Abstract
Background: Thyroid autoimmunity (TAI) has been widely associated with reduced fertility; however, its impact on assisted reproductive technology (ART) outcomes in euthyroid women remains controversial. Ovarian reserve (OR) and anti-Müllerian hormone (AMH) are considered to be the most reliable predictors of controlled ovarian hyperstimulation (COH) and ART outcome. This study aims to evaluate whether TAI affects COH outcomes depending on the OR, or if TAI is an independent negative factor affecting COH outcomes. Methods: This study includes 341 infertile euthyroid participants under 38 years old undergoing ART at a single reproductive medicine center. The serum concentrations of sex hormones, thyrotropin (TSH), AMH, and antithyroid antibodies (ATAbs) were measured before COH. Ovarian response to COH, assessed by oocyte number and maturation (percentage of mature MII oocytes), fertilization rate (FR), and early embryo development (cleavage and blastocyst rate), were assessed in 191 participants with TAI and 150 TAI negative age-matched controls with normal ORs. The TAI group was further divided into two subgroups: the TAI1 group with normal OR (n = 120) and the TAI2 group with diminished ORs (n = 71). Results: The mean of the retrieved oocytes was significantly lower in TAI1 (p = 0.015) and expectedly significantly lower in TAI2 (p < 0.001) compared to the control. The percentage of MII oocytes was significantly lower in the TAI1 (p < 0.001) and TAI2 (p = 0.009) groups compared to the control group. We observed significantly lower FR (p = 0.002), cleavage rate (p = 0.020), and blastocyst rate (p < 0.001) in the TAI1 group compared to control. In the TAI2 group, there was a lower cleavage rate (p < 0.001) and blastocyst rate (p < 0.001) compared to the control. There was no difference in the mean percentage of MII oocytes, FR, and cleavage rate between the TAI1 and TAI2 groups, but the blastocyst rate was significantly lower (p < 0.001) in the TAI2 group. Conclusions: TAI may represent a negative predictor of in vitro fertilization outcomes by impairing oocyte maturation, fertilization rate, and embryo development in ART cycles, regardless of ORs.