In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This sheet talks about whether exposure to diphenhydramine may increase the risk for birth defects over that background risk. This information should not take the place of medical care and advice from your health care provider.

What is diphenhydramine?

Diphenhydramine is an antihistamine. It is found in many medications, both prescription and over-the-counter. It is commonly used to treat allergy symptoms, and may also be used to treat nausea, motion sickness, insomnia, itchy skin, and tremor of Parkinson’s disease. Some of the brand names for diphenhydramine include: Benadryl®, Unisom®, Sominex®, or Nytol®.

I just found out I am pregnant. Should I stop taking diphenhydramine?

You should always talk with your health care provider before making any changes in your medication. It is important to consider the benefits of treating allergy symptoms and other conditions during pregnancy. Treating allergy symptoms may reduce asthma symptoms and the need for more asthma medicine. Allergy treatment can also result in better sleep and emotional well-being.

Can use of diphenhydramine during pregnancy cause birth defects?

It is unlikely that diphenhydramine would cause an increased chance for birth defects. Most studies show no increased chance of birth defects with the use of diphenhydramine in early pregnancy. While one study suggested an increased chance of several types of birth defects, the study does not prove causation and these findings have not been confirmed.

Can use of diphenhydramine cause other pregnancy complications?

At recommended doses, diphenhydramine has not been shown to cause problems in pregnancy. There are rare reports of problems with the use of diphenhydramine in the third trimester. These reports usually involve using more of the medication than is recommended or using it for long-term (chronic) use. High levels of diphenhydramine could cause uterine hyperstimulation (contractions that are too long or too often). Uterine hyperstimulation can affect the developing baby such as increasing the baby’s heart rate. Uterine contractions can also lead to serious complications, including uterine rupture (a tear in the uterus) or placental abruption (when the placenta pulls away from the wall of the uterus before the baby is born).

Also, there are a few reports of withdrawal symptoms in infants whose mothers took diphenhydramine daily throughout pregnancy.

Is there anyone who should avoid taking diphenhydramine during pregnancy?

A single human report and animal data have suggested that the combination of two medications: temazepam (a benzodiazepine) and diphenhydramine may increase the chance for stillbirth or infant death shortly after birth. It is unknown if this interaction will occur with all medications in the benzodiazepine class. Women taking benzodiazepines should talk with their health care provider before taking diphenhydramine during their pregnancy. For more information, see the MotherToBaby fact sheet on benzodiazepines at: https://mothertobaby.org/fact-sheets/benzodiazepines-pregnancy/pdf/.

Can I breastfeed while taking diphenhydramine?

Because diphenhydramine can cause sleepiness in adults, it may do the same for the baby. If you need to take an antihistamine regularly, ask your health care provider if a non-sedating one would work for your symptoms.

Antihistamines, as a group, might lower the amount of milk a woman makes, especially when using long acting antihistamines and when used with decongestants like pseudoephedrine or phenylephrine. This is less likely to be of concern in a woman with established milk supply (has been breastfeeding for a while).

Two studies with women who used an antihistamine (not just diphenhydramine) while breastfeeding reported their babies were irritable, sleepier, and/or slept less.

Be sure to discuss any medications you are taking and your options for breastfeeding with your health care provider as well as the baby’s pediatrician.

What if the father of the baby takes diphenhydramine?

There are no studies looking to see if a man’s diphenhydramine use would cause any problems for conceiving or problems during a partner’s pregnancy. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures and Pregnancy at: https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/pdf/.

References Available Upon Request.