Is it safe to take toprol-xl while pregnant or breastfeeding?

OK. As such nothing is safe to take during pregnancy except vitamins. Most of the medications are ok after 1st trimester of pregnancy. Toprol (metoprolol) being a beta-blocker can also slow baby's heart beats and therefore you have to have a real solid reason to take this medication and needs close fu with your OB &gyn.
Yes. It's a pregnancy category c drug, so ok to use when benefits outweigh risks. Talk to your provider.