This sheet is about exposure to acyclovir or valacyclovir in a pregnancy or while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.
What is acyclovir?
Acyclovir is sold under the brand name Zovirax®. It is an antiviral medication used to treat cold sores and genital herpes caused by the herpes virus. It is also prescribed to treat chickenpox and shingles. It is given as a cream or ointment (topical use), oral tablets, or intravenous (IV) liquid. Acyclovir can help relieve the pain and help the healing of sores or blisters. It is not a cure for herpes and infections can return at a later time.
Is valacyclovir the same as acyclovir?
Valacyclovir is very similar to acyclovir and is often used to treat the same types of infections. It is sold under the brand name Valtrex®. Valacyclovir is changed to acyclovir once in a person’s body.
I take acyclovir/valacyclovir as needed to treat herpes. Can it make it harder for me to get pregnant?
It is not known if acyclovir/valacyclovir can make it harder to become pregnant.
I just found out I am pregnant. Should I stop taking acyclovir/valacyclovir?
Talk with your healthcare providers before making any changes to how you take your medication. The benefit of treatment should be weighed against the risks of untreated illness. Acyclovir/valacyclovir have been prescribed during pregnancy when the person has a primary genital herpes infection. A “primary” infection means it is the first time for the infection. Primary infection can be life threatening or lead to complications in a pregnancy. A rare but serious infection called varicella pneumonia might also require treatment with these medications.
Does taking acyclovir/valacyclovir increase the chance for miscarriage?
Miscarriage can occur in any pregnancy. Studies have not found an increased chance for miscarriage following acyclovir use.
Does taking acyclovir/valacyclovir increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Based on the information available, acyclovir/valacyclovir is not expected to increase the chance for birth defects.
The manufacturer, in combination with the Centers for Disease Control and Prevention (CDC), looked at the effects of acyclovir on the developing baby. No increase in birth defects was seen in over 500 births. Also, a separate study found no increase in birth defects in over 1,500 infants exposed to acyclovir and over 200 infants exposed to valacyclovir during the first trimester of pregnancy.
I have a cold sore on my lip. Could acyclovir ointment cause birth defects?
Topical use of acyclovir ointment is not expected to cause to increase the chance for birth defects. When applied on the skin, acyclovir does not enter the body in large amounts. Also, oral doses of acyclovir have not been associated with birth defects.
Can acyclovir/valacyclovir cause other problems during pregnancy?
The use of acyclovir/valacyclovir later in pregnancy has not been well studied. However, clinical experience has been reassuring.
Does taking acyclovir/valacyclovir in pregnancy cause long-term problems in behavior or learning for the baby?
It is not known if acyclovir/valacyclovir can cause behavior or learning issues.
Can I breastfeed while taking acyclovir/valacyclovir ?
Acyclovir enters breast milk in low amounts. Acyclovir is commonly given to newborns and does not typically cause problems for babies. If you are applying acyclovir cream or ointment directly on your breast, clean the area before nursing. Be sure to talk to your healthcare provider about all of your breastfeeding questions.
I take acyclovir. Can it make it harder for me to get my partner pregnant or increase the chance of birth defects?
Possible effects on sperm have not been well studied in fathers or sperm donors. One study in 20 males did not find lower sperm production when they were given high doses of acyclovir for six months. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
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OTIS/MotherToBaby recognizes that not all people identify as “men” or “women.” When using the term “mother,” we mean the source of the egg and/or uterus and by “father,” we mean the source of the sperm, regardless of the person’s gender identity.
