Aims: To examine the association between thyroid autoimmunity (TAI) and early pregnancy serum beta human chorionic gonadotropin (ß-hCG) levels in spontaneous pregnancy. Methods: In this retrospective case-control study, women between the ages of 20 and 40 were included. The study subjects were 130 women euthyroid and healthy patients with spontaneous pregnancy. Subjects were divided into two groups: those with autoimmune thyroid disease (TAI group; n=60) and those without the disease (control group; n=70). Results: The mean age and body mass index (BMI) of the subjects were 30.22±4.14 years and 24.51±2.04, respectively. The value of anti-thyroid peroxidase antibodies (TPO-Abs) and anti-thyroglobulin antibodies (TG-Abs) in the TAI group is three times twenty times more than the control, respectively. Results found no statistically significant association between between TAI and control groups in regard to hemoglobin, alanine transaminase (ALT), aspartate transaminase (AST), thyroid-stimulating hormone (TSH), platelet (PLT), creatine, free thyroxin (FT4), and blood urea nitrogen (BUN) (p>0.05). There was statistically significant difference between groups in terms of the serum ß-hCG level (p<0.05). Conclusion: In this study, the effects of TAI were significant on early-stage pregnancy serum ß-hCG levels; therefore, thyroid levels should be considered, and proper treatment should be started early.