Which anti-thyroid medication is avoided in the first trimester of pregnancy?

Which anti-thyroid medication is avoided in the first trimester of pregnancy?

• A. Methimazole
• B. Propylthiouracil
• C. Thyroidectomy
• D. Radioactive iodine

Answer: (A)

Exposure to methimazole in the first trimester is avoided because it has been linked to birth defects, including scalp defects (aplasia cutis) and other congenital malformations. To minimize fetal risk, propylthiouracil is typically used early in pregnancy, even though it carries a risk of maternal liver toxicity and may be switched to methimazole after the first trimester. Radioactive iodine is not used during pregnancy because it crosses the placenta and can harm fetal thyroid development, and thyroidectomy is a surgical option if antithyroid drugs are not suitable.

Exposure to methimazole in the first trimester is avoided because it has been linked to birth defects, including scalp defects (aplasia cutis) and other congenital malformations. To minimize fetal risk, propylthiouracil is typically used early in pregnancy, even though it carries a risk of maternal liver toxicity and may be switched to methimazole after the first trimester. Radioactive iodine is not used during pregnancy because it crosses the placenta and can harm fetal thyroid development, and thyroidectomy is a surgical option if antithyroid drugs are not suitable.