LAUSR

Key Points Question Are abnormal preconception thyrotropin levels associated with adverse maternal and fetal outcomes? Findings In this populational-based cohort study of over 5.8 million Chinese women, both low and high maternal preconception thyrotropin levels were associated with higher risk of preterm birth, small for gestational age, and perinatal infant death. Meaning In this study, both low and high maternal thyrotropin levels were associated with a significantly increased risk of adverse pregnancy outcomes; the optimal preconception thyrotropin levels may be between 0.37 mIU/L and 2.50 mIU/L.