Yes, getting the flu shot while pregnant is safe. Major health organizations recommend it during any trimester, and decades of safety data from hundreds of thousands of pregnancies back that up. The vaccine protects both you and your baby, since newborns can’t get their own flu shot until they’re six months old.
What the Safety Data Shows
The CDC’s Vaccine Safety Datalink, one of the largest vaccine monitoring systems in the country, has studied the flu shot in pregnancy across multiple flu seasons and found no increased risk of miscarriage. A separate study within the same system found no increased risk of stillbirth among vaccinated pregnant women. And a 2017 analysis found that babies born to women vaccinated during their first trimester had no higher rate of major birth defects.
Researchers have also looked at whether the flu shot raises the chance of preterm delivery, low birth weight, pre-eclampsia, or other obstetric complications. Across studies covering flu seasons from 2002 through 2015, vaccinated and unvaccinated pregnant women had the same rates of these outcomes.
Side Effects Are the Same as for Anyone Else
Pregnant women experience the same mild side effects as the general population. The most common are soreness or redness at the injection site, headache, muscle aches, mild fever, nausea, and fatigue. These typically start within hours of the shot and resolve in one to two days.
How the Flu Shot Protects Your Baby
When you get vaccinated during pregnancy, your body produces antibodies that cross the placenta and reach your baby. This gives your newborn a head start on flu protection during the vulnerable months before they’re old enough for their own vaccine.
A large Kaiser Permanente study found that maternal flu vaccination was linked to a 44% reduction in infant flu cases during the first six months of life. Protection was strongest in the earliest weeks: a 51% reduction in flu risk for babies under two months old, and 56% for babies between two and four months. After four months, protection dropped to about 29% as the transferred antibodies naturally faded.
The benefits were even more striking for severe illness. Getting vaccinated during pregnancy cut the risk of flu-related hospitalization in infants under six months by roughly 40%, and the risk of emergency department visits by about 20%. Among babies younger than three months, the vaccine cut the risk of hospitalization or emergency visits in half.
Timing Matters for Your Baby’s Protection
You can safely get the flu shot during any trimester, but timing affects how much protection passes to your baby. Vaccination during the third trimester was associated with a 59% reduction in infant flu during the first six months, compared to about 52% for second-trimester vaccination. That makes sense: getting the shot closer to delivery means your antibody levels are at their peak right when your baby is born.
That said, the most important thing is getting vaccinated before flu season, regardless of which trimester you’re in. If flu season arrives while you’re in your first or second trimester, don’t wait. Protecting yourself from flu complications during pregnancy matters just as much as protecting your baby after birth.
One Type of Flu Vaccine to Avoid
The injectable flu shot (the standard shot in the arm) is the recommended form during pregnancy. The nasal spray vaccine, FluMist, is not approved for pregnant women because it contains a weakened live virus. This applies even though FluMist recently became available for self-administration at home. If you’re pregnant, stick with the shot.
Thimerosal-Free Options for 2025-2026
For the 2025-2026 flu season, the CDC specifically recommends that pregnant women receive thimerosal-free, single-dose flu vaccines. Thimerosal is a mercury-based preservative used in multi-dose vaccine vials. While no evidence links thimerosal in vaccines to harm during pregnancy, the shift to preservative-free formulations for pregnant women reflects a precautionary approach. These single-dose versions are widely available at pharmacies and doctor’s offices.
All flu vaccines this season are trivalent, meaning they protect against three strains of influenza. Public health officials have flagged a newly circulating strain of H3N2 that has drifted from the vaccine’s H3N2 component, which could reduce effectiveness against that particular strain. Even with reduced effectiveness against one strain, vaccination still provides meaningful protection, especially against severe illness.
Why the Flu Is Riskier During Pregnancy
Pregnancy naturally shifts your immune system and changes your heart and lung function. These changes make you more vulnerable to severe flu complications, including pneumonia and hospitalization. Flu during pregnancy is also associated with higher rates of preterm labor and other complications. The flu shot significantly reduces the chance of these outcomes, protecting you while your body is doing the already demanding work of growing a baby.