What pregnancy category indicates no risk to the fetus?

The correct answer is Category A, as this category indicates that there is no risk to the fetus based on well-controlled studies in pregnant women. This classification is part of the FDA's pregnancy category system, which is used to assess the safety of medications during pregnancy.

Drugs assigned to Category A have shown no evidence of harm to the fetus in any trimester of pregnancy and are considered safe to use during pregnancy. These drugs can be prescribed with confidence that they do not pose a risk to fetal development based on the available data.

In contrast, drugs in Category B may be considered safer than those in Category C, but they have not been conclusively tested in pregnant women. Category C includes drugs that have shown adverse effects on the fetus in animal studies but for which there are no adequate human studies. Category D drugs have demonstrated evidence of risk to the fetus; however, they may still be used in certain critical situations where the benefits may outweigh the risks. Thus, Category A stands out as the only category that indicates a complete absence of risk to the fetus.