Mediation of the Association Between Interpregnancy Weight Change and Perinatal Outcomes by Gestational Weight Gain

Abstract

Interpregnancy weight gain is associated with perinatal outcomes in the subsequent pregnancy. The objective of this study was to examine mediation of these associations by gestational weight gain (GWG) in the subsequent pregnancy. A population-based retrospective cohort of 72,254 deliveries to parous women in Nova Scotia, 2004-2022, was used to investigate interpregnancy body mass index (BMI) change in relation to small and large birthweight for gestational age (SGA and LGA), preterm delivery, Caesarean section, and neonatal injury. G-computation was used for analysis. Interpregnancy BMI change outside the referent category (-1 to 1 kg/m2) increased risk of LGA and was protective of SGA and preterm delivery. Associations with SGA, LGA and neonatal injury were inconsistently mediated by GWG: the natural direct effect was stronger than the total causal effect. Limiting interpregnancy weight change is associated with an increase in GWG, resulting in a small trade-off for minimizing the risk of outcomes.