Pregnancy increases BMI in adolescents of a population-based birth cohort

Evidence from developed countries suggests that adolescents grow while pregnant and that their growth is associated with increased weight gain and fat storage, but this has never been examined in girls from developing countries. Adolescents born in 1982 in Pelotas, Brazil, are being followed in a birth cohort study. Information on social and biological determinants of nutritional status was collected in early life. Both in 1997 and in 2001, 464 girls were located through household visits, 16% of whom had had a pregnancy in this period. Changes in height, weight, and BMI between 1997 and 2001 were analyzed in relation to the occurrence of pregnancy, after adjustment for previous anthropometric status, as well as social and biological characteristics. The average gains were 2.0 ± 2.0 cm in height, 3.1 ± 5.9 kg in weight, and 0.7 ± 2.2 kg/m² in BMI. Each pregnancy was associated with a reduction of 0.46 cm on height gain from 1997 to 2001 (P = 0.02). Girls who became pregnant gained 2.25 kg more than all others (P = 0.004). There was a clear association between pregnancy and BMI change. A single pregnancy was associated with an increase of 0.81 kg/m² (P = 0.01) and 2 or more pregnancies were associated with an increase of 1.58 kg/m² (P = 0.02). Teenage pregnancy was associated with an important increase in BMI. Given the growing epidemic of obesity in low- and middle-income countries, particularly among women, efforts to reduce teenage pregnancy may also contribute to preventing overweight.