Vaccine and pregnancy/breastfeeding…

A really tough decision. Data is limited and theoretical risk must be weighed against the established benefits. This is what we have so far…

-Individuals who got pregnant during vaccine trials had no complications from the vaccine

-Pregnant, vaccinated rats did not have any adverse effects on female reproduction, fetal/embryonal development, or postnatal developmental.

-The vaccine mRNA will not reach the baby; it degrades too quickly

-The vaccine is not “live” or “dead” or anything in between, so you won’t get infected with COVID19

-Antibodies do not attack the placenta

-There is no plausible way how the vaccine would cause harm to a breastfed baby

-Pregnant individuals are at higher risk for COVID19 complications

-CDC, FDA, ACOG, and ABM all recommend vaccination for pregnant and breastfeeding individuals in particular

Long version:

Pregnant and breastfeeding patients were deliberately excluded in the first round of COVID19 vaccine clinical trials. This is normal practice (however lately it’s been strongly debated that we should include pregnant individuals as they have been dubbed “last therapeutic orphans.” The history of this topic is fascinating.) With that said, a number of individuals in these trials did get pregnant after they were enrolled in the study: 23 in the Pfizer trial and 13 in Moderna. None had complications from the vaccine.

Moderna also published their DART results. This is an animal study done before human trials begin. This is also normal practice (not just done for COVID19). Moderna injected pregnant rats with the vaccine. Rats did not have any adverse effects on female reproduction, fetal/embryonal development, or postnatal developmental. Pfizer is still working on their study and will publish soon.

The fundamental principles of how mRNA vaccines work are important to understand:

-These vaccines do not enter the nucleus and do not alter human DNA in vaccine recipients. As a result, mRNA vaccines cannot cause any genetic changes to mom or the baby

-mRNA is degraded quickly once it sends this message to your immune system. It won’t have enough time to get to the baby even if it wanted to.

-There is no live or weakened virus in the vaccine, so you cannot become infected from the vaccination itself. Vaccines that do include live or weakened virus (like MMR) are not given during pregnancy.

-Antibodies do not attack the placenta (regardless of the misinformation circulating the internet. check out my previous post about this)

In terms of breastfeeding, there is no plausible biological mechanism for how the vaccine would cause harm to a breastfed baby. We’ve seen small studies that COVID19 positive patients DID pass antibodies to their breastfed child. Antibody protection is one of the big benefits of breastfed milk. While we do not yet have data specific to maternal vaccination, information from other respiratory disease vaccinations suggests newborn protection is likely.

Although the absolute risk for severe COVID-19 is low, symptomatic pregnant patients with COVID-19 are at increased risk of ICU admission, need for mechanical ventilation and ventilatory support, and death. This is why pregnant individuals are being offered the vaccine in the first rounds of vaccinations.

With all of this in mind, the CDC and FDA have recommended vaccination for pregnant and breastfeeding individuals. Also (and I think more importantly):

  • American College of Obstetricians and Gynecologists (ACOG): “vaccines should not be withheld from pregnant or lactating individuals who otherwise meet criteria for vaccination.”

  • Academy of Breastfeeding Medicine does not recommend stopping breastfeeding for people who get the COVID-19 vaccine.

Have a discussion with your provider. If they don’t want to have a discussion, find another provider. Here are topics to discuss:

  1. Level of COVID-19 spread in your community;

  2. Whether you have any medical conditions that elevate your risk of COVID-19 complications;

  3. Your comfort level in taking the vaccine.

This is your decision. As a scientist (and mom), all I can do is provide you with the current state of evidence. I hope this helps. And congratulations on your baby!

Love, YLE

Previous post on fertility and vaccine:

Data Sources:

Pfizer report:

Moderna report:


UK vs US recommendations:

Antibodies in human milk:

Covid risks to pregnant individuals: ; ; ; ; ;