Overview of hypothyroidism in pregnancy

Untreated or inadequately treated maternal hypothyroidism during pregnancy is associated with an increased risk of pregnancy complications (eg premature birth, low birth weight, miscarriage), as well as impaired fetal neurocognitive development. The risk of neurocognitive impairment may be correlated with the degree of thyroid stimulating hormone (TSH) elevation.

Routine testing of thyroid function in women who are pregnant or planning to become pregnant is only recommended in women at increased risk of a thyroid disorder. For information about risk factors, as well as thyroid hormone changes and reference ranges during pregnancy, see Thyroid function testing before conception and during pregnancy.

The goal of treatment of hypothyroidism in pregnancy is to achieve and maintain maternal serum TSH concentration within the trimester-specific reference range, using thyroxine replacement therapy. The principles of thyroxine replacement therapy for pregnant women are the same as for nonpregnant adults, although more frequent testing and dose adjustment may be required to maintain euthyroidism. Combination thyroxine (T₄) and triiodothyronine (T₃) therapy should not be used during pregnancy.

With adequate treatment of maternal hypothyroidism, maternal and fetal outcomes are similar to those of the healthy population.