Vaccine and Menstrual cycles

It is time to talk about a huge elephant in my room. I took the covid-19 vaccine (Pfizer), and I have friends who did and friends who did not. I have heard a lot of reasons why to take and why not to take, and I took all of them into consideration when I decided to take the jab. I also took into consideration where I come from, my heritage, my privileges, my color, etc. But I will not enter those subjects today or ever, I will focus on the menstrual cycle in relation to vaccines.

It is known that science, therefore medicine, focused its studies on white male bodies. Most of the previous concepts in medicine, concepts we still use and acknowledge today, were written upon this specific person (white male). Female bodies and their reproductive system are usually not taken into account in most trials, and in vaccine trials as well.

Dr. Jen Gunter, gynecologist, proposes the following reflection: “Imagine if you didn’t know that fever could be a vaccine side effect?" We would all be concerned that something untoward was happening in our bodies. But that is a possible symptom that shows our body is fighting against the virus and building antibodies. That is the same with menstrual irregularities.

Unfortunately, according to Dr. Jen Gunter, menstrual cycles are not part of research when it comes to vaccines. Extremely heavy bleeding is probably followed closely but other minor changes in the cycles, as longer cycles, anovulatory, more intense cramps, or more intense bleeding than usual, are not taken into consideration. In my opinion, it is precise because of this that space is given to people to create conspiratory theories.

Another relevant point to make is that the cycle irregularities may occur differently depending on the phase you are in your menstrual cycle. For example, I took the covid-19 vaccine two days before I entered my menstrual phase, and I did not see any difference, maybe a little bit of difference in the flow but nothing that would make me worry, really! And if I had not taken the jab I probably would not even consider this a thing or a change in my menstruation.

We know that stress, infections, diseases, may interfere in our cycles. So the anxiety that pandemia may have caused or even the anxiety of going to take the vaccine could also promote a small change in our cycle. But let’s talk specifically about the covid-19 vaccine.

What are the symptoms one can experience in one's menstrual cycle after the covid-19 vaccine?

There are three ways the COVID-19 vaccine could potentially impact menstruation:

  • Impact on the chemical messaging from the brain to the ovaries;

  • Impact on the chemical messaging from the ovaries to the uterus;

  • The impact directly affects the lining of the uterus.

Let’s quickly recall how our menstrual cycle works: The brain signals to trigger follicles to start developing, the estrogen produced by the follicle builds the lining for the uterus. With ovulation the progesterone hormone is released, which signals the uterus to prepare for a possible pregnancy, in other words, the endometrium begins to grow to create a comfy bed for possible implantation. If there is no pregnancy, the progesterone is withdrawn and the endometrium “peels” and comes out as menstrual blood.

Therefore, the phase you are in your cycle when you take the vaccine will have a direct impact on the symptoms you might or might not experience. And recapturing, these symptoms might be experienced and not have a direct relation with the vaccine itself, because as said before other things may interfere in our menstrual cycle.

One important thing to take into consideration is how well we actually know our bodies and cycles. Because only with decent studies prior to vaccination, with women who were for at least three months prior following closely their cycles, it is possible to make a better conclusion on the impact of the covid-19 into our menstrual cycle.

As for the risk of abortions with the vaccine, there is no evidence that vaccination can lead to pregnancy losses, on the contrary, there are more and more studies suggesting that vaccination is safe and protects pregnant women from miscarriages, premature births, fetal and maternal death that can be triggered by COVID-19. I did read about very small research done in Spain, if I am not mistaken, claiming that in no studies the time of the pregnancy was taken into consideration to have a more clear view on if it is safe to take the vaccine in every stage of pregnancy. I totally respect this point but this research was made in a very questionable manner, including not revealing names of doctors who supported the claim, plus it is extremely important to conduct research following some basic research rules, otherwise, it is just to alarm and make people worry about something that was absolutely not proven.

There was another study published by the New England Journal of Medicine with more than 35,000 pregnant women vaccinated with mRNA technology vaccines (such as Pfizer and Moderna) and it showed no adverse events related to pregnancy when compared to the unvaccinated population. Other studies evaluated placenta health. In one, 84 placentas from women who received the COVID-19 vaccine were evaluated and did not observe negative changes in placental health compared to the control group. On the other hand, studies that evaluated the placental health of pregnant women who became infected with the COVID-19 virus showed that pregnant women had a higher risk of developing placental changes related to coagulation, which could put fetal health at risk.


I know we are all trying to choose the best for ourselves but we need to remember that vaccination is not about only me, it is about the collective. I wish I could talk more about the privilege there is in the decision not to take the vaccine because you know you most likely will not die because you live in a country with a great health care system and you will not die in the line waiting for a bed. This is the reality of several countries, countries that are beautiful with great culture and history, countries that a lot of people from the first world would love to spend a vacation in. Imagine if they are not vaccinated and you bring the virus to them while passing by? They do not have a choice. The vaccine is saving their lives. Being able to choose is the definition of privilege in the middle of a global pandemia.






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