Propylthiouracil

Propylthiouracil-

Used for - Rx of hyperthyroidism
Pregnancy category - D
Crosses placenta - Yes
S/E - Can cause fetal goitre & cretinism in developing fetus
       - Can cause liver damage in mother & fetus

Alternative drug - Methimazole
       
Since methimazole may be associated with the rare development of fetal abnormalities such as aplasia cutis and choanal atresia, propylthiouracil may be the preferred agent during organogenesis, in the first trimester of pregnancy.
Given the potential maternal adverse effects of propylthiouracil (e.g., hepatotoxicity), it may be preferable to switch from propylthiouracil to methimazole for the second and third trimesters.