Healthy Pregnancy

What Doctors Want You To Know About the COVID-19 Vaccine for Pregnant People

Erin Bunch

Photo: Getty Images / bogdankosanovic
When you're pregnant, every decision you make about your body takes on new weight—down to what night creams you use and how much coffee to drink. So, trying to figure out whether to take a brand new vaccine—or risk getting COVID-19—is no small task for expectant parents, especially in the disinformation age. There does seem to be one consensus opinion among experts, however: COVID-19 vaccines should be available to pregnant women, who must then weigh the option individually (along with their health care providers) in the absence of black-and-white guidance.

This conclusion puts expectant mothers right back where they began: likely agonizing over this difficult choice. Below, doctors and epidemiologists answer five common questions regarding the safety of the COVID vaccine for pregnant women.

1. Have the vaccines been tested on pregnant women?

None of the vaccines to date—and this includes the Pfizer, Moderna, and Johnson & Johnson vaccines—have been formally tested on pregnant women to confirm their safety. "None of the trials included women who were actively trying to conceive or already pregnant/breastfeeding," says Lucky Sekhon, MD, fertility specialist and board-certified OB/GYN. "[Excluding pregnant/breastfeeding women] is standard practice for any clinical trial studying a new therapy [or] drug." (This is typically because researchers don't know how a drug could potentially impact the health or development of a fetus.)

Instead, researchers often rely on animal studies for safety guidance. Dr. Sekhon notes that the Moderna vaccine was tested on rats who were mated, and no difference was found in their ability to get pregnant, in fetal development, or in the health of their offspring when compared to rats who did not get the vaccine. Animal testing using the Pfizer vaccine also did not indicate harmful effects with respect to pregnancy, fetal development, or post-natal development.

Also worth noting: Around two dozen women inadvertently conceived during the Pfizer vaccine trial, and Dr. Sekhon says they are being monitored. A significant number of pregnant women have also opted to get the vaccine since it's become available in the U.S. "So far, there are no red flags or concerning data coming out of the 10,000 pregnant women who have received the vaccine thus far," says Dr. Sekhon. All in all, fairly promising (although not totally conclusive) signs of the safety of these vaccines for pregnant women.

2. What are the potential risks of getting the vaccine for pregnant people?

In the absence of results from clinical trials, experts can ultimately only speculate as to the risks of vaccination, says Dr. Sekhon. She notes that there may be some concern around vaccine side effects, such as fever, in the first trimester of pregnancy. "Some studies have linked first trimester fevers that go untreated with birth defects impacting the spinal cord [aka neural tube defects]," she says. "[However], this is not a definitive link."

Generally, vaccines themselves are typically fairly safe for pregnant people; women have been and continue to be safely vaccinated during pregnancy for other illnesses, including tetanus, diphtheria, and whooping cough. "We have history of other vaccines in pregnancy that are given safely so we're looking at that as sort of kind of reassurance, if you will, to say we are used to vaccinating pregnant women, as opposed to doing some completely novel treatment that nobody's ever tried before," says Laila Al-Marayati, MD, division chief of obstetrics and gynecology, Keck Medicine of USC.

Pregnant people are even counseled to get flu shots; however, the ones they receive specifically do not contain live viruses because pregnant women are advised against receiving vaccines that do (e.g. the measles, mumps, and rubella vaccine) due to the theoretical risks of passing that virus to the fetus.

Fortunately, the vaccines currently available to prevent COVID-19 do not contain live virus. The Pfizer and Moderna vaccines use messenger RNA (mRNA) technology, which basically provides our cells with instructions to build a protein found in the SARS-CoV-2 virus so that the immune system can create the antibodies needed to protect against COVID-19 infections. This mRNA degrades, or disappears, quickly once the protein is developed, leaving the cells as they were. "Since neither vaccine contains live virus and mRNA does not integrate into the human DNA genome, there is no theoretical reason to assume there is a risk to pregnant women or their fetuses," says Timothy Brewer, MD, professor of medicine and epidemiology at UCLA. "However, there are no data."

3. Since some of the vaccines utilize different technologies, is one type of vaccine potentially safer than another?

New vaccines utilizing different, non-mRNA technologies are forthcoming. Johnson & Johnson, for example, recently completed its Phase 3 trials on its COVID-19 vaccine, which uses different technology to the same effect. The new vaccine (which is being now considered by the FDA for emergency use authorization) sends the genetic code for the SARS-CoV-2 protein into cells by injecting the body with an adenovirus (a common virus, such as that which causes a cold) that's been modified so that it can enter cells but not alter them or replicate. While this vaccine has not been tested on pregnant women either, other vaccines using the same adenovirus technology have been given to women who got pregnant during those trials. Johnson & Johnson has reportedly said there is no concerning evidence of ill effects as a result, so theoretically the risks would be similar with this new COVID-19 vaccine, too. The AstraZeneca and Novavax vaccines (not yet approved for use in the U.S.) also utilize a weakened adenovirus that's been modified to look like SARS-CoV-2.

Want to learn more about how vaccines work? A biochemist breaks it down for Well+Good:

As for whether or not adenovirus versions of the vaccine are potentially safer for pregnant women than the Moderna or Pfizer vaccines, or vice versa, Dr. Al-Marayati says it's probably too soon to tell. Dr. Sekhon is more bullish in her response, however, which is a hard "no" with respect to whether there's any safety difference between the two. "All of the major vaccines use either mRNA or inactivated virus delivered by the common cold virus or an inactivated protein subunit of the COVID-19 virus," she says. "None of the vaccines are live virus vaccines, which are contraindicated in pregnancy and considered a danger."

4. How are expert organizations and OB/GYNs advising pregnant women regarding the vaccine at present?

While this is a tricky choice for any woman to be faced with making, there is professional consensus around the idea that the vaccine should be available to women who want to take it. "Because of the lack of evidence for concern that the vaccine could hurt a fetus, The American College of Obstetricians and Gynecologists (ACOG), the Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and other major health organizations have all been unified in their recommendation that the vaccine should be offered to pregnant women and those trying to conceive," says Dr. Sekhon. The Society for Maternal Fetal Medicine (SMFM) also strongly recommends that pregnant women have access to COVID-19 vaccines.

From there, experts say it's a personal decision each individual has to make for themselves. "I advise [patients] to weigh their personal risks of COVID-19—increased risk of severe disease, hospitalization, need for mechanical ventilation, and death as a pregnant woman who catches COVID-19, and the increased risk of preterm delivery prior to 37 weeks—which may also include their risk/threat level...against the risks of the unknown," says Dr. Sekhon. "My personal viewpoint, having reviewed the data at hand and the indirect evidence versus what we know about COVID-19 in pregnancy, is that all pregnant women should strongly consider taking the vaccine."

"My personal viewpoint, having reviewed the data at hand and the indirect evidence versus what we know about COVID-19 in pregnancy, is that all pregnant women should strongly consider taking the vaccine." —Lucky Sekhon, MD, OB/GYN

Dr. Al-Marayati is in the same boat. "Our position, at least in my practice, is that we believe any potential risks are outweighed by the benefits of not getting COVID. So we recommend vaccines for pregnant patients." That said, she recognizes that the risk-benefit ratio of vaccination varies per patient, however. The majority of her pregnant patients getting the vaccine are health-care workers, she says, noting that those with a lower risk of exposure may choose to opt out until there's more hard data. Those with underlying conditions like lung disease, obesity, and immunological problems are also more strongly encouraged to get the shot than those who don't have those conditions.

But COVID-19 can be dangerous, period, adds Dr. Al-Marayati. Research shows that pregnant women with symptomatic COVID-19 are more likely to experience intensive care unit admission, invasive ventilation, and death than non-pregnant women with symptomatic COVID-19. Even if an infection is not that bad, she'd prefer that her patients avoid it because pregnancy can complicate treatment, and vice versa.

The ACOG does recommend that women treat any fevers that may arise from the vaccine, says Dr. Sekhon, and that they refrain from taking any other vaccines for at least 14 days, with one exception: the RhoGAM shot (which protects you and your fetus from complications arising from blood type incompatibility). She also notes that if you're worried about the "theoretical risks" of getting a fever in your first trimester, you may want to wait until you're further along in your pregnancy to get the vaccine.

5. If you're planning a pregnancy this year, is it best to get a vaccine first? And can the vaccines affect fertility?

Those who are planning to get pregnant this year find themselves faced with a conundrum, especially given the uncertainty of when vaccines will become available to child-bearing age brackets. Should they postpone trying to conceive until after they've been vaccinated, or just continue on their planned schedule and deal with the vaccine once it arrives, at whatever stage in their pregnancy journey that may be?

According to Dr. Sekhon, there is no evidence to suggest that it's better to get vaccinated before pregnancy than during. "I would not factor this into planning," she says. And despite rumors to the contrary, there is no evidence or reason to believe that COVID-19 vaccines will affect your fertility if you do wait until after vaccination to attempt conception. "The vaccine cannot impact your fertility or ability to conceive," says Dr. Sekhon.

She says that the specific theory around infertility and the vaccine—which is that the proteins created/injected by COVID-19 vaccines are similar to those found in a healthy placenta, and therefore developing antibodies to attack them could cause fertility issues—has been debunked. "The theorized cross-reactivity between the antibodies directed against the coronavirus spike protein and the placental protein, syncytin-1, has been disproven," she says. "We also see similar levels of similarity in the genetic sequence of the spike protein and proteins that make up collagen and hemoglobin, which are ubiquitous in our bodies. Clearly, there is no cross-reactivity between the antibodies from the vaccine and these proteins, given the favorable side effect profile and safety demonstrated in large trials." In other words, if the vaccine were causing attacks on proteins in the body similar to the COVID-19 proteins it creates/injects, we would already have data, unrelated to pregnancy, showing that to be the case.

This conclusion is fairly definitive, but much around this vaccine and pregnancy is not. "We can't answer the question that everybody wants to know, which is, 'It safe for pregnant women, is it unsafe for pregnant women, should we or shouldn't we get the shot?," says Dr. Al-Marayati. In the absence of absolutes, your best bet if pregnant or trying to conceive, then, is to work with your health-care providers to make a decision considering the above information alongside your own health data and exposure risk. 

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