Objective:

To explore the gestational dynamics of maternal thyroid hormones and their associations with neonatal birth outcomes.

Key Findings:

• Maternal TSH levels increased gradually, while TT3 peaked in mid-pregnancy and FT3/FT4 levels declined continuously.
• Correlations between maternal thyroid hormones and neonatal outcomes were noted, with trimester- and sex-specific associations for TT4, TT3, FT3, and FT4 with birth weight, length, and parity.
• Dose-response relationships were identified with pregnancy stage and sex-specific patterns.
• Positive correlations of thyroid hormone mixtures with neonatal outcomes were noted in early/mid-pregnancy, with significant correlations in late pregnancy.

Interpretation:

The findings highlight the complexity of thyroid hormone dynamics and their associations with neonatal outcomes across different trimesters and infant sexes.

Limitations:

• The specific plan and quality control measures for thyroid hormone testing were not documented.
• The study population may not be representative of all pregnant women due to specific inclusion and exclusion criteria.

Conclusion:

The study underscores the need for gestational thyroid function monitoring to inform maternal–infant health strategies.