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 2009 H1N1 flu 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 the 2009 H1N1 flu?

The flu (more formally known as influenza) is an infection of the respiratory (breathing) tract. During the 2009-2010 flu season, people got sick from both seasonal flu viruses and a new type of flu virus called H1N1. The H1N1 flu first appeared in the United States in April 2009. Since few people had any immunity to it, H1N1 spread from person to person around the world, even during summer months, and was therefore known as a pandemic flu. While the pandemic has been declared over, the H1N1 virus is still expected to continue to make people sick for many years. The symptoms of the H1N1 flu are similar to those seen with seasonal flu. You may have fever, headache, chills, muscle aches, coughing, congestion, runny nose, and sore throat. Sometimes H1N1 flu can cause stomach upset with vomiting and diarrhea.

Is H1N1 flu the same as the swine flu?

The H1N1 flu was originally called “swine flu” because the virus was found to be similar to viruses causing illness in pigs. However, it is now known that H1N1 contains parts of viruses found in pigs, birds, and people. H1N1 flu is spread from person to person. You cannot get H1N1 flu by eating pork or pork products.

Is H1N1 flu contagious? How does the virus spread?

Yes, H1N1 flu is contagious. The virus is spread from person to person in the same way that seasonal flu viruses are spread. Respiratory droplets containing the virus are spread through the air when people cough or sneeze. A person with the H1N1 flu is contagious for up to a week after he or she first develops symptoms.

How severe is H1N1 flu?

Illness from H1N1 flu ranges from mild to severe. Most people who get sick will recover without needing any medical treatment. However, there have been cases of hospitalizations and deaths from H1N1 flu. Unlike seasonal flu, the chance of catching H1N1 is highest in people who are less than 65 years old. Young children, pregnant women, people with underlying medical conditions, and those over age 65 are all at increased risk for severe complications from H1N1 flu.

I have heard that pregnant women can get sicker than other people from the H1N1 flu. Is this true?

Yes. When you are pregnant your body has a harder time fighting infections. Pregnant women have an increased risk of developing serious complications from the H1N1 flu, such as respiratory distress (severe breathing problems). Severe disease, hospital admissions, and even death have occurred in pregnant women who had the H1N1 flu. Serious complications have occurred in all trimesters and some women with severe disease had no other health problems other than the H1N1 flu.

Can having the H1N1 flu during pregnancy cause birth defects or put my baby at risk?

Since H1N1 is a new type of influenza virus, we do not yet have studies looking at the babies born to women who had H1N1 flu during pregnancy. However, other types of influenza viruses have not been shown to cause birth defects.

Having a high fever during pregnancy may increase the risk for birth defects. Therefore, fever during pregnancy should be treated. Acetaminophen is the drug of choice for reducing fever during pregnancy. Tylenol® is one brand of acetaminophen.

Being very sick from the flu may increase the risk of pregnancy complications such as miscarriage or premature delivery. It is important to talk with your health care provider if you are pregnant and have symptoms of the flu.

How can I prevent getting the H1N1 flu?

Getting vaccinated is the best way to protect yourself and your baby. The H1N1 vaccine was available during the 2009-2010 flu season as a separate vaccine. Starting in the 2010-2011 flu season, the seasonal flu shot will provide protection against seasonal and H1N1 flu viruses. An additional H1N1 flu shot is no longer needed.

The injected form of the influenza vaccine (flu shot) is recommended during any trimester of pregnancy. The nasal-spray influenza vaccine is not recommended during pregnancy. Getting vaccinated during pregnancy can also help protect your baby from getting sick during the first six months of life when the baby is too young to be vaccinated. For more information about the influenza vaccine, see the MotherToBaby fact sheet Seasonal Influenza Vaccine (Flu Shot) during Pregnancy at

In addition to getting the flu vaccine, 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.

What should I do if I get sick?

If you have flu-like symptoms, talk to your health care provider right away. Your health care provider may recommend antiviral medications to lessen the symptoms of the flu and to reduce the risk of serious illness. These medications work best if taken early in the course of the illness. For more information about antiviral medications, see the MotherToBaby fact sheet Antiviral Medications to Treat/Prevent Influenza during Pregnancy at If you are sick, stay home and avoid close contact with others to prevent passing the illness to other people. Be sure to drink plenty of fluids. Treat fever right away with acetaminophen (Tylenol®).

Should I talk to my health care provider if one of my family members is sick?

Yes. Talk with your health care provider if you have been in close contact with someone who has H1N1 flu. Pregnant women are at an increased risk for complications from the H1N1 flu. Some women may benefit from taking antiviral medications 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.

Should I stop breastfeeding if I have the H1N1 flu?

No. Breastfeeding provides the best nutrition for your baby, and there are antibodies in your breast milk that may help prevent your baby from getting sick.

It is important to try to protect your baby from getting sick. Wash your hands with soap and water before holding your baby. Avoid coughing or sneezing on your baby. Consider wearing a mask over your nose and mouth while feeding and caring for your baby to help prevent you passing the illness to your baby. While you are ill, you may want to consider having a family member who is not sick help you with caring for your baby.

If your baby has the flu, it is especially important to breastfeed as often as possible. Your baby will need extra fluids during this time. Your milk is better for this than anything else, even than things like Pedialyte®. Also, antibodies in your milk help your baby fight the infection and get better faster. Be sure to talk to your health care provider about all your choices for breastfeeding.

MotherToBaby is currently conducting the Vaccines and Medications in Pregnancy Study (VAMPSS). The purpose of the study is to learn more about influenza vaccines and antiviral medication use in pregnancy. If you are pregnant and have received the influenza vaccine or have taken an antiviral medication to prevent or treat the flu (including Tamiflu® or Relenza®), and you are interested in learning more about this study, please contact the VAMPSS Coordinating Center at 877-311-8972.

References Available By Request