Phthalate Exposure in Relation to Maternal Thyroid and Reproductive Hormone Levels during Pregnancy

There is increasing evidence that exposure to phthalates during pregnancy may elevate the risk of adverse reproductive outcomes such as preterm birth. Maternal endocrine disruption across pregnancy may be one pathway mediating some of these relationships. We investigated whether urinary phthalate metabolites were associated with maternal thyroid (thyroid-stimulating hormone [TSH], free thyroxine [FT4], and free triiodothyronine [FT3]) and reproductive (sex hormone-binding globulin [SHBG], progesterone, and estradiol) hormone levels at multiple time points during pregnancy. Preliminary data (n=106) were obtained from an ongoing prospective birth cohort in Northern Puerto Rico. We measured 11 urinary phthalate metabolite concentrations in urine samples collected up to three visits per subject during pregnancy (18±2, 22±2, and 26±2 weeks of gestation; N=293 total samples). We also measured thyroid and reproductive hormone concentrations in serum collected at up to two time points per subject during pregnancy...