Adolescent pregnancy is associated with adverse birth outcomes. Less is known about its influence on maternal growth and nutritional status. We determined how pregnancy and lactation during adolescence affects postmenarcheal linear and ponderal growth and body composition of 12-19 y olds in rural Bangladesh. In a prospective cohort study, anthropometric measurements were taken among primigravidae (n = 229) in the early first trimester of pregnancy and at 6 mo postpartum. Randomly selected never-pregnant adolescents (n = 458) of the same age and time since menarche were measured within 1 wk of these assessments. Annual changes in anthropometric measurements were compared between the 2 groups adjusting for confounders using mixed effects regression models. The mean +/- SD age and age at menarche of adolescents were 16.3 +/- 1.6 y and 12.7 +/- 1.2 y, respectively. Unlike pregnant girls who did not grow in height (-0.09 +/- 0.08 cm/y), never-pregnant girls increased in stature by 0.35 +/- 0.05 cm/y. The adjusted mean difference between the 2 groups was 0.43 +/- 0.1cm (P < 0.001). Similarly, whereas never-pregnant girls gained BMI, mid-upper arm circumference, and percent body fat, pregnant girls declined in every measurement by 6 mo postpartum, resulting in adjusted mean +/- SD differences in annual changes of 0.62 +/- 0.11 kg/m(2), 0.89 +/- 0.12 cm, and 1.54 +/- 0.25%, respectively (all P < 0.001). Differences in changes in all anthropometric measurements except height were greater among adolescents whose first pregnancy occurred <24 mo vs. > or =24 mo since menarche (BMI, -1.40 +/- 0.18 vs. -0.60 +/- 0.11 kg/m(2); all interaction terms, P < 0.05). Pregnancy and lactation during adolescence ceased linear growth and resulted in weight loss and depletion of fat and lean body mass of young girls.