In the United States, the FDA categorizes all medications for use in pregnancy. The categories are:
- Controlled studies in women taking these drugs have not demonstrated a risk to the developing baby in the first trimester, and there is no evidence of risk in later trimesters. The risk of harm to a developing baby appears remote.
- Animal studies have shown no risks for these drugs, and the drugs have not been tested in pregnant women, or animal studies on these drugs may have shown a risk to the animal fetus, but controlled studies in women have not shown the same effect on human babies. These drugs are probably safe, but if there have been animal studies showing risk, those raise concerns.
- Animal studies have shown a risk of fetal harm from these drugs, but there are no controlled studies in women; or there are no studies in animals or women on reproductive effects of these drugs. Unfortunately, most drugs fall into category C. The safety of using them during pregnancy is unknown.
- There is evidence that these drugs may harm developing human babies, but the benefit of the drug may outweigh the risk of the harm. If you are taking a category D drug to preserve your own health or life, you will need to talk with your health care provider to weigh the risks and benefits.
- These drugs have been shown to cause problems for the developing baby, and the risks that come with using the drugs during pregnancy clearly outweigh any benefit. These drugs should not be used during pregnancy.