Answering Your Questions on COVID-19 Vaccines and Pregnancy

I spent time during prenatal visits earlier in the pandemic discussing COVID-19 concerns and prevention strategies, but now I find myself fielding the same few questions about the vaccine from patients and colleagues alike.

Q: Would you recommend the COVID-19 vaccines to pregnant patients?

A: The short answer is a resounding yes, and I share that several organizations, including the AAFP, the American College of Obstetricians and Gynecologists, the Society for Maternal-Fetal Medicine and the CDC, agree that the COVID-19 vaccines should not be withheld from pregnant patients. I also explain that pregnancy itself puts them at higher risk for severe complications of COVID-19, and in some cases preterm deliveries if necessary to manage maternal COVID-19 complications.

In January, the World Health Organization issued interim guidance stating, among other things, that pregnancy itself increases the risk of severe COVID-19 compared with women of childbearing age who aren’t pregnant. The WHO also stated that it did not have any specific reason to believe there would be specific risks that would outweigh the benefits of vaccination for pregnant women, and as such believes that pregnant women who are at high risk of exposure to SARS-CoV-2 or who have comorbidities that add to their risk of severe disease may be vaccinated in consultation with their health care professional. The WHO has also stated that it will continue to update its guidance as more information becomes available.

However, in answering this question I take some time to review how the COVID-19 vaccines work, in order to set the stage for some of the questions that commonly follow. I explain that neither the mRNA vaccine nor the Janssen adenovirus vaccine contain the virus that causes COVID-19. The Pfizer-BioNTech and Moderna vaccines carry mRNA that is a recipe for the spike protein of the SARS-CoV-2 virus. The body already has the ingredients that it needs to make the spike protein, and once it does, the recipe is not needed anymore, so the mRNA degrades. This degradation happens quickly, so mRNA cannot reach the fetus or the placenta, and it does not enter the cell nucleus, so it cannot alter DNA. The Janssen/Johnson & Johnson vaccine uses DNA, which does enter the nucleus, but it does not alter the host genome in any way.

The spike protein is what allows the virus to enter our cells and is recognized as foreign, so the immune system takes over to destroy it and produce antibodies for use later if you were to be exposed to SARS-CoV-2. Antibodies are also produced after natural infection with COVID-19, and there has been no evidence to suggest an association between previous COVID-19 infection and an increase in pregnancy loss.

Q: What do we know about the safety of the mRNA vaccines in pregnant patients?

A: Pregnant and nursing patients were excluded from the vaccine trials, but patients did get pregnant during the trials, and there have been no complications reported. Moderna has released animal studies that showed pregnant, vaccinated rats had no adverse effects on female reproduction, fetal development or postnatal development.

The CDC has been actively monitoring patients who are pregnant or became pregnant for any adverse events and had over 2,700 patients enrolled in the v-safe COVID-19 Vaccine Pregnancy Registry as of March 8. As of March 1, there have been no reported increases in any pregnancy complications, including spontaneous abortion, intrauterine fetal demise, hypertensive disease of pregnancy, intrauterine growth restriction, preterm birth, congenital anomalies or neonatal death.

This is also a good time to review theoretical risks of the vaccine and known risks of COVID-19 infection. Based on the vaccine ingredients and the way the vaccine works, there is no reason to believe that it would be a threat to pregnancy. There have been some concerns circulating about an effect on the placenta causing stillbirth because the placenta also contains spike proteins. These spike proteins are in the same family as SARS-CoV-2 spike proteins, but they are not similar enough to confuse the immune system.

However, pregnant patients who contract COVID-19 are at an increased risk for ICU admission, mechanical ventilation and death. In response to this information, I often hear that patients consider themselves in a low-risk group because they are young and healthy. I use this time to remind them that everyone’s risk of contracting COVID-19 is increased when community spread is so prevalent, and that although COVID-19 may have an unpredictable disease course it is definitively more severe in pregnancy. Often this leads to a review of current activities — and activities of others in the household — that could put the patient at increased risk of exposure, and ways to mitigate them.

Q: Do the COVID-19 vaccines cause infertility?

A: There is no scientific evidence or biological mechanism to support a claim that they would. Concerns of infertility have been used to baselessly discredit multiple vaccines in the past, as well.

Specifically, this claim in relation to SARS-CoV-2 seems to relate back to the concern with spike proteins on the placenta. However, as mentioned above, the shared amino acid sequence is too short for the immune system to confuse the virus and the placenta. There has also been no increase in early pregnancy loss associated with COVID-19 infection.

Q: Can I get an mRNA vaccine if I am breastfeeding?

A: Yes, vaccination is not contraindicated for nursing patients. The biological mechanism of the vaccine leaves no plausible way for it to negatively affect a nursing child, so patients do not need to be advised to dispose of breast milk for any amount of time after vaccination. Some studies of COVID-19-positive patients have shown evidence that antibodies may be passed to the nursing child, but this has not yet been established for vaccination. However, evidence from other vaccines for respiratory diseases suggests that infant protection is likely, and in general, antibody protection is a known benefit of breastfeeding. As such, the AAFP’s policy does consider breastfeeding or delivery of expressed milk to be a reasonable choice in parents exposed to or infected with COVID-19, with the caveat that the parent should wear a mask and use appropriate hand hygiene.

There are also early data showing the presence of antibodies against SARS-CoV-2 in breast milk and umbilical cord blood from patients who were vaccinated while pregnant. The study looked at 131 patients and included pregnant, lactating and nonpregnant individuals who received either of the mRNA vaccines. Antibody levels were measured in breast milk and umbilical cord blood after delivery. While this study is small and still undergoing peer review, there may be some additional protection conferred to the baby by the vaccine.

Q: What about the Janssen (Johnson & Johnson) vaccine?

A: Again, pregnant and breastfeeding patients were not included in their trials but ACOG has already released a statement in support of its use during pregnancy and breastfeeding, stating there was no reason to believe that there would be a detrimental effect on pregnancy or breastfeeding. It should be noted that this is an adenovirus vector vaccine, so it has a slightly different mechanism of action. While it still instructs the body to make antibodies to spike proteins, those instructions are inserted into a carrier/vector for transport. A weakened adenovirus is used as the vector, but like the mRNA vaccines, they also cannot cause illness. The CDC will also be monitoring patients through the pregnancy registry.

Q: Where can I find out more?

A: The AAFP has several resources to help answer patient questions, including FAQs and short videos. The CDC continues to update its clinical considerations for the vaccines as new information becomes available.

Danielle Carter, M.D., is the new physician member of the AAFP Board of Directors.