What is the best anti-thyroid regimen in a pregnant woman who has clinically significant hyperthyroidism?

Propylthiouracil (PTU) is recommended for treatment of hyperthyroidism in women who are in their first trimester of pregnancy by the American Thyroid Association (ATA). Methimazole has been associated with congenital malformations including aplasia cutis in rare cases and thus it is not recommended in the first trimester. The ATA recommends switching to methimazole once in the second trimester as there is a risk of liver injury associated with the use of PTU.