Abstract
BACKGROUND: Unexplained recurrent pregnancy loss (URPL) and thyroid autoimmunity (TAI) have received considerable attention. However, the association between TAI and subsequent infertility or pregnancy outcomes among euthyroid women with URPL remains unclear. This study aimed to clarify these relationships. METHODS: From September 2019 to December 2022, we prospectively enrolled women with URPL at the Lanzhou University Second Hospital and collected pre-pregnancy and first-trimester data. Participants were divided into two groups: TAI and non-TAI, based on their thyroid antibody status. Changes in thyroid function parameters from pre-pregnancy to the first trimester were compared between the two groups. We assessed the incidence of infertility, subsequent pregnancy loss, and pregnancy complications. Logistic regression analysis was performed to examine the associations between TAI and infertility, subsequent pregnancy loss, and adverse pregnancy outcomes, after adjusting for maternal age, body mass index, gravidity, number of pregnancy losses, and concentrations of thyroid-stimulating hormone (TSH) and free thyroxine (fT4). RESULTS: Of the 576 euthyroid women with URPL included, 101 (17.5%) were classified as TAI, and 475 (82.5%) as non-TAI. Subsequently, 110 (19.1%) patients were diagnosed with infertility and 466 (80.9%) patients conceived. The mean TSH concentrations in the TAI group were higher than those in the non-TAI group both pre-pregnancy (2.3 ± 0.8 vs. 2.2 ± 0.9 mIU/L, P = 0.085) and in the first trimester (2.1 ± 1.2 vs. 1.7 ± 0.9 mIU/L, P = 0.014). The mean fT4 concentration in the first trimester was lower in the TAI group (14.2 ± 2.8 vs. 14.9 ± 1.9 ng/ml, P = 0.024). Logistic regression analysis showed that TAI was independently associated with increased risks of subsequent pregnancy loss (OR 2.953, 95%CI 1.142-3.693), hypothyroidism during pregnancy (OR 5.567, 95%CI 3.035-10.210), premature rupture of membranes (OR 2.198, 95%CI 1.051-4.595), and preterm birth (OR 2.865, 95%CI 1.132-7.249). CONCLUSIONS: Among euthyroid women with URPL, TAI is independently associated with increased risks of subsequent pregnancy loss, hypothyroidism during pregnancy, premature rupture of membranes, and preterm birth, underscoring the need for pre-pregnancy attention.