Influence of Maternal Pre-pregnancy and Children’s Body Mass Index on Cognitive Functions

Abstract

Both pre-pregnancy maternal body mass index (BMI) and higher BMI of children themselves are reported to be associated with children’s lower cognitive functions. The current study aimed to explore whether pre-pregnancy maternal BMI is directly related to children’s cognitive functions or whether this relationship is mediated by children’s BMI. Of the 1258 participants in the Hamamatsu Birth Cohort Study for Mothers and Children (HBC Study), 857 children who completed measurements at age 6 years were included. Cognitive functions were measured at age 9 using the Wechsler Intelligence Scale for Children—Fourth Edition (WISC–IV); full-scale IQ (FSIQ), and scores of the four subscales (verbal comprehension, perceptual reasoning, working memory, and processing speed) were obtained. The results of counterfactual-based mediation analysis showed a significant natural direct effect between maternal BMI and children’s FSIQ and a natural indirect effect via children’s BMI. The proportion of mediation was estimated to explain 49.8%. Similar direct and indirect effects were observed in the perceptual reasoning and working memory subscales. The association between higher maternal BMI and lower cognitive functions in children was partially mediated by higher BMI in children. On the other hand, higher maternal BMI had a direct negative effect on children’s cognitive functions.