It’s clear that for pregnant women and the physicians who care for them, the risk of using medications in pregnancy is a significant issue. Unfortunately, sometimes the perception of that risk is much greater than the reality and drives behavior that can harm women and their babies.

Before the tragedy of thalidomide, the medical community held the general belief that drugs and chemicals do not cross the placenta, so there was no need to fear fetal malformations from medication use in pregnancy. In 1961, thalidomide became a formative event that changed everyone’s perception, with many people adopting the belief that every drug could be dangerous. In reality, though, very few medications prescribed today are known teratogens that cause malformations.

In recent years, an increasing number of drugs have been shown to be “safe.” The issue with the term safe is that there can always be more cases and more studies showing some very small risk that was previously unknown. But, in general, there are more reassuring studies in the literature than ones showing drugs to be dangerous in pregnancy.

The Bendectin example

In the highly charged medicolegal atmosphere in which we practice, physicians are afraid to be sued. If you remember that about 3% of babies are born with malformations just by chance, and that mothers will likely be taking some type of medication, there is always the possibility of a bad outcome that could cast blame on a drug.

In the 1970s, a lot of that litigation centered around the morning sickness drug Bendectin – originally formulated with doxylamine succinate, pyridoxine HCl, and dicyclomine HCl, and later reformulated without the dicyclomine. The drug was taken off the U.S. market by the manufacturer in 1983 because the company couldn’t afford the high cost of litigation and insurance, despite the fact that a panel convened by the Food and Drug Administration said there was no association between Bendectin and human birth defects.

It took nearly 20 years before the FDA declared that the drug had been withdrawn from the market for reasons unrelated to safety and effectiveness. In the meantime, American women remained without an FDA-approved medication to treat morning sickness, and there was a more than twofold increase in hospitalization rates for pregnant women with hyperemesis gravidarum ( Can J Public Health. 1995 Jan-Feb;86[1]:66-70 ). The lesson here is that perceptions in the absence of evidence can lead to grave outcomes.

Exaggeration of risk

Over the years, my colleagues and I have studied how pregnant women perceive drug risk by simply asking them to estimate the risk to their baby from the medication they are currently taking. What we discovered was that women exposed to nonteratogenic drugs consider themselves at a risk of about 25% for having a child with a major malformation. In reality, the risk is between 1% and 3% and has nothing to do with the drug itself. It became clear that there is a huge perception of risk when women are exposed to drugs that should not increase that risk ( Am J Obstet Gynecol. 1989 May;160[5 Pt 1]:1190-4 ).

The same study also showed that many of the women who gave exaggerated risk assessments said they would consider termination of the pregnancy. Even after hearing the drug is safe, some women were still considering termination.

Sadly, women terminating a pregnancy because of a perceived risk for malformation is not unique to this study. In the 1980s, following the explosion at Chernobyl in the Ukraine, women in Athens were told that they had a high risk for malformation in their children because of radiation exposure. Statistics show that during that month, nearly a quarter of early pregnancies in Athens were terminated ( Br Med J [Clin Res Ed] 1987;295:1100 ).

We have further found that women exposed to radiation for diagnostic purposes estimate a high risk of malformation. This type of estimate is likely influenced by the effects of radiation at Hiroshima and Nagasaki, but there is no comparison between the extremely high amounts of radiation in those incidents, compared with the very low amounts in diagnostic tests. Still, we found that women again considered termination because of their perceived risk from radiation.

Social economics are also part of this. Women who are single mothers are more likely to terminate a pregnancy, or consider termination, after exposure to a drug in pregnancy. Women with psychiatric conditions have a similar tendency. On the other hand, women with chronic diseases – who may be used to the effects of a certain medications – are less likely to suggest termination because of perceived risk.

Communicating risk

These are important concepts to consider in the context of the emerging threat of Zika virus and the news from the Centers for Disease Control and Prevention that it is a definitive cause of microcephaly and other severe fetal malformations. While there is a real risk for pregnant women, both through mosquitoes and sexual contact, women are likely to perceive the highest level of risk. In South America, where therapeutic abortion is often not an option, accurate risk communication is critical.

When medications are prescribed during pregnancy, the first step is determining that a drug is truly needed, often in consultation with a specialist. Once that determination is made, it’s key to ensure that women and their families are familiar with the known risk or the lack of risk based on the best available data. There are resources for physicians to help understand and communicate about drug risks in pregnancy, including information from the Organization of Teratology Information Specialists. It’s also important to note that in every pregnancy, there is a 1%-3% risk of major malformations, even if the drug itself is safe. And it can’t hurt to think defensively and document that conversation and that the patient appears to have understood the concept of risk.

Dr. Koren is professor of pharmacology and pharmacy at the University of Toronto. He is the founding director of the Motherisk Program. He reported having been a paid consultant for Novartis and for Duchesnay, which makes Diclegis to treat nausea and vomiting in pregnancy.