485 Association Between Perinatal Phthalate Metabolite Concentrations and Postpartum Glucose Levels: a Prospective Observational Study

To study the associations of pregnancy and postpartum exposure to phthalates, a class of endocrine disrupting chemicals, with postpartum glucose tolerance. Pregnant participants in the Environmental Reproductive and Glucose Outcomes Study with data on urinary phthalate metabolite concentrations at ≤ 4 study visits (median 11 [Visit 1, V1], 19 [Visit 2, V2], and 26 [Visit 3, V3] weeks’ gestation and median 7 weeks postpartum [PP]) and available PP fasting and 2-hour glucose levels after a 75-gram oral glucose tolerance test were included. Phthalate metabolite concentrations (e.g. MCOCH, MHiNCH, MBP, etc.) were specific-gravity adjusted and modeled individually and as mixtures at each timepoint. Analyses were adjusted for age, pre-pregnancy BMI, education, and parity. 201 participants were included [mean(SD) age: 33 (5) years; fasting glucose: 82 (8) mg/dL; 2-hour glucose: 88 (22) mg/dL] with phthalate data measures available for 90%, 81%, 86% and 92% at V1, V2, V3 and PP, respectively. V1 MCOCH and MHiNCH; V2 MBP; and PP MEHHP, MEHP, MHBP were associated with higher fasting glucose levels, while V2 MCNP was associated with higher 2-hour postprandial glucose levels. MEHHTP at V2 and MCOP at V3 were associated with lower fasting glucose levels. V1 MECPTP and MEHHTP; V2 MBP, MBzP, MEHHP, MEOHP; V3 MEHHP and MHiNCH; and PP MCPP and MHiBP were associated with lower 2-hour postprandial glucose levels. Weighted quantile sum regression identified pregnancy MCOCH (positive direction) and MEP (negative direction) in the phthalate mixture as important contributors to the mixture’s associations with PP fasting and 2-hour glucose levels. In our cohort, pregnancy and postpartum urinary phthalate metabolite concentrations were associated with altered glucose metabolism in the postpartum period, although findings varied by timing of phthalate measurement. Given the ubiquitous nature of phthalates in consumer products, it is important to further explore the influence of phthalate metabolites concentrations on PP glucose metabolism.