Does Maternal Weight Gain in Pregnancy Have Long-term Effects on Offspring Adiposity? A Sibling Study in a Prospective Cohort of 146,894 Men from 136,050 Families

Background: A small number of relatively small studies have found greater gestational weight gain to be associated with greater offspring body mass index (BMI; in kg/m(2)), but whether this association is caused by intrauterine mechanisms or by shared genetic and environmental risk factors for adiposity is unclear.

Objective: The objective was to examine the association of greater maternal weight gain (MWG; postnatal weight minus weight at the first antenatal clinic assessment) with greater offspring BMI and to explore whether any observed association is explained by intrauterine mechanisms.

Design: This was a prospective cohort study that used record linkage data (n = 146,894 individuals from 136,050 families). To compare the within-sibling and between-nonsibling associations, we used fixed- and between-cluster linear regression models.

Results: Associations of MWG with later offspring BMI differed by the mother's early-pregnancy overweight or obesity status (P for interaction <0.0001). MWG was positively associated with BMI at a mean age of 18 y in the offspring of normal-weight women but only between unrelated men (0.07; 95% CI: 0.06, 0.07) per 1-kg greater MWG; no within-sibling association (0.00; 95% CI: -0.02, 0.02) per 1-kg greater MWG was found. In contrast, in overweight and obese women we found a within-sibling association (0.06; 95% CI: 0.01, 0.12) and an association between unrelated men (0.02; 95% CI: 0.01, 0.03) per 1-kg greater MWG.

Conclusion: In normal-weight mothers, most of the association between MWG and later offspring BMI is explained by shared familial (genetic and early environmental) characteristics, whereas evidence indicates a contribution of intrauterine mechanisms in overweight and obese women.