Prenatal Phthalates, Gestational Weight Gain, and Long-term Weight Changes Among Mexican Women

Background: Phthalates are endocrine disrupting chemicals that may influence weight status; however, few studies have considered weight gain during pregnancy and subsequent long-term weight changes in women.

Objective: To determine associations of prenatal phthalate exposure with maternal weight during pregnancy and through up to seven years post-delivery.

Methods: We analyzed 15 urinary phthalate biomarker concentrations during the 2nd and 3rd trimesters among 874 pregnant women enrolled in the Programming Research in Obesity, Growth Environment and Social Stress Study in Mexico City. We examined three time-specific maternal weight outcomes: gestational weight gain (between 2nd and 3rd trimesters), short-term weight (between 3rd trimester and 12 months post-delivery), and long-term weight (between 18 months and 6-7 years post-delivery). We used Bayesian Kernel Machine Regression (BKMR) to estimate associations for the total phthalate mixture, as well as multivariable linear mixed models for individual phthalate biomarkers.

Results: As a mixture, 2nd trimester urinary phthalate biomarker concentrations were associated with somewhat lower gestational weight gain between the 2nd and 3rd trimesters (interquartile range, IQR, difference: -0.07 standard deviations, SD; 95% credible interval, CrI: -0.20, 0.06); multivariable regression and BKMR models indicated that this inverse association was primarily driven by mono-2-ethyl-5-carboxypentyl terephthalate (MECPTP). Prenatal (2nd and 3rd trimesters) urinary phthalate mixture concentrations were positively associated with maternal weight change through 12 months postpartum (IQR difference: 0.11 SD; 95% CrI: 0.00, 0.23); these associations persisted from 18 months to 6-7 years follow-up (IQR difference: 0.07 SD; 95% CrI: 0.04, 0.10). Postpartum weight changes were associated with mono-3-carboxypropyl phthalate (MCPP) and MECPTP.

Conclusions: Prenatal phthalate exposure was inversely associated with gestational weight gain and positively associated with long-term changes in maternal weight. Further investigation is required to understand how phthalates may influence body composition and whether they contribute to the development of obesity and other cardiometabolic diseases in women.