The U.S. Food and Drug Administration (FDA) has created a labeling system that includes the pregnancy effects of drugs. The labels can help your health care professionals to make correct treatment decisions. The FDA requires drug labels to include whether the drug causes birth defects. Labels also must list any other effects on reproduction and pregnancy.

Drugs are put in one of five letter categories — A, B, C, D and X (see below). These groups are a general guide and can be somewhat confusing. The FDA is working on a new system.

Over-the-counter (OTC) drugs can be used during pregnancy under a doctor's care. However, some are known to be unsafe. Ask a doctor before taking OTC drugs if you:

• Are pregnant
• Are nursing
• May be pregnant

Aspirin should be avoided, especially during the last three months of pregnancy. The FDA issued a warning about this in 1990. It said not to use aspirin during the last trimester unless a physician tells you to do so. That's because aspirin can cause problems in the fetus (unborn baby) or make delivery more difficult. This warning also applies to nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. They also should be avoided during the third trimester.

The FDA groups drugs according to their risk of harming the fetus and other effects on reproduction or pregnancy. Here are the five categories:

Category A — Studies in pregnant women have not shown an increased risk of birth defects.

Category B — Animal studies have revealed no evidence of harm to the fetus. However, there are no adequate studies in pregnant women.
OR
Animal studies have shown an adverse effect, but adequate studies in pregnant women have failed to show a risk to the fetus.

Category C — Animal studies have shown an adverse effect and there are no adequate studies in pregnant women.
OR
No animal studies have been conducted or there are no adequate studies in pregnant women.

Category D — Adequate studies in pregnant women have demonstrated a risk to the fetus. However, the benefits of the drug may outweigh the potential risk.

Category X — Adequate studies in animals or pregnant women have shown evidence of birth defects. Women who are or may become pregnant should not use the drug.

For More Information
Organization of Teratogenic Information Services
http://otispregnancy.org/otis_fact_sheets.asp