Bisphenol A and bisphenol S exposures during pregnancy and gestational age - A longitudinal study in China.

Bisphenol A (BPA) and its substitute bisphenol S (BPS) are endocrine-disrupting chemicals and metabolized rapidly in human body. BPA exposure in late pregnancy has been suggested to be associated with preterm birth (PTB), but the associations of trimester BPA and BPS exposures with gestational age have been rarely studied. We aimed to examine maternal urinary BPA and BPS levels longitudinally measured across pregnancy in relation to gestational age and PTB. A prenatal cohort study was conducted between 2014 and 2015 in Wuhan, China. Maternal urinary BPA and BPS concentrations were measured in a complete series of urine samples collected in the 1st, 2nd and 3rd trimesters from 850 pregnant women and corrected by specific gravity. In comparison with the lowest tertile of maternal urinary BPA, higher levels of averaged BPA concentration across pregnancy was associated with a 1.97-day decrease in gestation (95% CI: 3.25, -0.68) and an adjusted odds ratio of 3.19 (95% CI: 1.00, 10.45) for PTB. Higher BPA concentrations in three trimesters were also negatively associated with gestational age and positively correlated with PTB. In contrast, only a positive association of third-trimester BPS with gestational age was found, but the significant association disappeared in the adjusted models. Both maternal trimester and averaged BPA exposure across pregnancy were significantly associated with shortened gestation and increased risk of PTB. However, the results showed little evidence of a relationship between BPS and PTB.