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.