Objective: Autoimmune thyroid disease (AITD) has been associated with adverse pregnancy outcomes in subfertile women with spontaneous and assisted reproductive technology-induced pregnancies. The underlying pathophysiology is still elusive and an association with thyroid dysfunction or other infertility causes is discussed. However, whether thyroid autoimmunity (TAI) per se has a negative impact on female fertility has not yet been clarified. In this study, we investigated whether TAI in healthy women undergoing intracytoplasmic sperm injection (ICSI) for male infertility may affect pregnancy outcome. Design: A retrospective, single-centre study. Methods: The ICSI outcome data obtained from 835 euthyroid women (age: 31.4G4.3 years, BMI: 23.7G4.2 kg/m 2 ) were correlated with pre-ICSI TAI status. The known causes of female subfertility were excluded. Outcome parameters included rates of pregnancy, birth, miscarriage and preterm delivery. Blood analysis was carried out retrospectively using blood samples drawn before ICSI. TAI was defined by elevation of anti-thyroperoxidase-or anti-thyroglobulin-antibodies O100 U/l. Results: TAI-positive and -negative groups did not differ in age, BMI or TSH levels. TAI status did not influence any ICSI outcome parameters. In contrast, increasing maternal age was significantly correlated with lower pregnancy rate (odds ratio (OR): 0.94 (95% CI: 0.91-0.97); PZ0.0003) and birth rate (OR: 0.93 (95% CI: 0.09-0.97); P!0.0001). Conclusions: Our study suggests that TAI per se does not influence ICSI outcome. A strict definition of AITD and TAI and consideration of TAI-associated and -independent confounders are important to further elucidate the interplay between TAI and reproduction.