Methimazole and Pregnancy
It is very important for pregnant women to receive adequate hyperthyroidism treatment during pregnancy, as leaving the condition untreated puts the fetus at risk of birth defects and other problems. Methimazole (Tapazole) is generally not recommended for women who are expecting, except in cases where the benefits outweigh the risks. A different antithyroid medication is preferred for pregnant women, especially during the first trimester.
Methimazole (Tapazole®) is a prescription medication used to treat hyperthyroidism (an overactive thyroid). This antithyroid medication may pose some risk to the developing fetus if taken during pregnancy.
What Is Pregnancy Category D?
The U.S. Food and Drug Administration (FDA) uses a category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category D is given to medicines that have been shown to present a risk to the fetus in studies of pregnant women but may still offer benefits that outweigh this risk.
Methimazole crosses the placenta and has been possibly linked to a number of birth defects, although the risk of such birth defects appears to be low. It is also important to understand that untreated hyperthyroidism is also associated with problems, such as certain birth defects, so it is essential that pregnant women be adequately treated for this condition.
Some experts believe that a different antithyroid medication (propylthiouracil or PTU) is preferred for pregnant women, especially during the first trimester.
No matter what treatment is chosen, your healthcare provider should monitor your thyroid closely during pregnancy, as this affects thyroid function.