Health risks of taking drugs during pregnancy

Surprising answers to commonly asked questions

Published: July 2014

Photo: Getty Images

A pregnant woman today is far more likely to take medications during pregnancy than her mother did. Use of medications during the first trimester of pregnancy has increased by more than 60 percent over the last three decades in the U.S. Today, on average, pregnant women take three to five different medications; few moms-to-be make it through the entire 9 months without taking at least one drug.

Of course, drugs can be an essential part of medical treatment. But pregnant women may not be as cautious as they should be about medications. They might take for granted that if a drug was prescribed by their doctor, or is available over-the-counter, then it must be safe. But the truth is, there’s often very little evidence to back up that assumption.

Some drugs are known to pose a danger to pregnant women or their unborn babies. Examples include the acne drug isotretinoin (Absorica, Sotret), the blood thinner warfarin (Coumadin and generic), cholesterol-lowering statin drugs, and the ulcer drug misoprostol (Cytotec and generic) and also a component of the arthritis drug Arthrotec. But, for most drugs, the pregancy risks are not well known. Only two of the 54 prescription and over-the-counter medications used most commonly by women during the first trimester of pregnancy have been studied enough to solidly assess whether they cause birth defects, according to a 2013 study by the Centers for Disease Control and Prevention.

“The absence of data on safety does not mean that a drug is safe,” says Allen Mitchell, M.D., professor of epidemiology and pediatrics at the Boston University School of Public Health and Medicine and director of the Slone Epidemiology Center, one of the leading research facilities studying the use of medications during pregnancy and birth defects. He worries that this basic fact is not well understood—even by health professionals. Internet lists of “safe” drugs for expectant mothers frequently contain medications that have simply not been studied for use during pregnancy.

To make matters worse, the Food and Drug Administration is dragging its feet requiring drug labels to clearly state what is known about the risks.  

All of which leaves a mom-to-be with a headache, upset stomach, or more serious condition such as diabetes or depression in a terrible quandary. How can she safely address her own health needs while still protecting her unborn child?

To answer your questions, CR Best Buy Drugs commissioned an analysis by the American Society of Health-System Pharmacists on the safety of medications during pregnancy. We also talked to the experts and reviewed the latest evidence. The resulting advice is pertinent to all women who could become pregnant, as an estimated half of pregnancies are unplanned and many medication exposures happen during the first weeks before a woman is even aware she has conceived. For that reason, women of childbearing age should have a frank discussion with their health-care providers about factors that could affect a pregnancy, including smoking, alcohol use, and everything they take—prescription and OTC drugs, vitamins, minerals, and herbals.

How does something I take affect my baby?

Photo: RusN

Drugs taken in the first week after an egg is fertilized tend to have an “all-or-nothing” effect—they can cause no harm, but when they do, it usually results in loss of the embryo.

Once the fertilized egg implants in the womb, a major concern is that a medication will cross the placenta into the baby’s bloodstream and disrupt development. The type and severity of harm that a drug can cause often depends on the stage of pregnancy. The most severe birth defects usually occur during the first trimester—particularly weeks 2 through 8—when the major organs and body parts develop.

For example, babies are at greater risk of having a neural tube birth defect if their mothers take opioids, prescription painkillers such as oxycodone (OxyContin and generic) and hydrocodone combined with acetaminophen (Lortab, Vicodin and generic) during the first two months of pregnancy according to results from a 12-year analysis conducted by researchers at Boston University and the CDC published in 2013.

In the second and third trimesters, certain drugs can affect the baby’s growing brain, potentially resulting in intellectual and social problems in childhood. For example, one recent Danish study of more than 64,000 children found that those whose mothers took the OTC pain reliever acetaminophen (Tylenol and generic) during pregnancy may be at higher risk for attention deficit disorder and behavior problems. Risks were negligible for women who used the drug occasionally (less than seven days total) or only during the first trimester only, but increased the longer women used the drug and were much higher for women using the drug during both the second and third trimesters.

It’s important to keep medication risks in perspective. All women face a 3 to 4 percent chance of having a baby with a birth defect. Oftentimes the added risk of a birth defect associated with use of a medication is still very low. The study cited above, for example, found double the risk of neural tube defects in infants whose mothers took opioids, but the absolute risk remained small: for every 10,000 pregnant women taking the prescription painkillers, an estimated 6 babies would be affected.

For more information, read our report on 10 OTC drugs to avoid during pregnancy.

Are drugs tested for safety in pregnant women?

No. Before the FDA approves a new drug, the manufacturer has to submit data showing that it is safe and works as intended. But women who are pregnant or may become pregnant are almost always excluded from clinical drug trials because of concerns about safety and liability. Instead, drugs are tested to see whether they cause birth defects in pregnant animals, but those results are not entirely accurate at predicting any effects on the human fetus.

However, in 2007 Congress gave the FDA the authority to require drug makers to study the effects of newly approved medications in pregnant and nursing women who take them. The main way drug companies and research institutions do this is through pregnancy registries, studies that collect and maintain data on approved treatments for a range of illnesses such as HIV/AIDs, cancer, diabetes, and asthma. Pregnant or nursing women who take medications can sign up for a registry, and researchers can then compare the information they provide to the effects of the drug in women who are not pregnant. For example, Massachusetts General Hospital in Boston maintains a national registry for women who take anti-epileptic drugs.

“A huge part of what we do is observational research and to do that we depend on women to share their experience,” says Christina Chambers, Ph.D., M.P.H, professor of pediatrics and family and preventive medicine at the University of California San Diego School of Medicine and program director for MotherToBaby California. “Then we can put it all together and communicate what’s known so that women are not navigating in the dark about what they can and can’t do during pregnancy.” The nonprofit Organization of Teratology Information Specialists runs MothertoBaby chapters as a service to provide information to mothers and health care providers across the U.S. and Canada on the effect of medications and other environmental exposures on pregnancy and breastfeeding.

If you would like to add your experience to the growing body of data, your health-care provider or pharmacist can likely refer you to an appropriate registry. In addition, you can contact OTIS at and check out a list of registries compiled by the FDA.

Is it better to not take any medications at all?

Not necessarily. It does make sense to be cautious and try nondrug measures for many minor, short-term health problems. For example, instead of reaching for antihistamines and decongestants when you have a cold, try safer alternatives first: get extra rest; drink liquids; gargle with warm saltwater; and suck on nonmedicated lozenges. However, for more serious ailments, treating it with medication is often better for both you and your baby.

Asthma is a perfect example. “Pregnant women with asthma tend to undertreat themselves out of fear that they could harm their baby. But poorly controlled disease may be much more likely to adversely affect the pregnancy,” Chambers says. Uncontrolled asthma can lead to pregnancy complications such as high blood pressure, problems with the placenta, an increased risk of delivering the baby too early, and infants with low birth weights.

Women with other chronic health conditions such as diabetes, depression, epilepsy, and high blood pressure should work closely with their health care providers to find the safest way to manage their symptoms, keeping in mind that may mean taking a medication. (See the following question.)

You should also promptly report illnesses that crop up during your pregnancy to your provider and treat them as necessary. For example, research finding a possible link between frequent use of acetaminophen by pregnant women and behavior problems in children shouldn’t discourage you from using appropriate medication short-term to treat a high fever, says Chambers. A sustained elevated body temperature during pregnancy can slightly increase the risk of birth defects; a 2010 study found that using acetaminophen to lower fever might reduce or eliminate that risk.

Should I stop taking medication for my ongoing condition if I become pregnant?

Not necessarily. The decision about whether to continue a medication during pregnancy depends on several factors such as the condition being treated, the severity of your symptoms, the type of medication you take, and the degree of risk to the fetus. Ultimately, it’s a decision you should make together with your provider based on what’s best for you and your pregnancy. And the ideal time to discuss it is before you become pregnant.

In some cases, it may make sense to continue your current regimen unless something changes during pregnancy. While the diabetes drug metformin (and generic) appears to pose little risk to the fetus, for example, uncontrolled blood sugar can increase your risk of birth defects, miscarriage, and stillbirth.

Sometimes switching to a different drug may be the best choice. In general, older drugs with a history of safe use during pregnancy are preferred to newer drugs that may be slightly more effective, but whose safety is uncertain. For example, older high blood pressure drugs such as labetalol (Trandate and generic) and methyldopa are preferred over newer ACE inhibitors such as enalapril (Vasotec and generic) and lisinopril (Prinivil, Zestril, and generic).

If there are no good alternatives or the risks are not well known, you should consider other options. You may be able to reduce your dose or discontinue the drug for the period during pregnancy when it is most likely to cause a problem—say, the first trimester. Or ask your provider if you can wean off certain medications before becoming pregnant. For example, if you take a drug for mild depression you might be able to substitute nondrug measures such as cognitive behavior therapy and increased physical activity. However, you need to be monitored closely and if symptoms return, it may be better for both you and your baby to treat them with medication. By themselves, poorly managed anxiety, depression, and other mental disorders have been linked to increased risks, including premature birth and low-birth weight.

Is it safe to take drugs sold over-the-counter?

Not always. Some common OTC medications such as aspirin could harm you or your baby if you take them while pregnant. For further advice, read our latest report on 10 OTC drugs to avoid during pregnancy

You should also talk to your health-care provider before using any vitamins, minerals, or herbal preparations. While prenatal vitamins can help you meet the extra nutritional needs of pregnancy, other supplements may not be safe. For example, taking more than 3,000 micrograms (10,000 IU) daily of preformed vitamin A is linked to an increased risk of birth defects. As with prescription drugs, for many OTC products, including “natural” remedies, the risks are not well known.

Will the label say if a drug is safe to take when I’m pregnant?

Not usually. Drug labels rely on a system that is well over three decades old to express pregnancy risk (see the table below). Most drugs wind up in category C, which gives women and their providers little information to go on when weighing the risks and benefits of taking a drug. “Basically, category C says ‘you figure it out,’” says Chambers. “What kind of advice is that?”

In May 2008, the FDA proposed a useful, evidence-based alternative that included three essential areas of information:

  • A fetal risk summary, an outline of what’s known about the drug’s potential to cause birth defects.
  • Clinical considerations, with details about inadvertent exposure (before women realize they are pregnant, for example), advice about prescribing the drug, and potential effects during labor and delivery.
  • A data section, a detailed discussion of the available data from studies of humans and animals exposed to the drugs. 

But, years later, those changes still await finalization. While some drug makers are voluntarily using the new labeling on a few products, the agency has yet to require it. A spokesperson for the FDA said the agency hopes to issue a final ruling “soon,” but could not provide an estimate of when.

We think women deserve better drug labeling than confusing, possibly inaccurate information based on a system created in the 1970s.

Current Categories for Drug Use in Pregnancy




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


Animal studies have shown no evidence of harm to the fetus; however, there are no good-quality studies in pregnant women.




Animal studies have shown an adverse effect, but studies in pregnant women have failed to show a risk to the fetus. 


Animal studies have shown an adverse effect, and there are no good-quality studies in pregnant women.




No animal studies have been conducted, and there are no good-quality studies in pregnant women.

D Studies in pregnant women have found a risk to the fetus. However, the benefits of taking this drug may outweigh the potential risk.
X Studies in animals or pregnant women have found proof of birth defects. The drug should not be used in women who are or may become pregnant.

Does it matter what medications my male partner takes?

It can. A few medications present in the semen at conception such as the acne drug isotretinoin (Accutane) and the rheumathoid arthritis drug methotrexate (Trexall and generic), can potentially pose a risk to the fetus. For that reason, it’s a good idea to talk to your health-care provider about your male partner’s health history, including the medications he takes, before becoming pregnant. In addition, several common medications, including certain antidepressants, antifungal medications, and prescription painkillers can reduce fertility in men.

What if I took a drug before I knew I was pregnant?

That’s extremely common, so don’t panic. Contact your health-care provider right away and list everything you have taken recently, including all prescription and OTC medications and supplements. And, yes, you should also fess up to drinking alcohol, smoking or using recreational drugs. A good health care provider will focus on the health of you and your unborn baby, not judge your lifestyle choices.

In her role with MotherToBaby, Chambers and her colleagues frequently counsel women in this situation and remind them not to overreact. “People tend to think in absolutes, that the chance of a drug causing a problem is either 100 percent or zero,” says Chambers. “Fortunately, for most medications that have been carefully studied in pregnancy, there is no evidence of an increase over the general risk. But even for the few medications that have been found to pose a risk, often it’s still low.”

Where can I get reliable information about medication risks?

Chambers says to start with your health-care provider, but if you still have questions, it’s a good idea to consult other reliable resources as well: “It’s really hard for health-care providers to stay on top of the latest findings.”

Other resources include:

  • MotherToBaby, a service of the nonprofit Organization of Teratology Information Specialists (OTIS). Go to or call toll-free to talk to an expert counselor at 866-626-6847. Health care professionals are encouraged to use the service as well. In fact, Chambers reports that about one-third of callers are providers.
  • Treating for Two, a public health initiative run by the CDC in conjunction with the FDA and other non-government partners, is another good resource for both families and providers. Visit
Editor's Note:

This article and related materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multistate settlement of consumer-fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).

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