Objective To investigate the effects of exposure to per-/polyfluoroalkyl substances (PFASs) in umbilical cord blood on the levels of thyroid stimulating hormone (TSH) in neonates.

Methods A total of 1 015 pairs of mothers and infants who joined the Healthy Baby Cohort in Wuhan, China from 2013 to 2014 were enrolled as subjects. UPLC-MS/MS was used to measure the concentrations of 13 homologs of PFASs in neonatal umbilical cord blood samples. The data on TSH concentrations in neonates' heel blood samples were obtained from the neonatal disease screening report. Multiple linear regression model and the weighted quantile sum (WQS) regression model were used to assess the effects of single and mixed exposure to PFASs in mothers during pregnancy on the concentration of TSH in neonates.

Results Of 1 015 umbilical cord blood samples, 9 homologs of PFASs showed a detection rate of more than 95%, among which perfluorooctanoic acid(PFOA) and perfluorooctane sulfonate(PFOS) had the relatively high concentrations, with a median concentration of 1.60 and 4.04 ng/mL, respectively. The median concentration of TSH was 3.24 μIU/mL. The results from multiple linear regression analysis showed that for every 1 ng/mL increase in perfluorobutane sulfonate (PFBS) exposure concentration, the concentration of TSH in neonates was reduced by 15.82% (ΔTSH% = -15.82%, 95% confidence interval CI: -24.39% to -6.27%, P < 0.01). The stratified analysis based on the genders of neonates showed that for every 1 ng/mL increase in the exposure concentration of PFBS and 8∶2 chlorinated polyfluorinated ether sulfonate (8∶2 CI-PFESA), the concentration of TSH in boys was decreased by 24.93% (ΔTSH% = -24.93%, 95% CI: -35.87% to -12.13%, P < 0.01) and 18.63% (ΔTSH% = -18.63%, 95% CI: -32.70% to -1.62%, P < 0.05), respectively, while there was no significant change in the concentration of TSH in girls. Otherwise, no statistically significant association was found between exposure to the other PFASs and TSH levels in both boys and girls. The WQS regression analysis showed that for every 1 ng/mL increase in the exposure concentration of the mixture of 11 homologs of PFASs, the concentration of TSH in neonates was reduced by 34.30% (ΔTSH% = -34.30%, 95% CI: -54.36% to -5.41%, P < 0.05), and among these PFASs, PFBS and 8∶2 CI-PFESA had the greatest contribution to combined exposure effect, with a weight of 49.40% and 37.60%, respectively.

Conclusion Higher PFBS and 8∶2 CI-PFESA exposure in cord sera were negatively associated with neonatal TSH concentration, and those associations were more significant in boys than girls.