Weight gain during pregnancy and the black-white disparity in preterm birth.

PURPOSE: To quantify the relationship between pregnancy weight gain with early and late preterm birth and evaluate whether associations differed between non-Hispanic (NH) black and NH white women.

METHODS: We analyzed a retrospective cohort of all live births to NH black and NH white women in the United States 2011-2015 (n = 10,714,983). We used weight gain z-scores in multiple logistic regression models stratified by prepregnancy body mass index (BMI) and race to calculate population attributable risk (PAR) percentages for the contribution of high and low pregnancy weight gain to early and late preterm birth.

RESULTS: Pregnancy weight gain was related to early and late preterm birth, but associations varied by BMI and race. For early preterm birth, the PAR percentage for high pregnancy weight gain ranged from 8 to 10% in NH black women and from 6 to 8% in NH white women. There was little evidence of racial differences in late preterm birth: PAR percentages ranged from 2 to 7% in NH black women and from 3 to 7% in NH white women.

CONCLUSIONS: Moderate gestational weight gain is associated with lower rate of preterm birth, with greatest reductions for early preterm birth in NH black women.