Influence of thyroid autoimmunity at various clinical stages of hypothyroidism on the risk of miscarriage before 20 weeks of gestation

Purpose We aimed to clarify the influence of thyroid autoantibodies at various clinical stages of hypothyroidism on the risk of pregnancy loss before 20 weeks of gestation. Methods We enrolled 230 pregnant women with a history of recurrent miscarriage. Detailed clinical history, physical examination, and laboratory testing of thyroid function, antithyroid peroxidase (anti-TPO), and antithyroglobulin (anti-TG) were applied among all participants. Results Coexisting overt hypothyroidism and positive thyroid autoantibodies quadrupled the risk of miscarriage in women before 20 weeks of gestation (OR 4.04, 95% CI = 2.08–7.96, P < 0.001). Women with subclinical hypothyroidism (OR 1.44, 95% CI = 0.81–2.57, P = 0.132,) or who were euthyroid (OR 1.53, 95% CI = 0.86–2.73, P = 0.094) showed a non-significant risk of miscarriage even with positive thyroid autoantibodies. Thyroid-stimulating hormone (TSH) was positively correlated with the number of miscarriages rather than anti-TPO ( P < 0.001 and 0.209, respectively). Conclusion Coexistence of overt hypothyroidism and thyroid autoimmunity was the only significant driver of pregnancy loss before 20 weeks of gestation.