The use of any type of drugs, whether prescription or recreational, can have profound effects on the health of a developing fetus or the natural course of a pregnancy. In some cases, drug use may cause birth defects or other damage. Maternal drug use is thought to be responsible for at least 10 percent of birth defects, according to the American Academy of Family Physicians (AAFP). For this reason, women who are pregnant or thinking about becoming pregnant should consult with a physician before taking any medications.

The most cautious approach is not to use any medications during pregnancy. However, this is not a practical solution for most women. More than 80 percent of pregnant women take over-the-counter or prescription drugs during pregnancy, according to the AAFP. Pregnant women may need to take prescription drugs to treat conditions such as asthma, epilepsy, high cholesterol or depression. In addition, women may take over-the-counter medications to treat less severe conditions such as allergy flare-ups or minor pain. Furthermore, some drugs may be necessary during a pregnancy to treat pregnancy complications, such as gestational diabetes, preterm labor or preeclampsia.

No medicines have been proven absolutely safe for use during pregnancy, according to the U.S. Department of Health and Human Services. However, many over-the-counter and prescription drugs are thought to be safe for pregnant women. Nonetheless, others are not, including some medications that a woman may have taken safely before she became pregnant

Finally, many illegal drugs (such as marijuana and cocaine) and legal drugs, herbs and supplements (such as nicotine, alcohol, caffeine, vitamins, herbal teas and remedies) can have adverse effects when taken during pregnancy.

The risk of drug damage to a fetus is highest during the first several weeks of pregnancy, when major organs are developing. However, experts are unsure whether medications during pregnancy cause negative effects that manifest in the child later in life. In addition, the use of some drugs can negatively impact the pregnancy, such as increasing the risk of premature labor or certain types of complications, such as separation of the placenta or other bleeding problems.

For these reasons, female patients should tell all healthcare providers if they are pregnant or thinking about becoming pregnant. This can help alert physicians to avoid prescribing certain drugs, or to suggest alternatives that may be safer to use during pregnancy. Women with certain medical conditions (e.g., heart disease) might need to change their medications prior to attempting to conceive. In addition, they may need to modify or add dietary supplements. Women can also carefully check the labels of over-the-counter drugs before they purchase them. Federal law requires that all drugs known to increase risks for pregnant women must state this clearly on the packaging.

Women should remember that in many cases, the benefit of taking certain drugs far outweighs any potential risks for the mother and the fetus. In other cases, some drugs or supplements – such as folic acid (which helps prevent fetal brain and spinal cord disorders), calcium and iron – may be beneficial just before and during pregnancy.