Exposure to organophosphate esters and trajectories of gestational weight gain: A large prospective cohort study

Organophosphate esters (OPEs) can be used as flame retardants and plasticizers in consumer products. Gestational exposure may disrupt maternal metabolic function, which is dynamic during pregnancy. Gestational weight gain (GWG) serves as an important indicator of maternal metabolic health. We aimed to determine prospective associations between biomarkers of maternal OPE exposure and GWG.

Concentrations of five OPE biomarkers were measured across repeated urine samples in the LIFECODES Fetal Growth Study (n = 901, 2008-2018) and evaluated as pregnancy-averaged values. Maternal weight gain was calculated from repeated weight measures (median = 14/participant) and mixed-effects modeling was applied to predict maternal weight at delivery. Total GWG, the primary outcome, was calculated by the difference between predicted weight at delivery and self-reported pre-pregnancy weight. Linear regression models estimated associations between individual biomarkers and total GWG. Group-based trajectory models were used to identify three trajectories of GWG (i.e., low-catch up, expected, constant-high), and associations between OPEs and trajectory membership were estimated using multinomial regression models.

We observed mixed associations between OPE biomarkers and GWG. For example, a doubling in bis(2-chloroethyl) phosphate was associated with 0.14 kg lower (95% confidence interval [CI]: -0.26, 0.01) GWG, whereas a doubling in diphenyl phosphate (DPHP) was associated with 0.16 kg greater (95% CI: -0.08, 0.46) GWG; however, both confidence intervals included the null. Among GWG trajectories, a doubling in DPHP was associated with higher odds of being in the constant-high GWG trajectory (early rapid, sustained weight gain) compared to the expected group (odds ratio: 1.28, 95% CI: 0.98, 1.69).

This study provides novel evidence that certain OPE exposures may not only influence women's total weight gain during pregnancy, but the trajectory in which that weight gain occurs.