COVID-19 vaccination and pregnancy
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:
- A total of 36 volunteers became pregnant (23 in the Pfizer/BioNTech groups and 13 in the Moderna groups).
- About half of those pregnancies occurred in the control groups (those who did not receive the vaccine) and the other half occurred in the test groups (those who did receive the vaccine):
- 12 pregnancies in the control group for Pfizer/BioNTech, 11 pregnancies in the test group; and
- 7 pregnancies in the control group for Moderna, 6 pregnancies in the test group.
- No pregnancy loss (miscarriage) was reported in the test groups for either vaccine.
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:
- Early data is available from the Canadian COVID-19 Vaccine Registry for Pregnant and Lactating Individuals—also known as COVERED. This is a national survey on COVID-19 vaccines in pregnancy that is being led by Dr. Deborah Money from the University of British Columbia. Analysis is ongoing for this study, but the data to date from over 5,000 volunteers do not raise any safety concerns. In fact, it shows no adverse events related to receiving the vaccine and no increase in pregnancy complications.
- In the United States, a small study focused on in vitro fertilization frozen embryo transfer found that the immune response from vaccination “does not prevent embryo implantation or early pregnancy development.” This led the researchers to conclude that “neither previous illness with COVID-19 nor antibodies produced from vaccination to COVID-19 will cause sterility.”
- Additional Canadian research includes several independent studies supported through the COVID-19 Immunity Task Force to examine the impact of SARS-CoV-2 infection and COVID-19 vaccination on pregnancy and newborns. One such study, led by Dr. Deshayne Fell from the University of Ottawa and Children’s Hospital of Eastern Ontario Research Institute, examined specific pregnancy and birth outcomes. The team found that COVID-19 vaccination during pregnancy [ PDF (599 KB) - external link ] did not lead to any increased risks of adverse outcomes at the time of delivery.
- A small study in Israel looked specifically at ovarian follicular function and found that “neither infection or the BNT162b2 mRNA vaccine nor the immune response to them resulted in any measurable detrimental effect on the function of the ovarian follicle.” In short, the study found that vaccination did not have a negative impact on the ovaries (and neither did COVID-19 illness).
- In January 2022, the European Medicines Agency’s COVID-19 task force released their findings from studies involving approximately 65,000 pregnancies at various stages. “The review did not find any sign of an increased risk of pregnancy complications, miscarriages, preterm births or adverse effects in the unborn babies following mRNA COVID-19 vaccination. Despite some limitations in the data, the results appear consistent across studies looking at these outcomes.”
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
Related reading
- Vaccination and pregnancy: COVID-19
- Society of Obstetricians and Gynaecologists of Canada (SOGC) Statement on COVID-19 Vaccination in Pregnancy [ PDF (266 KB) - external link ]
- The Incidence, Severity, and Management of COVID-19 in Critically Ill Pregnant Individuals
- COVID-19 Vaccination During Pregnancy in Ontario
- The impact of COVID-19 disease & vaccination on pregnancy and newborns
- Date modified: