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Are the COVID-19 vaccines safe during pregnancy? Experts weigh in

Bridget Balch, Staff Writer
March 4, 2021

Pregnant people were not included in initial clinical trials, but scientists point to encouraging evidence of the vaccines’ safety, especially when weighed against the high risk associated with COVID-19 in pregnancy.

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Victoria Heinrich, an MD-PhD student at the University of Pittsburgh, poses after getting her COVID-19 vaccine while 20 weeks pregnant.
Victoria Heinrich, an MD-PhD student at the University of Pittsburgh, poses after getting her COVID-19 vaccine while 20 weeks pregnant.
Courtesy: Victoria Heinrich

Julia Eicher, DO, really wanted a baby.

She and her husband had been trying to start a family and she’d lost a pregnancy, so when she became pregnant again in May 2020, she was overjoyed.

Still, with the joy came worry.

Eicher was about to start her first year of residency in family medicine at Mount Sinai Health System in New York City, where she would be treating COVID-19 patients. She knew that her pregnancy would put her in a higher risk category than her peers who were not pregnant. Eicher had heard about pregnant patients who had contracted COVID-19 and ended up in dire shape in the intensive care unit.

“It was definitely something that was really scary for me,” she says.

Through the summer and fall, Eicher lived with that anxiety as she continued to see patients.

Then in early January, she was offered a COVID-19 vaccine. She promptly rolled up her sleeve and posed for a photo with her 31-week-pregnant belly to be posted on the hospital’s Facebook page.

Eicher was shocked to see thousands of comments condemning her for putting her unborn child at risk. She had been well aware of the lack of clinical data on the safety of the COVID-19 vaccines during pregnancy, but she’d done her research and concluded that the risks of getting COVID-19 outweighed the risks of getting the vaccine. Even so, the comments made her second-guess herself.

“That was the only time I felt like maybe it wasn’t the right move,” Eicher says.

Confusing guidance and lack of data stoke fears

For many people of childbearing age, the decision about whether to get vaccinated has been clouded by mixed messages. Debunked rumors that the vaccines could cause infertility have circulated on social media, and because pregnant people were excluded from clinical trials, public health officials have been hesitant to encourage expectant parents to be vaccinated.

The World Health Organization cites the lack of data in its decision not to actively recommend the Moderna and Pfizer-BioNTech mRNA vaccines to pregnant people, but it also contends that there is no reason to believe the risks outweigh the benefits. The Centers for Disease Control and Prevention (CDC) also stops short of recommending vaccinations for pregnant people, instead saying that ongoing testing has not demonstrated any safety concerns and that pregnant people who are eligible for the vaccine may receive it.

“Not only is research with pregnant people ethically allowable according to federal guidance and general ethical considerations, also it is ethically required as a matter of justice.”

Anne Lyerly, MD
OB-GYN, professor of social medicine, and associate director of the Center for Bioethics at the University of North Carolina at Chapel Hill

Long before COVID-19, the exclusion of pregnant people from clinical trials has been common for both vaccines and medications due to ethical — and potential legal liability — concerns. Researchers fear the interventions could cause harm to an unborn baby and frequently view pregnant people as vulnerable due to the complex physiology associated with pregnancy, according to the National Institute of Health Office of Research on Women’s Health.

But excluding pregnant people from research could place them and their children at even more risk, says Anne Lyerly, MD, an OB-GYN, professor of social medicine, and associate director of the Center for Bioethics at the University of North Carolina at Chapel Hill.

“Not only is research with pregnant people ethically allowable according to federal guidance and general ethical considerations, also it is ethically required as a matter of justice,” she says.

Lyerly decided to dedicate her work in bioethics toward advancing research during pregnancy after she became frustrated over the lack of data to inform treatment for her pregnant patients.

Frequently, doctors and their pregnant patients must decide how to treat serious health issues — such as cancer, diabetes, and psychiatric disorders — without much data on the safety of medications during pregnancy or the proper dosing for the pregnant body, Lyerly wrote in a viewpoint for the AAMC in 2018.

Last month, Pfizer-BioNTech announced that it had begun a clinical trial with 4,000 healthy pregnant women to test the safety and immune response of its vaccine in them and their children. The trial will compare results from the women who are vaccinated and women who are given a placebo, and it will track the infants’ outcomes until they are six months old.

The trial will last seven to 10 months, so the final results will not be available to help many of those who are currently pregnant make their decision.

A third vaccine developed by Johnson & Johnson, which received emergency use authorization last weekend, will also include pregnant people in clinical trials at some point, according to the company’s report to the Food and Drug Administration.

Pregnancy associated with higher COVID-19 risks

CDC surveillance reports suggest that pregnant people have an increased risk of developing severe outcomes of COVID-19 — including needing intensive care unit admission, requiring invasive ventilation, and dying. The risk was especially apparent among people age 35-44, who were nearly four times as likely to need a ventilator and twice as likely to die as people who were not pregnant in the same age category, the November report said. This increased risk could be due to physiological characteristics of pregnancy that include increased heart rate and oxygen consumption, decreased lung capacity, a weakened immune system, and blood clotting, according to the report.

Another study that included 1,200 pregnant patients with COVID-19 at 33 hospitals found that those who experienced severe symptoms were at higher risk of complications during and after pregnancy, including cesarean section, high blood pressure, and premature birth.

Those who had adverse outcomes also tended to be older, have higher body mass indices, or have comorbidities such as high blood pressure or asthma, according to Torri Metz, MD, an associate professor and vice chair of research of obstetrics and gynecology at the University of Utah School of Medicine in Salt Lake City who led the study.

“This adds a bit more information for women,” Metz says. “We want to encourage [pregnant] women to do anything they can to avoid contracting the virus.”

Is the vaccine safe?

While clinical trials of the vaccines on pregnant people have only just begun, scientists say the evidence they have so far on the safety of the vaccines is promising. And claims circulating on social media that the mRNA vaccines can cause infertility are just not supported by the science, says Stephanie Langel, PhD, a postdoctoral scholar studying maternal and neonatal immunity at Duke University in North Carolina.

The claims allege that the vaccines target a protein, syncytin-1, which is vital to the formation of the placenta. In fact, the vaccines train cells to create the spike protein that SARS-CoV-2 — the virus that causes COVID-19 — uses to attach to cells. Although the protein does contain short stretches of similar nucleotides, it is not nearly enough to confuse the body’s immune response, says Langel. Many other vital proteins have similar nucelotide sequences, but the vaccines don’t attack those other proteins.

“[If they did,] we would be seeing mass rejection of the vaccines,” she explains.

Akiko Iwasaki, PhD, an immunologist at Yale School of Medicine, and her team also compared the SARS-CoV-2 spike protein with syncytin-1. They found no notable similarities. They also analyzed serum from women who had COVID-19 and found no reaction between the antibodies and the placental syncytin-1.

Since millions of people across the globe have been infected with COVID-19 and vaccinated already, doctors and scientists would likely already be seeing indications of fertility problems if there were any.

But the opposite is true, Langel says.

Several people included in the initial clinical trials became pregnant during the trials, and the CDC is also tracking thousands of vaccinated pregnant people with no red flags so far.

The mRNA vaccines were also tested in rats and did not harm their ability to reproduce, nor did they cause developmental abnormalities for the offspring.

Plus, getting vaccinated could extend protection to the baby, even after birth. Langel, who had a child last July, is studying whether she — and others — may be able to pass antibodies to their babies through breast milk and whether these antibodies can provide protection from the virus.

“A very personal decision”

The American College of Obstetricians and Gynecologists’ guidance on the vaccines state that a patient’s decision to accept or decline a vaccine should be respected. Public health officials note that, even though pregnant people are at higher risk than their nonpregnant peers, the chances of suffering a severe COVID-19 outcome are still small.

“I’ve been surprised. I’ve had patients who I would have thought would jump at the vaccine and they have been hesitant and others that I thought would be hesitant and they were happy to get vaccinated,” says Maryam Siddiqui, MD, an associate professor of obstetrics and gynecology at the University of Chicago Pritzker School of Medicine. “It’s a very personal decision.”

Siddiqui explains that she advises her patients to consider their personal level of risk, such as the likelihood of being exposed and underlying conditions that could make COVID-19 worse. She recommends using an online tool — like the one created by FOAMcast, an emergency medicine podcast that provides clinical resources — to help assess their situation and decide what’s best for them.

“I would do whatever it took to reduce the risk during the pregnancy.”

Marlise Pierre-Wright
Third-year medical student at Northwestern University Feinberg School of Medicine in Chicago, Illinois

Marlise Pierre-Wright, a third-year medical student at Northwestern University Feinberg School of Medicine in Chicago, wishes she had the opportunity to get vaccinated while she was pregnant during the first months of the pandemic.

Marlise Pierre-Wright, a third-year medical student at Northwestern University Feinberg School of Medicine in Chicago, holds her daughter, Camille.
Marlise Pierre-Wright, a third-year medical student at Northwestern University Feinberg School of Medicine in Chicago, holds her daughter, Camille.
Courtesy: Marlise Pierre-Wright

“Since I’m a Black woman, it’s already a risk to be pregnant,” Pierre-Wright says. “I would do whatever it took to reduce the risk during the pregnancy.”

Pierre-Wright didn’t feel comfortable going back into a clinical environment where she could risk exposing herself and her unborn baby. Fortunately, she was able to continue her coursework virtually until her daughter, Camille, was born in July and she completed her maternity leave.

After that, she had to make the decision whether to go back into the hospital and risk bringing the virus home to her newborn. Since the evidence showed babies were not very susceptible to COVID-19, she went back to work. Then, when her turn came, she got vaccinated.

“It makes you feel like you have a superpower,” she says.

Victoria Heinrich, an MD-PhD student at the University of Pittsburgh, might have had the opportunity to be included in Moderna’s clinical trial last year when her husband was recruited, but because she had just found out she was pregnant with her second child, she wasn’t eligible.

Julia Eicher, DO, a first-year resident at Mount Sinai Health System in New York City, holds her newborn son, Nico.
Julia Eicher, DO, a first-year resident at Mount Sinai Health System in New York City, holds her newborn son, Nico.
Courtesy: Julia Eicher

Knowing the risks of catching COVID-19, Heinrich would sometimes take the freight elevator at work to try and avoid people crowding in such a small space. She would think about her 2-year-old daughter and worry about what would happen to her if she caught the virus and suffered one of the worse outcomes. So, when she was offered a vaccine in January, 20 weeks into her pregnancy, she took it. Two days after her first dose, she had an ultrasound.

“The baby was perfectly fine,” Heinrich says. “He was bouncing around and kicking.”

And for Eicher, the resident who endured negative comments on Facebook, the vaccination also turned out to be the right decision.

“It was totally worth it,” she says. “I felt so much safer.”

On Feb. 7, she gave birth to a healthy 8-pound, 3-ounce son, Nico.

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