Many women, when pregnant, worry about everything that enters their body. Concerns about their diet and medications run rampant. This is especially true when it comes to one hotly debated topic: the seasonal flu shot.
The flu shot is considered an important part of prenatal care, and the American College of Obstetricians and Gynecologists calls it "an essential element of pre-pregnancy, prenatal, and postpartum care" and calls on “all obstetrician–gynecologists and all providers of obstetric care [to] advocate for influenza vaccination and provide [it] to their pregnant patients.” Changes in a woman’s immune system, heart, and lungs during pregnancy make her more susceptible to infection. Even women in good health prior to pregnancy and with a history of mild flu symptoms are at risk of serious illness should they become sick with the flu during pregnancy. A study of hospitalizations during the 2009–2010 H1N1 flu pandemic in Washington State found that pregnant women were more likely to need hospital care compared to non-pregnant flu patients, particularly in the Intensive Care Unit (ICU). A similar study from the 2013–2014 flu season in California reached the same conclusion. Pregnant women benefit most from the flu vaccine, and they should receive antiviral medication promptly if one suspects they have the flu.
A pregnant woman’s flu shot is also considered an important part of newborn care.Babies can’t be given flu vaccines until they are 6 months old (and they aren't fully vaccinated until a second dose is given, a month after the first), but a pregnant woman can pass immunity to her baby in the form of antibodies.
The flu vaccine also reduces the infant’s risk of exposure to the virus; a mother who is less likely to get the flu herself is less likely to pass it along to her child. (For this same reason, fathers and others who will interact with the newborn child should also receive a flu vaccination. Learn more about how to protect an unvaccinated baby here.)
Therefore, the CDC urges all women who will be pregnant during flu season to get a flu shot in any trimester—but not the nasal spray flu vaccine, which should be avoided during pregnancy since it contains live virus. The shot contains inactivated (dead) virus, and is considered safer during pregnancy.
Opting out of the flu vaccine
Some pregnant women express concerns that the flu vaccine might increase their risk of miscarriage. To the contrary, according to the CDC, pregnant women who receive the flu vaccine during the first trimester are less likely to experience miscarriage than women who did not. It is the influenza that increases risks for miscarriage, as well as preterm birth and low birthweight. The 2009–2010 Washington state study found lower rates of miscarriage among women who had a seasonal flu shot. Other studies have shown lower risks for preterm birth, small-for-gestational-age babies, and infant mortality among women who received the influenza vaccine.
Some pregnant women are concerned about the presence of thimerosal, a mercury-containing organic compound used as a preservative to prevent the growth of microbes in vaccines and has been linked to autism. The CDC points out that research has not shown a causal link. Rates of autism continue to rise even though thimerosal has been removed from all vaccines except the multi-dose flu vaccine. Still, it should be easier than ever for pregnant women to find thimerosal-free vaccines. According to the CDC, two-thirds of flu vaccine doses available in the U.S. are single-dose vials—which do not contain thimerosal—and that rate is increasing every year. Ask your health care provider if a single-dose vial is available. If it is not, the CDC emphasizes that the small amount of thimerosal present in the influenza vaccine poses no health risks and urges all pregnant women to get a flu shot for the important protection it provides.
Some women may be concerned about the flu vaccine due to egg allergy. The CDC recommends that people with an egg allergy who have had a "hives only" reaction can get the flu shot without post-vaccination follow-up. Those with a severe egg allergy, such as one that has resulted in hives and additional symptoms, should be vaccinated in a medical setting by a health care provider who is able to recognize and manage allergic response. The only individuals advised to avoid getting a flu shot are those with a history of serious reactions (anaphylaxis) to the flu vaccine.
It is important to remember that there are many different types and strains of flu virus. Each flu season, different types and strains circulate. Scientists try to determine which strains are likely to circulate in any given year and produce vaccines based on their predictions. According to the CDC, even if the vaccine is “less than an ideal match,” it can still protect against other viruses. However, pregnant women should be aware that even if they have had a flu shot, they can still get infected with other types of flu virus. Pregnant women are urged to call their doctor right away if they develop any flu-like symptoms. Early treatment with an antiviral medication is important for the mother’s health, and the health of her baby.