Medically reviewed by references to CDC and ACOG guidelines.
Influenza (the flu) is more than just a bad cold, it can be a serious health threat, especially for expectant mothers. If you are pregnant or planning to become pregnant, understanding the importance of the flu vaccine is crucial for your health and the well-being of your baby.
This guide explains why medical experts, including the Centers for Disease Control and Prevention (CDC), strongly recommend the flu shot during pregnancy, addresses common safety concerns, and reviews the extensive research supporting its use.
Why is the Flu Shot Critical During Pregnancy?
Pregnancy causes changes in the immune system, heart, and lungs. These physiological changes make pregnant women more likely to develop severe illness from influenza that may require hospitalization compared to non-pregnant women of reproductive age.
Furthermore, the flu can harm the developing baby. A common symptom of influenza is fever, which has been associated in some studies with neural tube defects and other adverse outcomes for the unborn baby.
Protection for the Newborn:
Getting vaccinated while pregnant isn’t just about protecting yourself. When you get the shot, your body produces protective antibodies (proteins that fight infection) that you pass directly to your baby during pregnancy. This provides the new-born with crucial protection against the flu for the first several months of life, a time when they are too young to be vaccinated themselves.
Is the Flu Vaccine Safe for Pregnant Women and Their Babies?
Yes. Injectable flu vaccines have been given to millions of pregnant women for decades and have an excellent safety record. There is a large body of scientific evidence supporting the safety of the flu vaccine for both pregnant women and their babies.
The CDC and the Advisory Committee on Immunization Practices (ACIP) recommend flu vaccination during any trimester of pregnancy. Pregnant women should receive the flu shot (inactivated vaccine) and not the nasal spray flu vaccine (LAIV), which contains a live attenuated virus.
Addressing the Miscarriage Question — What Does the Research Show?
It is natural to have questions about pregnancy and medication safety. One of the most common concerns is whether the flu shot can cause a miscarriage.
The Short Answer: Multiple large-scale studies have confirmed that the flu shot does not increase the risk of miscarriage.
The Science and the “Safety Signal” (The VSD Study):
The Vaccine Safety Datalink (VSD) a collaboration between the CDC and several health care organizations is a key tool used to monitor vaccine safety . This system allows researchers to conduct robust, ongoing studies.
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The Initial Finding: A smaller, early study (looking at the 2010-11 and 2011-12 flu seasons) suggested a possible association between miscarriage and flu vaccination in early pregnancy, specifically among women who had also been vaccinated the previous year. However, this study had significant limitations, including a small sample size, which could have led to inaccurate results.
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The Definitive Follow-Up: Because this initial finding raised a question, the CDC funded a much larger, more rigorous follow-up study using the VSD. This critical study spanned three flu seasons (2012-13, 2013-14, and 2014-15) and enrolled three times as many women. The results were clear: The study found no increased risk of miscarriage associated with influenza vaccination during pregnancy.
In response to the initial “safety signal,” the robust follow-up study confirmed the safety of the vaccine. The CDC, ACOG, and ACIP continue to recommend the flu shot because the proven dangers of the flu far outweigh any unproven risks.
What Side Effects Can Pregnant Women Expect?
The side effects of the flu shot for pregnant women are generally mild and the same as those for anyone else. These usually begin soon after the shot and last for 1-2 days:
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Soreness, redness, or swelling at the injection site
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Headache
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Fever
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Muscle aches
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Nausea
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Fatigue
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Fainting (occasionally, as with any injection)
Serious problems, such as severe allergic reactions, are rare. Anyone with a severe, life-threatening allergy to any ingredient in the vaccine should not receive it.
Special Considerations
Can pregnant women with an egg allergy get the flu shot?
Yes. Pregnant women with egg allergies of any severity can receive any licensed, recommended, and age-appropriate flu shot. Previous recommendations for additional safety measures or monitoring periods beyond those recommended for any vaccine are no longer needed. However, all vaccines should be given in settings where allergic reactions can be recognized and treated quickly.
What about Thimerosal?
Some flu vaccines are produced in multi-dose vials that contain thimerosal (a preservative that prevents contamination). Extensive studies have shown that the small amount of thimerosal in vaccines does not cause harm . However, thimerosal-free (single-dose) flu vaccines are available for those who wish to request them.
Can breastfeeding women get the flu vaccine?
Absolutely. Women who are breastfeeding should get the flu vaccine. This protects the mother from getting sick and reduces the risk of passing the flu to her infant. The antibodies produced by the mother are also shared through breast milk, offering additional protection to the baby.
How is the Safety of Flu Vaccines Monitored?
The CDC and the FDA continuously monitor the safety of all vaccines. They use two main systems:
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Vaccine Adverse Event Reporting System (VAERS): An early warning system where anyone can report health problems that occur after vaccination. It helps detect potential safety signals that need further investigation.
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Vaccine Safety Datalink (VSD): A collaboration between the CDC and several health care organizations that conducts rigorous, proactive research on vaccine safety, like the large miscarriage study mentioned above.
Summary of Key CDC Studies on Safety
Numerous studies by the CDC and its partners support the safety of the flu vaccine during pregnancy:
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Birth Defects: A large 2017 VSD study found that babies of women vaccinated during the first trimester had no increased risk of major birth defects.
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Preterm Birth: A VSD study found no difference in rates of premature delivery or small-for-gestational-age infants between vaccinated and unvaccinated mothers.
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Obstetric Events: Another VSD study found no increased risk of adverse events like chorioamnionitis or pre-eclampsia in vaccinated women.
Conclusion
The influenza vaccine is a safe, effective, and essential tool for protecting pregnant women and their babies. With over 50 years of safety data and ongoing monitoring by the CDC through systems like the Vaccine Safety Datalink (VSD) , expectant mothers can feel confident in getting the flu shot.
Talk to your healthcare provider about getting the flu vaccine to ensure a healthier flu season for you and your little one.
