COVID-19 vaccination and pregnancy

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The big question

Will the COVID-19 vaccine affect my fertility?

The quick answer

No.

The current data and scientific studies indicate that the COVID-19 vaccines do not affect your ability to become pregnant or your ability to carry a pregnancy to term.

The research also shows that these vaccines are safe to receive during pregnancy, as there is no evidence of increased risk for pregnancy complications or pregnancy loss associated with the vaccines.

In fact, experts recommend vaccination, whether you are pregnant now (any trimester) or you are planning to become pregnant in the future—in part because becoming sick with COVID-19 during pregnancy can be risky.

If you have questions or would like to discuss the best options for you, please don’t hesitate to talk to your health care provider.

Note: The information provided here is derived primarily from studies involving the mRNA-based COVID-19 vaccines (Pfizer/BioNTech and Moderna).

Read more about the general benefits of vaccination, how mRNA vaccines work, and great ways to deal with needle pain and fear.

The longer story

Pregnancy can be nerve-wracking—and that was true long before the pressures of a global pandemic were added to the experience. If you are currently pregnant, planning or trying to become pregnant, or maybe just thinking it could be something you’ll want to consider someday, you probably have questions about COVID-19 vaccines and pregnancy (or future fertility). And that’s perfectly reasonable!

Unfortunately, misinformation about COVID-19 vaccines and fertility has been rampant, leading to a lot of stress, fear, and confusion.

While unfounded rumours will continue to pop up online, the good news is that data from scientific studies around the world have been very reassuring. There is already a tremendous body of evidence telling us that the COVID-19 vaccines do not interfere with fertility or pregnancy.

But I heard that the vaccines cause damage to the placenta. Is that true?

No, that is not true.

This rumour began to circulate around the time the first COVID-19 vaccines were approved for use in Canada and the United States. The claim behind it focuses on syncytin-1, which is a key protein in placenta development.

The claim, and variations of it, suggested that the SARS-CoV-2 spike protein and syncytin-1 have similar structures and that training your immune system to recognize and attack the spike protein would “trick” it into attacking syncytin-1. The conclusion was that this immune response would cause damage to the placenta and put pregnancies at risk. But this is not the case.

In reality, the coronavirus spike protein and syncytin-1 have very different structures, so the claim was flawed from the start. To be extra sure, researchers have also conducted studies to test for “cross-reactivity.” This means that they ran tests to see if antibodies the immune system produces against the spike protein would react to syncytin-1. They did not find any evidence of cross-reactivity, meaning that the antibodies didn’t even notice syncytin-1, let alone attack it.

While the COVID-19 vaccines do not cause damage to the placenta, COVID-19 infection during pregnancy can cause harm. Read more below.

How can we be sure about all of this if there were no pregnant volunteers in the clinical trials?

Many studies are being conducted on everything from cross-reactivity of antibodies (as described above) to COVID-19 vaccination impacts on ovary function, implantation rates for embryos with in vitro fertilization, general fertility rates (ability to become pregnant), pregnancy duration, pregnancy loss, and maternal/newborn health outcomes.

Some of these studies have looked at tissues in a lab, some monitor health record data to spot irregularities and trends, and some larger-scale research involves recruiting volunteers for detailed follow-up (such as surveys, blood or other bio samples, etc.).

This is an intense area of study, and much of the work is being led by independent researchers at universities and hospitals—here in Canada and around the world. Thanks to the hard work completed so far, a number of studies have been published in high quality, reputable scientific journals. For longer-term studies, many researchers have also released preliminary reports and data publicly so that other experts can scrutinize and learn from the information.

So, overall, there is a growing body of scientific evidence available about COVID-19 vaccines and fertility. And what it tells us—based on the many studies to date—is that the vaccines do not affect your ability to become pregnant or carry a pregnancy to term.

But let’s talk about some of the specific details.

While it’s true that pregnant volunteers were excluded from the clinical trials for COVID-19 vaccines, some volunteers became pregnant over the course of the trials. If we look solely at the Pfizer/BioNTech (Comirnaty) and Moderna (Spikevax) vaccines, the data shows:

These numbers were small, but it was good news right from the start. If either vaccine had decreased fertility, then we would not have seen half of these pregnancies in the test groups. The data shows the chances of conceiving were about the same in the control groups and in the test groups.

The pregnancies were all monitored, and no concerns were raised. Those outcomes were in line with what was expected, as developmental and reproductive toxicity studies with rodents indicated that the vaccines had no impact on the rodents’ ability to become pregnant or carry the pregnancy, and there was no harm to the pups if the vaccine was administered during pregnancy.

Fast-forward to today, with vaccine rollouts well under way, and we still have no red flags related to the COVID-19 vaccines and human fertility (ability to become pregnant) or pregnancy.

And this is based on a whole lot of monitoring. For example:

This type of research will continue, and vaccine safety will continue to be monitored around the world, but the data to date about COVID-19 vaccines, fertility and pregnancy have not led to any reasons for concern.

But why is vaccination recommended if you are pregnant now or planning to become pregnant?

In addition to studying the vaccines and pregnancy, researchers have been looking at the impacts of COVID-19 disease on pregnancy. This has been a necessary step in determining whether vaccination should be recommended, as it provides important insight into potential risks and benefits.

When the pandemic began, it brought a lot of questions with it: What happens if someone gets sick with COVID-19 during pregnancy? What impacts could COVID-19 have on the pregnancy, and what does it mean for maternal and newborn health?

To answer these questions, the systematic collection and analysis of data became critical—and researchers in Canada and around the world were up to the challenge.

For example, Dr. Deborah Money leads the Canadian Surveillance of COVID-19 in Pregnancy project, also called CANCOVID-Preg, out of the University of British Columbia. The recent data from this national project indicates that about 7.8% of pregnant people who get sick with COVID-19 will require hospitalization because of it and 2% will be admitted to intensive care (ICU).

Those percentages may seem small, but they only tell part of the story. It’s important to compare those figures to what happens in patients of the same age who are not pregnant in order to get a sense of whether there is a higher risk for those outcomes one way or the other. And based on the current data,
you are 3 times more likely to be hospitalized if you get sick with COVID-19 during pregnancy (compared to non-pregnant peers) and 6 times more likely to end up in the ICU.

The research also shows that the risk of preterm birth is higher in pregnant patients with COVID-19. The rate of babies being born too early is 6.8% in patients who do not have COVID-19 compared to 11% in those with COVID-19.

Additional studies are also providing evidence that getting sick with COVID-19 during pregnancy can have negative impacts on the placenta. More research is needed to understand the specific mechanisms at work, but some evidence suggests that the inflammatory immune response associated with fighting the virus can lead to these abnormal changes in the placenta—so while the vaccine does not lead to placenta issues, the real virus can cause harm.

Overall, the current body of scientific evidence indicates that pregnant people have a greater risk of developing severe illness if they get sick with COVID-19 (compared to non-pregnant peers) and of experiencing pregnancy complications (compared to uninfected pregnant peers). And given the scientific evidence showing that the COVID-19 vaccines are safe to receive during pregnancy—and that the vaccines are not associated with any increased risks for pregnancy complications—experts in Canada and many other countries recommend vaccination, whether you are pregnant now or plan to become pregnant in the future because the vaccines help protect you against severe illness.

Read more about COVID-19, pregnancy, childbirth and caring for a newborn

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