Reduced thyroid function during pregnancy can have adverse effects on both the mother and fetus, including increased risk of miscarriage and preterm labor. Thyroid autoimmunity also puts the mother at increased risk of developing postpartum thyroiditis and hypothyroidism in the future. While screening of high-risk women for thyroid dysfunction is recommended, universal screening of pregnant women remains controversial.
Chrysoula Dosiou, MD, of Stanford University School of Medicine, and colleagues from the University of Illinois at Chicago, V. Fazzi Hospital in Lecce, Italy, Stanford University School of Medicine in Stanford, California, and George Washington University School of Medicine and Health Sciences Washington, D.C., developed a computer model to compare the cost-effectiveness of three screening strategies: universal screening with thyroid-stimulating hormone and anti-thyroid peroxidase antibodies during the first trimester, risk-based screening, and no screening. In this model, a positive screening test led to follow-up testing and treatment with thyroid hormone when indicated. The model takes into account the development of adverse obstetrical outcomes during pregnancy, postpartum thyroiditis, and overt hypothyroidism during a woman’s lifetime.
According to data presented today at the 81st Annual Meeting of the American Thyroid Association (ATA), universal screening for autoimmune thyroid disease in the first trimester of pregnancy is cost-effective compared with screening of only high-risk women. Both the risk-based and universal screening options are cost-effective when relative to no screening.
About the ATA Annual Meeting
The 81st Annual Meeting of the American Thyroid Association will be held October 26-30, 2011 at the Renaissance Esmeralda Resort & Spa in Indian Wells (near Palm Springs), California. This four day creative and innovative scientific program, chaired by Drs. Anthony Hollenberg and Martha Zeiger, has carefully balanced clinical and basic science sessions on the latest advances in thyroidology. The ATA meeting is designed to offer continuing education for endocrinologists, internists, surgeons, basic scientists, nuclear medicine scientists, pathologists, endocrine fellows and nurses, physician assistants and other health care professionals.
Autoimmune Thyroid Disease and Pregnancy
Thyroid disorders are the second most common endocrinologic disorders found in pregnancy. Overt hypothyroidism is estimated to occur in 0.3-0.5% of pregnancies. Subclinical hypothyroidism appears to occur in 2-3%, and hyperthyroidism is present in 0.1-0.4%.
Autoimmune thyroid dysfunctions remain a common cause of both hyperthyroidism and hypothyroidism in pregnant women. Graves disease accounts for more than 85% of all cases of hyperthyroid, whereas Hashimoto thyroiditis is the most common cause of hypothyroidism.
Postpartum thyroiditis (PPT) reportedly affects 4-10% of women. PPT is an autoimmune thyroid disease that occurs during the first year after delivery. Women with PPT present with transient thyrotoxicosis, hypothyroidism, or transient thyrotoxicosis followed by hypothyroidism. This presentation may be unrecognized, but is important because it predisposes the woman to develop permanent hypothyroidism.
Of interest, symptoms of autoimmune thyroid diseases tend to improve during pregnancy. A postpartum exacerbation is not uncommon and perhaps occurs because of an alteration in the maternal immune system during pregnancy. The improvement in thyroid autoimmune diseases is thought to be due to the altered immune status in pregnancy.
Author: Dotun A Ogunyemi, MD; Chief Editor: Carl V Smith, MD
About the ATA
The American Thyroid Association (ATA) is the leading worldwide organization dedicated to the advancement, understanding, prevention, diagnosis and treatment of thyroid disorders and thyroid cancer. ATA is an international individual membership organization with over 1,400 members from 43 countries around the world. Celebrating its 88th anniversary, ATA delivers its mission through several key endeavors: the publication of highly regarded monthly journals, THYROID, Clinical Thyroidology and Clinical Thyroidology for Patients; annual scientific meetings; biennial clinical and research symposia; research grant programs for young investigators, support of online professional, public and patient educational programs; and the development of guidelines for clinical management of thyroid disease.
Uncontrolled hyperthyroidism, especially in the second half of pregnancy, can lead to numerous complications. Maternal complications include miscarriage, infection, preeclampsia, preterm delivery, congestive heart failure (CHF), thyroid storm, and placental abruption. Fetal and neonatal complications include prematurity, small size for gestational age, intrauterine fetal death, and fetal or neonatal goiter and/or thyrotoxicosis. Overtreatment may cause iatrogenic fetal hypothyroidism.
Maternal complications of untreated hypothyroidism include microcytic anemia, preeclampsia, placental abruption, postpartum hemorrhage, cardiac dysfunction, and miscarriage. Fetal or neonatal complications include prematurity, low birth weight, congenital anomalies, stillbirth, and poor neuropsychological development.
In particular, overt maternal hypothyroidism is associated with neonatal neurologic developmental delay because of the transplacental transfer of thyroid hormone in early pregnancy is inadequate. This process is required for brain development. The fetal thyroid does not begin to concentrate iodine until 10-12 weeks of gestation. Therefore, before this time, the mother must provide for all of the fetus’ thyroxine (T4) requirements.
Approximately 10-15% of the population has thyroid antibodies. These antibodies have been linked to an increased risk of spontaneous abortion.
Subclinical hypothyroidism also has been associated with spontaneous abortion and with preterm labor.
Source: American Thyroid Association