Impact of thyroid autoimmunity on pregnancy outcomes in euthyroid patients with recurrent implantation failure

Research question: Does thyroid autoimmunity (TAI) adversely affect pregnancy outcomes after IVF/intracytoplasmic sperm injection (ICSI) in euthyroid patients with recurrent implantation failure (RIF)? Design: This retrospective cohort study was conducted at the Reproductive Hospital Affiliated with Shandong University from November 2016 to September 2021. A total of 1031 euthyroid patients diagnosed with RIF were enrolled. Based on serum thyroid autoantibody concentrations, the participants were divided into two groups: the TAI-positive group (219 women with RIF) and the TAI-negative group (812 women with RIF). The parameters were compared between the two groups. Additionally, logistic regression was used to adjust related confounders for primary outcomes, and subgroup and stratified analyses were performed according to different thyroid autoantibody types and TSH concentrations. Results: There was no significant difference in ovarian reserve, ovarian response, embryo quality, pregnancy outcome or neonatal outcome between the two groups (P > 0.05). After adjustments for age, body mass index, thyroid-stimulating hormone and free thyroxine, the biochemical pregnancy rate in the TAI-positive group was significantly lower than that in the TAI-negative group (odds ratio 1.394, 95% CI 1.023-1.901, adjusted P = 0.036). Regarding the implantation rate, clinical pregnancy rate, pregnancy loss rate, stillbirth rate and live birth rate, no significant differences were observed even with subgroup and stratified analyses (P > 0.05). Conclusions: TAI had no impact on pregnancy outcomes in euthyroid RIF patients who underwent IVF/ICSI. In clinical practice, interventions targeting thyroid autoantibodies in these patients should be implemented with caution and additional evidence is needed.