Which antithyroid drug is recommended during the first trimester of pregnancy for Graves' disease?

Which antithyroid drug is recommended during the first trimester of pregnancy for Graves' disease?

• A. Methimazole
• B. Propylthiouracil (PTU)
• C. Carbimazole
• D. Levothyroxine

Answer: (B)

Choosing an antithyroid drug in early pregnancy hinges on minimizing fetal harm during organ development. Propylthiouracil is preferred in the first trimester because it has the lowest risk of causing congenital malformations compared with methimazole or carbimazole, which have been linked to teratogenic defects when exposure occurs during organogenesis. Although propylthiouracil carries a risk of hepatotoxicity, many clinicians switch to methimazole or carbimazole after the first trimester to reduce that risk while maintaining maternal control of hyperthyroidism. Levothyroxine is not used for Graves’ disease in pregnancy, as it treats hypothyroidism and would not address the hyperthyroid state.

Choosing an antithyroid drug in early pregnancy hinges on minimizing fetal harm during organ development. Propylthiouracil is preferred in the first trimester because it has the lowest risk of causing congenital malformations compared with methimazole or carbimazole, which have been linked to teratogenic defects when exposure occurs during organogenesis. Although propylthiouracil carries a risk of hepatotoxicity, many clinicians switch to methimazole or carbimazole after the first trimester to reduce that risk while maintaining maternal control of hyperthyroidism. Levothyroxine is not used for Graves’ disease in pregnancy, as it treats hypothyroidism and would not address the hyperthyroid state.