Today, there are a lot of drugs being found to cause adverse reactions and birth defects in pregnant women that weren’t found before. Many of these drugs have been on the market for years and were only found to cause issues when the women taking them gave birth. One class of drugs that may be included in this list of harmful medications is antihistamines. However, antihistamines may only be harmful to pregnant women. Other people taking them have not developed any illnesses or disorders.

Previous research has suggested that taking antihistamines while pregnant increases the risk of various birth defects as well as having low birth weight babies and premature babies. Women have taken antihistamines during pregnancy for many years. Usually, these drugs are taken to stave off nausea and vomiting caused by morning sickness. The drugs can be prescribed by a doctor or can be bought over the counter (OTC).

Recently, a new study was conducted to see if antihistamines increased the risk of specific birth defects. Research in the past showed that birth defects were more likely, but they never illuminated which types of defects were the most predominant.

Boston University's Slone Epidemiology Center interviewed over 20,000 new mothers to collect the needed research for the new study. The study was also used to see if other disorders were caused by taking antihistamines during pregnancy as well. The data collected by the interviews revealed that no further disorders are caused by taking antihistamines during pregnancy, and the types of birth defects caused by taking the drugs have not been pinpointed. From the data, it seems that no specific birth defect is more likely to occur than other defects.

In another study, however, it was revealed that birth defects as well as having low birth weight and premature babies were caused by taking specific OTC antihistamines, namely the drugs Unisom and Benadryl. These types of OTC antihistamines are commonly taken by women with a severe form of morning sickness called hyperemesis gravidarum (HG).

The studies together did not answer the primary question of the researchers, but it did reveal that more women are likely to suffer adverse consequences of taking antihistamines during pregnancy if they specifically take the OTC drugs Unisom and Benadryl. Other antihistamines, whether OTC or prescribed, were found to either cause a less severe outcome, or no adverse outcome at all.


  • Boston University Medical Center (2013, September 16). Risk of birth defects among women who take antihistamines in pregnancy. ScienceDaily.
  • University of California, Los Angeles (UCLA), Health Sciences (2013, June 10). Pregnant women with severe morning sickness who take antihistamines are significantly more likely to experience adverse outcomes. ScienceDaily.