Pregnant Women on Thyroxine Substitution Are Often Dysregulated in Early Pregnancy

Abstract

In 49% of pregnant women on thyroxine substitution, serum TSH values were outside the reference range when first tested, generally in the first trimester. Fetal loss was significantly greater in pregnant women with abnormal TSH values compared to those with normal TSH values. Thyroid function in pregnant women on thyroxine substitution should be monitored early in pregnancy and carefully followed during pregnancy. The thyroxine dose should be increased as needed early in pregnancy to avoid hypothyroidism.