Thyroid dysfunction is a condition known to reduce the likelihood of pregnancy and can also adversely affect pregnancy. Positive thyroid antibodies, even in the presence of normal thyroid function, increase the risk of miscarriage two or three times, even in spontaneous pregnancies. Now new research published in The Journal of Clinical Endocrinology & Metabolism indicates that women who test positive for thyroid antibodies prior to receiving fertility treatment may be at an increased risk for miscarriage. The study emphasizes the importance of testing thyroid autoimmunity prior to assisted reproduction therapies in women.

      Research has shown that women who suffer from infertility are at an increased risk for associated thyroid autoimmunity compared with age-matched fertile women. While most infertile couples use assisted reproduction technologies to become pregnant, such as in vitro fertilization, 20 to 30 percent of these pregnancies are complicated by miscarriage.

      Dr. Kris Poppe and researchers at the Vrije Universiteit Brussel, in Belgium, sought to determine whether the presence of positive thyroid antibodies influences the rate of miscarriage in infertile women. They conducted a prospective analysis on 234 infertile women between the ages of 20 and 50 years who visited the Center for Reproductive Medicine, in Belgium. The women were screened for thyroid peroxidase antibodies (TPO-Ab), thyroid stimulating hormone (TSH), and free T4 before undergoing assisted reproduction. The endpoints of the assisted reproduction were pregnancy, miscarriage, or birth.

      The researchers found positive thyroid antibodies in about 14 percent of the subjects. Approximately 53 percent of these women became pregnant. Yet the miscarriage rate for these women was more than 50 percent, compared with only 23 percent in the women negative for thyroid antibodies, despite comparable thyroid function prior to the procedure. The women in both groups were age-matched.

      "These findings help conclude that thyroid antibodies could be assessed in women before they undergo assisted reproduction therapies," noted Dr. Poppe, the first author of the study. "This test could help determine the risk for miscarriage. Larger studies are now needed to confirm these findings."

Source: The Endocrine Society, Sept 9, 2003