RESUMO
INTRODUCTION: The excessive gestational weight gain predisposes to overweight and obesity postpartum, this becomes a worldwide public health problem. OBJECTIVE: To analyze gestational weight pattern and body fat in adolescents and adult women, to identify the group that would have major weight and body fat gain. MATERIAL AND METHODS: A prospective cohort study done in 64 adolescent < or = 18 years and 48 adult women. Anthropometric evaluation was realized, at 20, 24, 28, 32, 36 and 38 gestational weeks with weight and body fat percentage. Patients signed letter informed consent. RESULTS: In adolescents weight and BMI were smaller (p < 0.001), and their gestational fat gain was bigger than in the adult women (5.31 vs. 4.12 kg; p < 0.001). Pre-gestational BMI (beta = 0.459, EE = 0.089, p = 0.001), and age group (beta = - 1.400, EE = 0.735, p = 0.060) were associated to fat percentage variability. The adolescents with low weight and BMI > or = 85th percentile showed a greater gain of weight in respect to which is classified as normal weight (18.0 and 15.5 vs. 12.0 kg; p = 0.018). 54.7% of the adolescents and 64.6% of adults did gain excessive weight, more than the recommended according pre-gestational BMI. CONCLUSIONS: Age and pregestational BMI conditioned the body fat change. More than half of the patients included exceeded the recommended weight gain. The overweight or excessive weight gain adolescents have increased risk of postpartum retention weight than adult women in the same conditions.