Maternal pre-pregnancy body mass index, gestational weight gain influence birth weight

Background: Evidence suggests that pre-pregnancy body mass index and gestational weight gain have impact on pregnancy and birth weight, yet whether maternal gestational weight gain has a differential effect on the rates of adverse birth weight among women with different pre-pregnancy body mass index categories are unknown.

Methods: We selected 1617 children matched with their mothers as study subjects. The subjects were divided into three categories: weight gain below the American Institute of Medicine guidelines, weight gain within the American Institute of Medicine guidelines and weight gain above the American Institute of Medicine guidelines.

Results: The prevalence of pre-pregnancy underweight and overweight/obese women was 16.3% and 12.3%. And nearly 15.2% of the women had gestational weight gain below American Institute of Medicine guideline, 52.1% of the women had gestational weight gain above American Institute of Medicine guideline. Maternal overweight and obese was associated with increased risk for macrosomia and large-for-gestational age. Women had gestational weight gain below American Institute of Medicine guideline were more likely to have low birth weight and small-for-gestational age than women who had gestational weight gain within American Institute of Medicine guideline. Furthermore, the risks for macrosomia and large-for-gestational age were increased in women with above American Institute of Medicine guideline. And for women with a normal weight before pregnancy, gestational weight gain above the American Institute of Medicine guidelines were associated with higher rates of macrosomia and large-for-gestational age, compared with the women of similar pre-pregnancy weight category but with gestational weight gain within the American Institute of Medicine guidelines.

Conclusions: Women with abnormal pre-pregnancy body mass index and gestational weight gain are at risk for adverse birth weight outcomes. Moreover, gestational weight gain has a differential effect on the rates of adverse birth weight outcomes between women of different pre-pregnancy body mass index categories.