Background: Preterm birth (PTB, < 37 completed weeks' gestation) is one of the global public health concerns. Epidemiologic evidence on the potential impact of perfluoroalkyl substances (PFAS) on PTB is still limited and inconsistent. We aimed to investigate the associations between prenatal PFAS exposure and PTB among singleton live births.Methods: We studied 2849 mother-infant pairs in the Shanghai Birth Cohort (SBC) from 2013 to 2016. Ten PFAS in maternal plasma in early pregnancy

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... l age, median (interquartile range): 15 (13 - 16) weeks) were measured. Primary outcomes were duration of gestation, PTB, spontaneous PTB and clinically indicated PTB. A linear regression model was used to assess the associations between ln-transformed PFAS and duration of gestation (in weeks). Logistic regression models were applied to estimate the relative risks of these outcomes. Results: The incidence of overall PTB was 4.8% (95% confidence limit: 4.0% - 5.6%, n = 136) in this study population. In the linear regression analyses, PFAS were not associated with the duration of gestation after controlling for potential confounders. In the multiple logistic models, no significant associations were observed between PFAS and overall PTB, spontaneous or indicated PTB. Conclusion: Our prospective cohort study shows that maternal plasma PFAS concentrations in early pregnancy was not associated with gestational length, overall PTB, spontaneous or indicated PTB.