Associations of Maternal Postpartum Weight Retention and Its Components With Child BMI z-Score by In Utero Exposure to Maternal Overweight/Obesity and Gestational Diabetes.

OBJECTIVE: This study examined the association between maternal postpartum weight retention (PPWR) and child BMI z-score, assessed whether this relationship was modified by in utero exposure to maternal overweight/obesity or gestational diabetes mellitus (GDM), and evaluated the relative contributions of gestational weight gain (GWG) and postdelivery weight change (PDWC). METHODS: This secondary analysis used data from the Health After Pregnancy (HAPi) Study and included 219 mother-child dyads. Dyads were classified into three groups based on maternal weight status and GDM during the index pregnancy: normal weight without GDM (NW-No GDM), overweight/obese without GDM (Ow/Ob-No GDM), and overweight/obese with GDM (GDM). PPWR was defined as maternal weight measured 4-10 years postpartum minus baseline pregnancy weight. GWG and PDWC were examined as components of PPWR. Adjusted moderation models tested whether associations between maternal weight change measures and child BMI z-score differed by exposure group, overall and stratified by child sex. RESULTS: Maternal PPWR was associated with child BMI z-score (p = 0.012), and this association differed by exposure group (interaction p = 0.030). Greater PPWR was associated with higher child BMI z-score in the NW-No GDM and Ow/Ob-No GDM groups, but not in the GDM group. GWG, but not PDWC, showed a similar pattern. The PPWR-exposure interaction was significant among girls (interaction p = 0.005), but not boys. CONCLUSIONS: The association between maternal PPWR and child BMI z-score differed by in utero exposure group and was driven primarily by GWG, highlighting pregnancy as a potential intervention window.