who gained greater than the recommended weight. In both low- and high-BMI teens, increasing from below to within the recommended weight range was associated with an increase in birth weight of approximately 260 g. The investigators suggest that black adolescents in early pregnancy who are underweight or of average weight be advised to gain weight within the recommended range. Overweight teens, in contrast, should avoid gaining excessive body weight while pregnant.