Which medications fall under Category C and D for pregnancy?

Category C medications are those that have shown adverse effects on the fetus in animal studies, but there are no adequate and well-controlled studies in pregnant women. Some of these medications may be used if the potential benefits justify the potential risks to the fetus. Category D medications have evidence of human fetal risk based on adverse reaction data, but there may be situations where the benefits of the medication could outweigh the risks.

Warfarin, which is an anticoagulant, is well-known to pose serious risks during pregnancy, including teratogenic effects, making it a Category D drug. Lithium, often used for bipolar disorder, falls under Category D as well due to its potential risk of causing cardiac defects in the fetus. Phenytoin, an anticonvulsant, is classified as Category D because of risks such as fetal hydantoin syndrome, which involves a range of complications affecting the development of the fetus.

These examples fit firmly into the definitions of Categories C and D due to their known and researched risks associated with pregnancy, thus making this choice the correct one.