Is it safe to take letairis (ambrisentan) while pregnant or breastfeeding?

No. Letairis or ambrisentan has been assigned to pregnancy category x by the fda. It is expected to cause fetal harm if administered to pregnant women.
NO. Letairis (ambrisentan) data shows it may cause serious birth defects. Women who are on Letairis (ambrisentan) are recommended to use at least 2 forms of contraception to prevent pregnancy. It is important to not get pregnant even after stopping the medication util it has had time to be excreted from your body.