Background Maternal thyroid hormones have been shown to affect neonatal thyroid function. However, it remains unclear whether these associations persist across trimesters, and also little knows regarding the potential effects of mixtures. Objective This study aimed to examine the effects of maternal thyroid hormones as individual and mixtures across three trimesters on neonatal thyroid stimulating hormone (TSH). Methods We included 2,139 pregnant women. Maternal thyroid hormonesTSH, free triiodothyronine (FT3), and free thyroxine (FT4) across three trimesters and neonatal TSH level were measured. Multivariable linear regression models and Bayesian kernel machine regression (BKMR) models were used to examine the associations between maternal thyroid hormones (individual and mixtures) across three trimesters and neonatal TSH. Results Maternal TSH demonstrated the positive associations with neonatal TSH across three trimesters (first trimester:β = 0.112; 95% CI: 0.008, 0.215; second trimester:β = 0.122; 95% CI: 0.032, 0.212; third trimester:β = 0.115; 95% CI: 0.031, 0.200). Neonatal TSH was also positively associated with maternal FT4 in the third trimester (β = 1.313; 95% CI: 0.367, 2.239). Moreover, we found sex-specific associations, and the positive associations of maternal TSH and FT4 with neonatal TSH in the third trimester were observed only among female infants, while the positive association of maternal TSH with neonatal TSH in the second trimester was observed only among male infants. The overall positive associations of the mixtures were observed, and maternal TSH was identified as the major contributors. Conclusion Maternal thyroid hormones affect neonatal thyroid function across all three trimesters by fetal sex.
Zhou et al. (Mon,) studied this question.