This sheet is about exposure to respiratory syncytial virus (RSV) in pregnancy or while breastfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

What is respiratory syncytial virus (RSV)?

Respiratory syncytial virus (called RSV) can cause an infection of the respiratory (breathing) tract. Having the infection is also commonly called RSV.

RSV is a common infection. It often causes cold-like symptoms. Babies, adults who are older, and people with a weakened immune system have a higher chance of getting severe symptoms, including lower respiratory disease and pneumonia. People with severe symptoms may need to be treated in a hospital. It is not known if people who are pregnant have a higher chance of developing severe symptoms.

In most regions of the United States, RSV season generally starts during fall and peaks in the winter. However, the timing and severity of RSV seasons can be different from year to year.

Is RSV contagious? How does the virus spread?

RSV spreads easily from person to person when someone who is infected with the virus coughs or sneezes. RSV can also be spread through direct contact with people who are sick (shaking hands or kissing) or touching surfaces that have the virus on them. Close contact with young children, such as in daycare settings, is a common way to become infected with RSV.

People infected with RSV usually show symptoms within 4 to 6 days after getting infected, but some people might not have symptoms (asymptomatic).

People with RSV may be contagious 1 or 2 days before symptoms would start, and most people are contagious for 3 to 8 days after symptoms would start. However, some infants, and people with weakened immune systems, can still spread the virus for up to 4 weeks after they stop showing symptoms.

I have an RSV infection. Can it make it harder for me to get pregnant?

Studies have not been done to see if having an RSV infection could make it harder to get pregnant.

Does having RSV increase the chance for miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. One study reported that RSV was more common among people who had a miscarriage compared to people who did not have a miscarriage. However, other reports did not notice a higher chance for miscarriage. As there can be many causes of miscarriage, it is hard to know if the infection, medication, or other factors are the cause of a miscarriage.

Does having RSV 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.

RSV infection in pregnancy is not well-studied. However, RSV is not expected to increase the chance for birth defects above the background risk.

Would having RSV increase the chance of other pregnancy related problems?

In reports of RSV in pregnancy, pregnancy complications such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth) were not common. In reports when a pregnancy complication was reported, many of those people also had another medical condition or infection.

If I have RSV during my pregnancy, can the infection pass to the fetus?

Studies have suggested that it is possible to pass an RSV infection to the fetus across the placenta. One small study reported that newborns born to people who had RSV during the third trimester could have some breathing problems related to RSV.

Does having RSV in pregnancy affect future behavior or learning for the child?

Studies have not been done to see if RSV infection in pregnancy can cause behavior or learning issues for the child.

How can I protect myself and my baby?

There is an RSV vaccine for people to take between 32 and 36 weeks of pregnancy to help reduce the chance of the newborn getting severe RSV symptoms. MotherToBaby has a fact sheet on the RSV vaccine at: https://mothertobaby.org/fact-sheets/rsv-vaccine/.

In addition to getting the RSV vaccine, be sure that you and others around you are doing the following to help prevent spread of viruses:

• Wash your hands with soap and water often or use an alcohol-based hand sanitizer if soap and water are not available.
• Cover your nose and mouth when you cough or sneeze and ask those around you to do the same.
• Do not touch your eyes, nose, or mouth.
• Try to avoid close contact with people who are sick.
• Do not share drinking glasses or eating utensils with others.
• Clean touched surfaces such as doorknobs, toys, and mobile devices.

Breastfeeding while I have RSV:

People are encouraged to continue to provide breast milk for their babies even if they have RSV. People who currently have RSV or had RSV in pregnancy might pass protective immunity factors to the infant through breastmilk. This might reduce the chance of RSV or the chance of developing severe RSV symptoms in a newborn. Be sure to talk to your healthcare provider about all your breastfeeding questions.

While sick, it is important to try to protect the baby from the virus. Wash hands with soap and water before holding your baby. Avoid coughing or sneezing on your baby. Cover your mouth/nose with a tissue when you cough or sneeze, then throw away the tissue and wash your hands.

If a male has RSV, can it make it harder to get a partner pregnant or increase the chance of birth defects?

Studies have not been done to see if RSV could affect male fertility (ability to get partner pregnant) or increase the chance of birth defects above the background risk. Close contact may not be recommended when you have RSV to try to avoid passing RSV to your partner. For more general information on paternal exposures, please see the MotherToBaby fact sheet at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.

Selected References:

• Bokun V, et al. 2019. Respiratory Syncytial Virus Exhibits Differential Tropism for Distinct Human Placental Cell Types with Hofbauer Cells Acting as a Permissive Reservoir for Infection. PloS One; 14(12):e0225767. [PMC free article: PMC6886783] [PubMed: 31790466]
• Centers for Disease Control and Prevention (CDC). 08/2023. Respiratory Syncytial Virus Infection (RSV) web page: https://www​.cdc.gov/rsv/index.html [Accessed 8/2023].
• Chu HY, et al. 2016. Clinical Presentation and Birth Outcomes Associated with Respiratory Syncytial Virus Infection in Pregnancy. PLoS One. 2016 Mar 31;11(3):e0152015. [PMC free article: PMC4816499] [PubMed: 27031702]
• Chiba Y, et al. 1987. Effect of breast feeding on responses of systemic interferon and virus-specific lymphocyte transformation in infants with respiratory syncytial virus infection. J Med Virol; 21(1):7-14. [PubMed: 3794673]
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