Gestational exposure to organophosphate ester flame retardants and risk of childhood obesity in the environmental influences on child health outcomes consortium

•Prenatal OPE exposure and childhood obesity risk in the diverse ECHO cohort.•DBUP/DIBP associated with increased middle childhood obesity risk.•BDCPP associated with reduced middle childhood obesity risk.•No significant associations found for DPHP, BCPP, BBOEP, and BCETP.•Bayesian mixture analysis supports findings from regression models. Introduction: Organophosphate esters (OPEs) are increasing in use as flame retardants and plasticizers and concerns have been raised given their endocrine-disrupting activities and possible obesogenic consequences. However, longitudinal studies on gestational OPE exposure and childhood obesity are scarce. This study examined whether OPE levels in maternal urine during pregnancy were associated with the risk of childhood obesity. Methods: OPEs were analyzed in pregnancy urine samples of 5,087 individuals from 14 studies contributing to the Environmental influences on Child Health Outcomes (ECHO) Cohort. BDCPP, DBUP/DIBP, and DPHP, detected in > 80 % of the samples, were modeled continuously and by tertiles; whereas BCPP, BBOEP, and BCETP, detected in 50–80 % of samples, were modeled categorically (not-detected, low, and high). Childhood obesity was defined by BMI z-score ≥ 95th percentile according to WHO (