Thyroid antibodies and fetal loss: an evolving story

This article reviews the literature on thyroid antibodies and miscarriage. In 1990, in a study designed to determine the incidence and etiology of postpartum thyroiditis, a serendipitous finding emerged revealing an association between thyroid antibodies and spontaneous miscarriage. Subsequently, four other studies, performed on three different continents, have confirmed the correlation. Six studies have evaluated the relationship between thyroid antibodies and recurrent abortion, defined as three or more spontaneous miscarriages. The majority of the studies (67%) reported a statistically significant increase in the incidence of thyroid antibodies in the recurrent abortion group as compared to controls. Four intervention trials have evaluated the impact of immunosuppressive therapy in women with thyroid antibodies. Although all of the trials revealed a decrease in the incidence of recurrent abortion, each study was limited by methodological concerns. A recently developed murine model of pregnancy has also demonstrated increased fetal loss in female mice immunized with thyroglobulin when mated with allogeneic males. The implications of these data generated over the last decade are discussed.