Do Flu Shots Affect Fertility or Pregnancy?

band aid for a flu shot during pregnancy
A well earned, flu-shot band aid (courtesy:

Its flu season. You’re trying to conceive or maybe you’re pregnant. Should you get a flu shot?

For those of you who never get the flu, here is the modern definition: A terrible sickness where you feel like you shouldn’t be able to walk, but somehow you can. For about a week, everything is achy and you get the WORST headache, a sore throat, a cough, a stuffy nose, a stomachache, and you sneeze and puke. Great. It happens to as many as 10 million to 50 million Americans annually.

Fertility and Flu Shots

Honest to goodness, there is really no science to suggest that flu shots affect male fertility. The same is true for female fertility. Not only that, flu shots are now being studied for their ability to increase pregnancy rates! Currently, two clinical trials are examining whether flu vaccines given outside of the flu season to infertile women undergoing IVF improve embryo implantation rates. Given the millions of flu shots given each year, it’s heartwarming to hear that there is no increased risk of infertility.

Flu Shots During Pregnancy

But what if you’re already pregnant? Is the flu shot safe here too? The short answer is yes. Although a single small study hinted that flu shots might be associated with higher miscarriage rates, the best data suggests otherwise. A well-done cohort study showed that when pregnant women receive flu shots, they are less likely to have premature births and low-birth-weight babies. Knowing all the evidence, the ever-vigilant CDC continues to strongly recommend that pregnant women get flu shots (but not with the live, attenuated virus).

Do I Need a Flu Shot During Every Pregnancy?

The amount of antibodies your body creates after getting vaccinated gradually decreases, and may not provide enough protection during future pregnancies. The Centers for Disease Control and Prevention recommend getting the flu shot each time you are pregnant.

Are There Any Side Effects From the Flu Shot?

Like any medicine, flu shots can have some side effects. The most common are redness, swelling and tenderness at the site of injection. Sometimes the muscles can ache at the injection site. However, most people do not experience side effects, or the side effects are very mild and temporary. 

If you have serious allergies, make sure you tell the person administering the shot.

The Flu and Fertility

A pretty convincing argument for getting a flu shot while trying to conceive or when pregnant comes from looking at what happens when you don’t get the shot. The flu is typically associated with fevers, and fevers kill sperm. So, male fertility is at risk. As the author of a hot bath study that showed the incredible effect of wet heat on sperm, I respect fevers! And, it’s a 3-month hit to a man’s fertility because that’s how long it takes to make a sperm. Infertile women with the flu may have a more difficult time conceiving as fevers interfere with the ability to track basal body temperatures that point to ovulation. So, flus can complicate conception for both sexes; better to avoid them entirely with flu shots.

The Flu and Pregnancy

In the setting of a growing bun in the oven, it’s well known that the flu can make women sicker than if they weren’t pregnant. Pregnancy alters the immune system and significantly stresses the heart and lungs, which can make the average flu much worse and lead to higher chances of being hospitalized. Flu fevers can also affect the developing baby, as they are associated with higher rates of neural tube defects and other adverse pregnancy outcomes.

Life is risky enough without the flu, so please do all you can to prevent it.