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 antiviral medications 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 are antiviral medications and what do they do?

Antiviral medications are used to treat viral, not bacterial, illnesses. An example of a viral illness is influenza (the “flu”). Antiviral medications can lessen the symptoms of the flu and reduce the risk of serious illness. Some of these medications may also be used to prevent a person from catching the flu. Symptoms may include fever, headache, chills, muscle aches, coughing, congestion, runny nose, and sore throat. Some people can also have stomach upset with vomiting and diarrhea.

Which antiviral medications are used to treat or prevent the flu?

Oseltamivir (Tamiflu®), peramivir (Rapivab®) and zanamivir (Relenza®) are the antiviral medications used for influenza prevention and treatment. Amantadine (Symmetrel®) and rimantadine (Flumadine®) are two other antiviral medications, but they are not recommended anymore because of resistance concerns.

Can I skip getting the flu vaccine during my pregnancy and just take one of these medications if I happen to get sick?

No. Antiviral medications are not a substitute for the flu vaccine. Pregnant women are at an increased risk for complications from the flu. Women who are pregnant or planning to become pregnant should get the injected form of the flu vaccine (flu shot). The nasal-spray form of the influenza vaccine is not recommended during pregnancy. For more information, see the MotherToBaby fact sheet on the Seasonal Influenza Vaccine (Flu Shot) at

Can taking antiviral medications make it harder for me to get pregnant?

It is unclear. There are no studies that look at the fertility in women taking an antiviral medication.

I stopped taking an antiviral medication about one month before I became pregnant. Was my baby exposed to this medication?

While it can vary from person to person, the antiviral medications listed in this fact sheet are generally gone from the body by seven days after the last dose. If you are taking one of these medications and find out that you are pregnant, talk with your health care provider to decide what to do with your treatment.

Does taking an antiviral medication increase the risk for miscarriage?

Researchers did not find a higher risk of miscarriage following the use of oseltamivir. The risk of miscarriage has not been evaluated for other antiviral medications.

Can taking an antiviral medication during pregnancy cause a birth defect?

Current information indicates that some antiviral medications do not increase the risk for birth defects. However, the information is more limited than for other medications.

Several studies that looked at oseltamivir or zanamivir use during pregnancy did not find an increased risk for birth defects for either medication.

Information on peramivir is too limited to evaluate its safety during pregnancy.

Limited information from animal and human studies does not suggest an increased risk for birth defects or pregnancy complications when amantadine or rimantadine are used in pregnancy.

Can taking antiviral medication during pregnancy cause pregnancy complications?

No. Several studies found no higher risk pregnancy complications when women had been treated with oseltamivir or zanamivir during pregnancy. Less information is published for other antiviral medications.

I am pregnant and think I may have the flu. Should I talk to my health care provider about antiviral medication?

Yes. You should talk to your health care provider as soon as possible. Pregnant women are at an increased risk for complications from the flu. Some of these complications can put both the mother’s and her developing baby’s health at serious risk. Taking an antiviral medication within 48 hours (the earlier the better) of your first symptoms can reduce the chance that you will have severe complications. The medication may still be helpful when they are started later than this, so talk to your health care provider even if you have already been sick for more than 2 days. For current recommendations regarding prevention and treatment of flu with antiviral medications during pregnancy, visit the Centers for Disease Control and Prevention (CDC)’s website at

I am pregnant and my husband has the flu. Should I take oseltamivir so that I don’t get sick?

Talk with your health care provider if you have been in close contact with someone who has the flu. Because pregnant women are at an increased risk for complications from the flu, some women may benefit from taking antiviral medications, usually oseltamivir or zanamivir, to prevent getting the flu after they have been exposed. Your health care provider can help you decide whether taking an antiviral medication for flu prevention is best for you. Depending on your condition, your health care provider may suggest to start an early treatment only if you have symptoms of flu instead of taking an antiviral to prevent infection.

Be sure that you and others around you are doing the following to help prevent spread of the flu:

  • Wash your hands with soap and water frequently
  • Avoid touching your eyes, nose, or mouth
  • Try to avoid close contact with sick people
  • Cover your nose and mouth when you cough or sneeze
  • Stay home and avoid close contact with others if you are sick

I am breastfeeding and have just come down with the flu. Can I take one of the antiviral medications to shorten the number of days that I will be sick?

Oseltamivir is found in breast milk in very low amounts and is not likely to be harmful to the breastfed infant. Zanamivir is given by inhalation. This limits the amount of the medication that gets into your bloodstream. For this reason, zanamivir is unlikely to enter breast milk in high amounts and would not affect a breastfed infant. There have been no studies looking at the use of peramivir during breastfeeding. Because peramivir is poorly absorbed from the gut, it is unlikely that the medication that gets into breast milk would enter the baby’s system. There are no studies looking at amantadine and rimantadine during breastfeeding. It may be best to avoid using amantadine or rimantadine while breastfeeding since they may reduce milk supply. Be sure to talk to your health care provider about all your breastfeeding questions.

Is there a concern if my partner was taking an antiviral medication when I got pregnant?

In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures and Pregnancy at

References Available By Request