The Effect of Gestational Weight Gain on Persistent Increase in Body Mass Index in Adolescents: A Longitudinal Study

Background: Weight retention after pregnancy is a concern for adolescents who may be entering adulthood at unhealthy weights. Methods: We studied associations between each of three measures: prepregnancy body mass index (BMI), gestational weight gain (GWG), and postpregnancy BMI in a longitudinal follow-up of an adolescent pregnancy study cohort. BMI and GWG were compared using t-tests and linear regression. Results: Among 91 adolescents, mean prepregnancy BMI was 24.6 [standard deviation (SD) 5.7] and mean GWG was 15.5kg [SD 6.3]. Overall, prepregnancy BMI was not significantly related to GWG (p=0.145). Among 42 teens with postpregnancy weight data, within 4 years of their first delivery, mean postpregnancy BMI was 26.3 [SD 5.0] with an average BMI increase of 2.0 points [SD 5.1] (p=0.013) from prepregnancy. Within 4 years of their first delivery, 45% of teens moved to a higher BMI category. For every 4.5kg (10 lb) increase in GWG, BMI within 4 years increased on average by 1.6 points (p=0.006). The association persisted (1.0 points, p=0.049) after controlling for prepregnancy BMI. Conclusions: Teens experienced an increase in BMI from prepregnancy to within 4 years after their first delivery, and this increase was related to GWG. Adolescent mothers are at risk for developing and maintaining unhealthy BMI after pregnancy, which may be amplified by GWG.