How Safe Are Prescription Medications During Pregnancy?
In most cases, doctors do not have clear, definitive answers about the safety of prescription medications during pregnancy. Instead, they must make judgment calls about the potential risks and benefits of each medication based on available data and the particular needs of each patient. Women who may become pregnant should always consult their health care providers about any prescription medications they may be taking.
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Considerations
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Because of the ethical considerations involved in testing prescription medications on pregnant women, most drug companies rely primarily on animal studies. Although testing prescription medications at high doses in rats and rabbits can provide some clues to their potential effects on the reproductive system, not all drugs that are harmful to humans cause problems in animals, and vice versa. Many human studies use only small groups of participants, and may not always use a control, or placebo, group to ensure reliable data.
Identification
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The FDA classifies prescription medications as "A," "B," "C," "D" or "X" for use during pregnancy. In many cases, these ratings reflect how many reliable studies have been done with the medications, rather than a scale of how harmful they may be. Only class "A" drugs have had sufficient human studies to be proven safe. Conversely, human studies have proven that class "X" drugs cause birth defects or significant complications, and that class "D" prescriptions may have serious risks. With many class "B" drugs, animal studies have shown no evidence of harm, but there have not been enough human studies to prove they are safe. In other cases, class "B" drugs have caused problems in animal studies, but not in human studies. Many class "C" drugs have shown problems in animals, but lack adequate human studies.
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Time Frame
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Some prescription medications that are especially harmful to a developing baby, such as accutane, thalidomide and soriatane can cause birth defects even if a woman stops taking them before she becomes pregnant or as soon as she receives a positive pregnancy test. Although many prescription medications are most harmful during the first trimester of pregnancy, others are only unsafe later on, as the organs develop more fully. For this reason, some prescription drugs have different classifications during different stages of pregnancy.
Benefits
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In each case, doctors and patients must decide whether a medication's benefits outweigh the potential risks, especially for class "B," "C" and "D" prescriptions. Doctors will avoid prescribing medications that have not been proven to be safe if a less risky alternative is available. However, in some cases, a pregnant woman may require medication to treat a serious health condition, even if that medication is known to have some risks. For example, many health care professionals recommend that most pregnant women avoid using aspirin during pregnancy because of possible bleeding complications. For women with serious blood clotting disorders, however, the risks associated with leaving the disorder untreated may be far worse than the risks of taking aspirin and heparin throughout pregnancy.
Effects
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While some prescription drugs, such as thalidomide, can cause obvious heart and limb defects that are often apparent on an ultrasound before a baby is born, others may cause subtle, long-term effects such as behavior problems that are more difficult to prove. For example, researchers are still debating whether medications such as anti-depressants have significant long-term effects on the baby. Women who may be pregnant should always consult their health care providers before starting, stopping or changing the dosage of a prescription medication, since all of these actions can have significant health consequences.
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