Date: July 2022, Version 3.1

Quick read

Aciclovir can be used in pregnancy and is the first-choice treatment for cold sores, genital herpes and, occasionally, chickenpox.

What is it?

Aciclovir cream (Zovirax®) is used to treat cold sores and can be bought over the counter. Aciclovir in tablet form is used to treat and prevent genital herpes and chickenpox.


What are the benefits of using aciclovir in pregnancy?

Aciclovir cream can help to speed up healing of cold sores and reduces symptoms such as burning and pain.

Aciclovir tablets can prevent genital herpes from flaring during later pregnancy and being passed on to the baby during delivery.

Aciclovir tablets can also reduce the severity of a chickenpox infection. Treatment with aciclovir can also reduce the risk of a pregnant woman who has not had chickenpox from developing the illness following contact with an infected person.


What are the risks of using aciclovir in pregnancy?

There are no known risks of using aciclovir in pregnancy. Aciclovir cream does not enter the bloodstream in levels that are high enough to affect the baby.


Are there any alternatives to using aciclovir in pregnancy?

Possibly. Other antiviral medicines are available but aciclovir is usually the first-choice in pregnancy as it is considered to be the safest option.

Some women may choose not to treat uncomplicated facial cold sores in pregnancy and these usually get better within a few days.

Paracetamol can be used to safely treat symptoms that may be linked to a cold sore, including achy joints, a temperature, and pain.

No treatment

What if I prefer not to take medicines during pregnancy?

Use of aciclovir in pregnancy for genital herpes can reduce the chance of preterm delivery and prevent the baby catching herpes during delivery, which can lead to serious complications.

Use of aciclovir to treat or prevent chickenpox is important because chickenpox can cause complications in adults and, especially in early pregnancy, can harm the unborn baby.

A doctor or midwife will be happy to discuss any concerns about using aciclovir in pregnancy.

Will my baby need extra monitoring?

As part of routine antenatal care in the UK, women are invited for a very detailed scan at around 20 weeks of pregnancy to check the baby’s development. Using aciclovir in pregnancy is not expected to cause problems that would require any extra monitoring.

Are there any risks to my baby if the father has taken aciclovir?

We would not expect any increased risk to the baby if the father used aciclovir before or around the time of conception.

Who can I talk to if I have questions?

If you have any questions about the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.