Safety of Antihistamines During Pregnancy

Antihistamines are commonly used medications for the treatment of allergic rhinitis, as well as other medical problems such as insomnia, nausea and vomiting, motion sickness and dizziness. These medications are also commonly used during pregnancy, as many are available over-the-counter (OTC) without a prescription.

However, while generally considered “safe” during pregnancy, there are a number of past associations between pregnant women taking antihistamines during the first trimester and various birth defects.

A pregnant business woman blowing her nose
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Possible Associations Between Antihistamines and Birth Defects

Associations between antihistamines taken during the first trimester of pregnancy and certain birth defects include:

  • Diphenhydramine (Benadryl): Cleft lip and cleft palate, neural tube defects, spina bifida, limb reduction defects, gastroschisis.
  • Loratadine (Claritin): Hypospadias.
  • Chlorpheniramine (Chlor-Trimeton): Eye defects, ear defects, spina bifida, cleft lip, and cleft palate.
  • Doxylamine (Unisom): Cleft lip and cleft palate, pyloric stenosis, hypoplastic left heart syndrome, spina bifida, and neural tube defects.

Nearly 15% of pregnant women report taking an antihistamine during their first trimester.

Study of Antihistamines in Pregnancy

A group of researchers from Boston Massachusetts and Singapore sought to determine the safety of antihistamines taken during the first trimester of pregnancy.

The data from this study is extremely encouraging that antihistamines are generally considered safe during pregnancy. The previous associations between antihistamine use during the first trimester and birth defects was not confirmed in this study.

The researchers examined data collected over a 12-year period of time, from 1998 to 2010, on over 13,000 babies born with birth defects, and compared them to nearly 7,000 babies without birth defects. Approximately 14% of all babies had been exposed to various antihistamines the mother took during the first trimester of pregnancy. Some antihistamines, such as Benadryl and Claritin, have increased in pregnancy use over the years, while the use of other antihistamines, such as Chlor-Trimeton and Unisom has decreased.

However, in an attempt to assess the risk of developing other common birth defects, the researchers did find an association between the use of Chlor-Trimeton and any neural tube defect and with various congenital heart malformations. There was also an association between the use of Benadryl and one type of congenital heart malformation (transposition of the great arteries). However, the authors are careful to point out that these are only hypotheses that require further study.

Therefore, while there is no such thing as a completely safe medication during pregnancy, the past association between antihistamine use during the first trimester and birth defects was not confirmed in a recent large study.

Even though most antihistamines are available OTC without a prescription, pregnant women should seek the advice of a physician prior to taking any medication, particularly during the first trimester of pregnancy.

Any medication taken during pregnancy is best taken for the shortest amount of time, and at the lowest dose that is effective for treating symptoms. The benefit of taking any medication needs to be weighed against the risk of not taking the medication.

2 Sources
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  1. Honein MA, Moore CA. The safety or risk of antihistamine use in pregnancy: reassuring data are helpful but not sufficientJ Allergy Clin Immunol Pract. 2013;1(6):675–676. doi:10.1016/j.jaip.2013.08.005

  2. Li Q, Mitchell AA, Werler MM, Yau WP, Hernández-Díaz S. Assessment of antihistamine use in early pregnancy and birth defectsJ Allergy Clin Immunol Pract. 2013;1(6):666–74.e1. doi:10.1016/j.jaip.2013.07.008