Because subclinical hypothyroidism (thyroid-stimulating hormone [TSH] > 4.5 IU/mL) is associated with adverse pregnancy outcome, including early pregnancy loss, TSH is recommended to be titrated to ≤2.5 mIU/L in levothyroxine-treated women before pregnancy. The purpose of this study was to determine whether borderline-subclinical hypothyroidism (borderline-SCH; 2.5 < TSH ≤ 4.5 IU/mL) affects the outcome of subsequent pregnancies in women with unexplained recurrent pregnancy loss (uRPL).