Thyroid insufficiency during pregnancy: complications and implications for screening

In 2007, clinical practice guidelines concerning the management of thyroid dysfunction during pregnancy and postpartum were published in the Journal of Clinical Endocrinology and Metabolism. They were elaborated on by a panel of experts, representative of the Latin American Thyroid Society, the Asia and Oceania Thyroid Society, the American Thyroid Association, the European Thyroid Association, the American Association of Clinical Endocrinologists and the Endocrine Society. In women not known to have thyroid dysfunction, universal screening during pregnancy is not recommended, but thyroid function tests are advised in those with prior therapeutic head or neck irradiation, a history of preterm delivery, in cases of infertility and in the presence of risk factors for thyroid disease. Risks factors for thyroid dysfunction are considered as a personal or family history of thyroid diseases, presence of thyroid antibodies (when known), personal history of autoimmune diseases and the presence of signs or symptoms suggesting hypo- or hyperthyroidism. In this review, we summarize the modifications of the pituitary-thyroid axis during pregnancy, with particular attention on thyroid insufficiency. We consider the most important risk factors for thyroid dysfunction and focus our attention on the complications for the progeny, deriving from a condition of maternal thyroid impairment. We will discuss the matters in favor of or against a thyroid-screening program at the beginning of pregnancy.