Autoimmune Thyroid Disease in Pregnancy and the Postpartum Period: Relationship to Spontaneous Abortion

Abstract

The aim of this study was to determine the prevalence of autoimmune thyroid disease and the risk of miscarriage in autoimmune thyroid antibody (ATA)-positive women. Eight hundred seventy-six subjects completed the study, and 12.3% were thyroid antibody-positive (4.5% tested positive for both thyroid peroxidase antibody [TPO-Ab] and thyroglobulin autoantibody [Tg-Ab], 4.79% were TPO-Ab-positive only, and 3.1% were Tg-Ab-positive only). Fifty percent of the ATA-positive women and 14.1% of the ATA-negative group had a history of spontaneous abortion. Forty-eight of the ATA-positive women developed postpartum autoimmune thyroid dysfunction (PATD). Of these, 50% had hypothyroidism alone, 31.3% had transient hyperthyroidism followed by hypothyroidism, and 18.8% had transient thyrotoxicosis alone. Of the 48 PATD subjects, 12.5% developed persistent hypothyroidism. None of the ATA-negative women developed any form of thyroid dysfunction. The thyroid-stimulating hormone (TSH) levels in the ATA-positive group were significantly higher than those in the ATA-negative group, and only the ATA-positive women with a history of abortion had significantly higher TSH and lower free thyroxine (FT₄) concentrations than the other subgroups. The results revealed a 5.5% prevalence rate for PATD in the study population. In addition to TPO-Ab, Tg-Ab is a useful marker for autoimmune thyroiditis.