The arrival of flu season often raises questions among women who are trying to conceive, particularly those undergoing assisted reproduction treatment. Is it safe to be vaccinated? Could it affect follicular development, implantation, or the course of pregnancy? Below, we address the most frequently asked questions in a clear and evidence-based manner.
Can I get the flu shot if I'm trying to get pregnant or currently in treatment?
Yes. The flu vaccine is completely safe for women attempting to conceive naturally and for those undergoing treatments such as IVF/ICSI, egg donation, or artificial insemination.
It is an inactivated vaccine, meaning it contains no live virus and cannot cause infection or interfere with fertility.
Can the vaccine affect my eggs, ovarian reserve, or ovulation?
No. Evidence shows that the flu vaccine does not affect egg quality, response to stimulation, or ovarian reserve. It also does not alter ovulation or hormone levels.
In short: it does not make it harder to become pregnant.
Is it preferable to get vaccinated before starting IVF? What if I have already begun?
It is generally advisable to be vaccinated before beginning treatment, particularly before starting ovarian stimulation or endometrial preparation. This is not because the vaccine influences the outcome—it does not—but to avoid possible discomfort (fever, muscle pain, fatigue) at a time when your body needs to be in optimal condition.
If you have already started stimulation or endometrial preparation, the recommendation is to wait until that phase is complete and then be vaccinated.
In any case, if you need to be vaccinated earlier for medical reasons, it does not pose a risk to the treatment. However, if you have the option, it is preferable to avoid vaccination during stimulation or endometrial preparation.
What happens if I get vaccinated right after the embryo transfer?
Nothing of concern. You may do so safely.
The vaccine does not interfere with implantation, does not alter the endometrium, and does not increase the risk of miscarriage. If the vaccination campaign coincides with those days, there is no need to wait for the pregnancy test.
Can I receive the flu vaccine if I am already pregnant?
Yes. In fact, major scientific societies recommend it during any trimester of pregnancy.
The reason is straightforward: during pregnancy, the immune system changes, and flu-related complications can be more severe. Vaccination protects you—and also protects the baby during the first months of life, as antibodies pass through the placenta.
Can the vaccine cause fever? Would that affect pregnancy or treatment?
The vaccine may cause mild discomfort, such as local pain or slight fever. Although these reactions do not directly affect fertility or the embryo, it is preferable to avoid fever during ovarian stimulation or endometrial preparation, phases in which we aim to keep the body as stable as possible.
If you are between phases or have not yet begun treatment, you may be vaccinated with complete confidence. And if you are already pregnant, a mild fever after vaccination does not pose a risk to the pregnancy.
Should my partner be vaccinated as well?
It is not mandatory, but it is recommended. Maintaining a protected environment helps reduce the risk of infection during particularly sensitive moments, such as stimulation or the period following embryo transfer.
What if I was vaccinated without knowing I was pregnant?
Nothing at all. This is relatively common and does not pose any risk to the embryo.
Conclusion
Flu vaccination is safe, recommended, and does not affect fertility. It can be administered before starting assisted reproduction treatment and also between phases, although it is preferable to avoid it during ovarian stimulation and endometrial preparation to prevent possible discomfort or mild fever during key moments of the process.
During pregnancy, the vaccine is recommended in any trimester, as it protects both the mother and the baby during the first months of life.