Is it safe to take nifedipine while pregnant or breastfeeding?

Yes: It is category c, not shown to be harmful in humans but some concerns in animals. It is and has been used in preg for some time now. The benefits freq outweigh risks.

Maybe: It is pregnancy safety class c - animal studies show adverse fetal effect but no contolled human studies have been done. It is "probably safe" for lactation with limited studies showing no adverse effect.