Background
Pregnancy is a unique time when the thyroid gland is under extra strain. Thyroid hormones help regulate metabolism, energy use, and fetal development, especially early in pregnancy when the baby depends on the mother’s hormone supply. Because of these demands, thyroid function tests are sometimes checked during pregnancy, either routinely or when there are risk factors such as a personal or family history of thyroid disease, autoimmune disease, infertility, miscarriage, or symptoms suggestive of thyroid dysfunction.
Two common findings can appear during pregnancy. One is subclinical hypothyroidism, which means the thyroid-stimulating hormone, or TSH, is elevated but free thyroxine remains within the normal range. The other is thyroid peroxidase antibodies, often called TPO antibodies, which suggest autoimmune thyroid activity even when hormone levels are still normal. Some individuals may have both.
