COVID-19 mRNA Vaccine (Moderna/Spikevax® and Pfizer/Comirnaty®)

Last Update: 11 Mar 2025

Medication

Table of content

1. What is it? 2. What are the risks according to research? 3. Breastfeeding/ chestfeeding 4. What about fathers and sperm donors? 5. Key points

Welcome to our fact sheet on COVID-19 mRNA vaccines during pregnancy and breastfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (data from August 2024).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

Watch our video to lear more about vaccines during pregnancy!

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1. What is it?

What is COVID-19?

COVID-19 (short for Coronavirus Disease 2019) is an illness caused by a virus called SARS-CoV-2. The virus easily spreads from person to person through respiratory droplets that come from our mouths and noses when we breathe, talk, cough, or sneeze. For more information on COVID-19, please see our fact sheet here.

What is a COVID-19 mRNA vaccine?

A COVID-19 messenger RNA (mRNA) vaccine helps protect against the virus that causes COVID-19. It is often simply called a “COVID vaccine.” Brand names of COVID-19 mRNA vaccines in the United States and Canada are Moderna/Spikevax® and Pfizer/Comirnaty®. COVID-19 mRNA vaccines do not contain live virus that could cause COVID-19. COVID-19 vaccines are not 100% effective at preventing COVID-19, but can greatly lower the chance of getting very sick from the virus.

For more information on another kind of COVID-19 vaccine, please consult our fact sheet in collaboration with MotherToBaby here.

Are COVID-19 mRNA vaccines recommended for pregnant individuals?

The Centers for Disease Control and Prevention (CDC) recommend that pregnant individuals, individuals planning a pregnancy, or individuals who could become pregnant in the future stay up to date with COVID-19 vaccines. A COVID-19 mRNA vaccine can be given at any time in pregnancy. Talk to your healthcare provider or visit the Health Canada website to learn how to stay up to date with COVID-19 vaccines: https://www.canada.ca/en/public-health/services/diseases/coronavirus-disease-covid-19/vaccines.html.

Having a COVID-19 infection while pregnant increases the chance of severe illness and pregnancy complications. Studies have shown that people who are up to date with COVID-19 vaccines in pregnancy are less likely to get very sick or have pregnancy complications from a COVID-19 infection than people who are not up to date.

2. What does research say about the risks?

Can getting a COVID-19 mRNA vaccine make it harder for me to get pregnant or affect fertility treatments?

Some people have reported changes in their menstrual cycle (period) after getting a COVID-19 mRNA vaccine, such as having a slightly longer or heavier period or starting their next period sooner than expected. Studies have found that if these changes happen, they are temporary and do not affect the individual’s fertility.

Studies of individuals undergoing in-vitro fertilization (IVF) have found no effect of COVID-19 mRNA vaccines on the function of the ovaries (the organ that releases the egg), number of oocytes (immature eggs), hormone levels, or success rates of embryo implantation. Most studies have not found differences in pregnancy rates between recently vaccinated and unvaccinated individuals undergoing fertility treatments. There is currently no recommendation to postpone fertility treatment after getting a COVID-19 mRNA vaccine or to avoid getting the vaccine during or after treatment.

I just got a COVID-19 mRNA vaccine. How long do I need to wait before I get pregnant?

There is no recommendation to wait before trying to get pregnant after getting a COVID-19 mRNA vaccine.

Does getting a COVID-19 mRNA vaccine increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not found a higher chance of miscarriage after getting a COVID-19 mRNA vaccine anytime in pregnancy.

Does getting a COVID-19 mRNA vaccine increase the chance of birth defects?

Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at published data to try to understand if an exposure, like a COVID-19 mRNA vaccine, might increase the chance of birth defects in a pregnancy. Studies have not found a higher chance of birth defects after getting a COVID-19 mRNA vaccine anytime in pregnancy.

Fever is a possible side effect of getting a COVID-19 mRNA vaccine. A high fever in the first trimester can increase the chance of certain birth defects. Acetaminophen is usually recommended to reduce fever during pregnancy. For more information about fever and pregnancy, see the MotherToBaby fact sheet about fever/hyperthermia at https://mothertobaby.org/fact-sheets/hyperthermia-pregnancy/.

Does getting a COVID-19 mRNA vaccine in pregnancy increase the chance of other pregnancy-related problems?

Studies have not found an increased chance of pregnancy-related problems or newborn complications such as stillbirth, preterm delivery (birth before week 37), babies born smaller than expected, low Apgar scores, admission to a neonatal intensive care unit (NICU), or neonatal death when a COVID-19 mRNA vaccine is given anytime during pregnancy.

Does getting a COVID-19 mRNA vaccine in pregnancy affect future behavior or learning for the child?

It will take time to follow the children of individuals who were vaccinated in pregnancy in order to be able to answer this question. However, based on what is known about how mRNA vaccines work in the body, getting a COVID-19 mRNA vaccine is not expected to cause long-term problems for the child.

Does getting a COVID-19 mRNA vaccine during pregnancy protect the baby from COVID-19 after delivery?

Getting a COVID-19 mRNA vaccine during pregnancy can pass antibodies to the fetus. After delivery, the baby might have some protection against COVID-19 and might be less likely to be hospitalized due to a COVID-19 infection in the following months.

3. Breastfeeding and COVID-19 mRNA vaccines

Small studies have found that mRNA from COVID-19 mRNA vaccines is unlikely to enter the breast milk. If any small amounts of vaccine ingredients did enter the breast milk, they would most likely be destroyed in the baby’s stomach. Studies have not reported serious adverse reactions to COVID-19 mRNA vaccines in breastfeeding individuals or their infants. Less than 10% of individuals reported changes in milk supply (more or less milk) after getting a COVID-19 mRNA vaccine, but their supply returned to normal within a day or two.

Organizations including the Academy of Breastfeeding Medicine (ABM) and the American Academy of Pediatrics (AAP) agree that breastfeeding individuals can receive a COVID-19 mRNA vaccine. There is no recommendation to postpone breastfeeding or discard breast milk after getting a COVID-19 mRNA vaccine.

Antibodies against the virus that causes COVID-19 have been found in the breast milk of individuals who have received an mRNA vaccine. More research is needed to know how these antibodies might protect a breastfeeding child against the virus. Talk to your healthcare provider about all of your breastfeeding questions.

4. What about fathers and sperm donors?

If a male gets a COVID-19 mRNA vaccine, could it affect his fertility or increase the chance of birth defects?

Studies have found no differences in sperm production before and after getting a COVID-19 mRNA vaccine. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures here.

Key points

mRNA COVID-19 vaccines (Moderna/Spikevax® and Pfizer/Comirnaty®) help protect against the COVID-19 virus.
They are recommended at any stage of pregnancy to reduce the risk of complications and severe illness.
Studies have not shown an increased risk of miscarriage, birth defects, or other pregnancy-related complications.
Breastfeeding individuals can receive an mRNA vaccine. No serious adverse reactions have been found. Protective antibodies may be passed through breast milk.
Consult your healthcare professional if you have questions specific to your situation.

References

Please click here for references.

Disclaimer

HEALTHY PREGNANCY HUB provides a source of information validated by health professionals; however, this information is provided for informational purposes only and should not replace professional advice. Medical standards and practices evolve as new data becomes available, so it is imperative to consult your doctor or a qualified health professional for any questions or concerns regarding your health without delay or omission. It is the responsibility of your treating physician or any other health professional, based on their independent experience and knowledge of the patient, to determine the best way to evaluate and treat you.

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While consulting symptoms or other medical information on our platform may guide your discussions with your healthcare professional, this information should not be used to make a medical diagnosis or determine treatment. Before making changes to your supplement or medication regimen, please discuss with your medical team or contact 811 (Canada) to ensure the relevance of these changes to your individual situation.

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