Most pregnant women in the U.S. use at least one prescription or over-the-counter medication—even though the safety of those drugs during pregnancy is not always clear, a new study finds.
Looking at data from two long-running studies, researchers found that by 2008, more than 80 percent of pregnant women used at least one prescription or over-the-counter medication at some point.
What's more, half used a drug during the first trimester—the point of pregnancy where there is the greatest concern about the potential effects of medications on birth defect risk.
Those numbers, the study found, represent a large shift from 30 years earlier, when about 30 percent of women used some type of medication during the first trimester.
The concern, researchers say, is that with many drugs, the safety of using them during pregnancy is not yet clear.
So the findings underscore a need to keep studying the safety of individual medications, according to lead researcher Dr. Allen A. Mitchell, of the Boston University Schools of Public Health and Medicine.
"That's not to say that these drugs are dangerous," Mitchell told Reuters Health. "But we just don't have enough information on them."
The difficulty is that medications are almost never tested in pregnant women before they come to market because it is considered unethical to expose a pregnant woman to a drug with unknown effects.
So usually the only way to uncover safety concerns is with post-marketing surveillance studies.
And those studies need to be large, Mitchell explained, in order to detect whether an individual medication is linked to any one birth defect. It's usually the case that a drug would cause only certain birth defects, as opposed to a broad spectrum of problems.
In general, the risk of having a baby with any birth defect is between 2 and 3 percent. So individual birth defects are relatively infrequent.
The current findings, which appear in the American Journal of Obstetrics & Gynecology, are based on data from two long-term studies on birth defects. More than 30,000 U.S. women were interviewed about their prenatal medication use.
Over time, the number of women using a prescription or over-the-counter drug rose, as did the percentage using four or more medications. By 2008, 28 percent of women said they'd used four or more drugs in the first trimester, up from 10 percent 30 years earlier.
Among the most common prescription drugs used were various antibiotics, asthma and allergy medications, and antidepressants.
The safety of those drugs during pregnancy is not entirely clear.
On the other hand, if a woman is taking a drug for a chronic medical condition, such as asthma, epilepsy or major depression, there could be risks to stopping the medication during pregnancy.
Mitchell pointed to the example of asthma. "Untreated asthma is not good for the mother or for the baby," he said.
These findings, he added, "should not discourage women from taking the medications they need for chronic conditions."
Instead, Mitchell suggested, these women should talk with their doctors about the risks and benefits of those drugs during pregnancy. Depending on the condition, there may be a particular drug that is recommended above others for pregnant women.
Women should also be aware that the safety of over-the-counter drugs during pregnancy is not completely clear either.
Again, Mitchell said, that's not to say that those medications are necessarily dangerous. But if a pregnant woman can find other ways to manage a stuffy nose or other minor symptom, then she might want to go that route.
"If you don't feel that you need the medication," Mitchell said, "then you might want to err on the side of caution."