Maternal BMI, gestational diabetes, and weight gain in relation to childhood obesity: The mediation effect of placental weight.

Objective: High prepregnancy body mass index (BMI), excessive gestational weight gain (GWG), and gestational diabetes mellitus (GDM) are associated with the risk of childhood obesity. This study aims to examine the extent to which these effects may be mediated through the placenta.
Methods: Data included 33,893 mothers and their singleton infants from birth to 7 years old (total 154,590 visits) in the Collaborative Perinatal Project, a U.S. multicenter prospective cohort study from 1959 to 1976. The placentas were weighed after removing cord and membranes. We performed sequential generalized estimating equation-linear models excluding and including placental weight to evaluate its mediation effect.
Results: In this population, 21.7% of mothers had overweight or obesity, 17.3% had excessive GWG, and 350 (1%) had diagnosed GDM; in addition, 7.2% children had obesity. After adjustment for prepregnancy BMI and other covariates, childhood BMI was 0.23 (95% CI: 0.05, 0.40) kg/m(2) higher for children born to mothers with GDM versus those without GDM. Inclusion of placental weight in the model attenuated the association by 52% to 0.11 (95% CI: -0.06, 0.28) and similarly attenuated the associations with childhood BMI for GWG by 25% and maternal prepregnancy BMI by 17%.
Conclusions: Placental weight partly mediates the effects of prepregnancy BMI, excessive GWG, and GDM on childhood BMI.
(© 2016 The Obesity Society.)