Gestational weight gain as a predictor of birth and placenta weight according to prepregnancy body mass index

Objective. To study the association between gestational weight gain and different birth weight indicators considering the pre-pregnancy body mass index. It was hypothesized that a high body mass index (BMI) would modify the effect of gestational weight gain and support the advice of keeping gestational weight gain at a moderate level in case of obesity. Study design. A follow-up study of consecutively recruited women in two well defined geographical areas in Denmark. The recruitment lasted from 1984 to 1987 and 11,850 pregnant women and newborns were included in the study. The remaining analyses were restricted to non-diabetic women who gave birth between weeks 37 and 42 of gestation for whom weight gain was reported - altogether 7,122 women. Results. Birth and placenta weight were associated with gestational weight gain but with lower regression coefficients at higher BMI. The proportion of newborns with a birth weight of 4,500 grams or more increased with increasing gestational weight gain, especially in women with a BMI above 26. Conclusion. The potential benefit of a high gestational weight gain in obese patients should be balanced by the higher risk of giving birth to babies with a birth weight of more than 4,500 grams and the risk of exaggerating a pre-existing state of obesity.