Thyroid Disease and Pregnancy
When pregnancy is associated with alterations in maternal thyroid function, the fetus can be affected in two ways: either directly by transplacental passage of maternal thyroid hormone, antithyroid antibodies, or medications, or indirectly by adverse influences on maternal physiology. It is important to recognize the expected alterations in thyroid hormone levels during gestation. The clinician must be able to differentiate normal physiologic changes from true thyroid disease. Hyperthyroidism and hypothyroidism may first be detected during pregnancy and patients with preexisting thyroid dysfunction require close monitoring, and frequently need adjustment of therapy.