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 chlorpheniramine 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 chlorpheniramine?
Chlorpheniramine is part of a group of medications called antihistamines.  Antihistamines are medicines used for allergic reactions and colds. Chlorpheniramine is used to relieve allergy symptoms, including sneezing, runny nose, watery eyes and itchy throat. Chlorpheniramine is sold under brand names that include Chlor-Trimeton®.  Chlorpheniramine has been in prescription and over-the-counter medications.

How long does chlorpheniramine stay in the body? Should I stop taking it before I try to get pregnant?
Individuals break down medicines at different rates. The average time it takes for one half of the medicine to leave the body is about 20 hours (a little less than one day). This means that about 5 days after taking the last dose of chlorpheniramine, most of the medicine will be gone from the body.

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 additional asthma medicines.

Can taking chlorpheniramine make it more difficult for me to become pregnant? Could it cause a miscarriage?
We have not located studies that try to see if chlorpeniramine has any effect on human fertility. At this time, it is not known if taking chlorpeniramine would make it more difficult for a woman to get pregnant or if it would increase the chance of a miscarriage.

Can taking chlorpheniramine during pregnancy cause birth defects?
It is unlikely that chlorpheniramine would cause an increased chance for birth defects. Most studies find no overall increased chance of birth defects with the use of chlorpheniramine in early pregnancy. While two studies found a small increased chance for different types of birth defects, no pattern has been detected. At this time, reports describing birth defects with first trimester chlorpheniramine cannot be considered proof of risk and it is likely that these problems were due to chance.

Can use of chlorpheniramine cause other pregnancy complications?
There are no data to suggest chlorpheniramine can cause pregnancy complications.

Can I breastfeed while taking chlorpheniramine?
Because chlorpheniramine can cause sleepiness in adults, it may do the same for a nursing baby.  For this reason it may not be a preferred antihistamine for long-term use during breastfeeding.  If you need to take an antihistamine regularly while breastfeeding, ask your health care provider if another medicine might work for your symptoms.

Small amounts and occasional use during breastfeeding would not be expected to cause problems for a baby. When five women were asked about their infant’s behavior after the mother used chlorpheniramine and breastfed, the mothers did not report any symptoms in their babies.

It is possible, but not proven, that antihistamines in general may lower the amount of milk a woman makes.  This might be more likely to happen when used in combination with an oral (taken by mouth) decongestant like pseudoephedrine or phenylephrine, or if used before breastfeeding is established.

Be sure to talk to your health care provider about all your choices for breastfeeding.

What if the father of the baby takes chlorpheniramine?
There is no evidence that suggests that a man’s chlorpheniramine use would cause any problems for conceiving or problems during 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 (https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/pdf/).

Selected References:

  • Aselton P, et al. 1985. First-trimester drug use and congenital disorders. Obstet Gynecol 65(4):451-455.
  • Diav-Citrin O, et al. 2003. Pregnancy outcome after gestational exposure to loratadine or antihistamines: a prospective controlled cohort study. J Allergy Clin Immunol 111(6):1239-1243.
  • Gilboa SM, et al. 2009. National Birth Defects Prevention Study: Use of antihistamine medications during early pregnancy and isolated major malformations. Birth Defects Res A Clin Mol Teratol 85(2):137-150.
  • Ito S, et al. 1993. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 168:1393-1399.
  • Jick H, et al. 1981: First-trimester drug use and congenital disorders. JAMA 246(4):343-346.
  • Li Q et al. 2013. Assessment of antihistamine use in early pregnancy and birth defects. J Allergy Clin Immunol Pract. 1(6):666-74.
  • Nelson MM and Forfar JJ.  1971. Associations between drugs administered during pregnancy and congenital abnormalities of the fetus. Br Med J. 1;523-527.