Interpregnancy weight change: associations with severe maternal morbidity and neonatal outcomes

Prepregnancy body mass index and gestational weight gain have been linked with severe maternal morbidity, suggesting that weight change between pregnancies may also play a role, as it does for neonatal outcomes.

This study assessed the association of changes in prepregnancy body mass index between 2 consecutive singleton pregnancies with the outcomes of severe maternal morbidity, stillbirth, and small- and large-for-gestational-age infants in the subsequent pregnancy.

This observational study was based on birth records from 1,111,032 consecutive pregnancies linked to hospital discharge records in California (2007-2017). Interpregnancy body mass index change between the beginning of an index pregnancy and the beginning of the subsequent pregnancy was calculated from self-reported weight and height. Severe maternal morbidity was defined based on the Centers for Disease Control and Prevention index, including and excluding transfusion-only cases. We used multivariable log-binomial regression models to estimate adjusted risks, overall and stratified by prepregnancy body mass index at index birth.

Substantial interpregnancy body mass index gain (≥4 kg/m²) was associated with severe maternal morbidity in crude but not adjusted analyses. Substantial interpregnancy body mass index loss (>2 kg/m²) was associated with increased risk of severe maternal morbidity (adjusted relative risk, 1.13; 95% confidence interval (1.07-1.19), and both substantial loss (adjusted relative risk, 1.11 [1.02-1.19]) and gain (≥4 kg/m²; adjusted relative risk, 1.09 [1.02-1.17]) were associated with nontransfusion severe maternal morbidity. Substantial loss (adjusted relative risk, 1.17 [1.05-1.31]) and gain (1.26 [1.14-1.40]) were associated with stillbirth. Body mass index gain was positively associated with large-for-gestational-age infants and inversely associated with small-for-gestational-age infants.

Substantial interpregnancy body mass index changes were associated with modestly increased risk of severe maternal morbidity, stillbirth, and small- and large-for-gestational-age infants.