Seven Things to Know About Covid-19 and Pregnancy

From the effect of vaccines on a baby’s immunity to whether Covid-19 can cause stillbirths, experts weigh in with helpful information and advice

Pregnant Woman Receiving Covid Vaccine
A woman who is six months pregnant receives a Covid booster shot in Los Angeles. The CDC advises pregnant women to get vaccinated. Gary Coronado / Los Angeles Times via Getty Images

Since the start of the pandemic, scientists have confirmed that individuals with preexisting conditions like lung or heart disease are at increased risk for severe illness or death from Covid-19. Over time, researchers have found that those preexisting conditions aren’t just illnesses or disorders, but also pregnancy. Pregnant women with Covid-19 were more likely to be admitted to the ICU and die than their non-pregnant counterparts according to data from the Centers for Disease Control and Prevention (CDC) from January to October 2020, before vaccines were authorized. The number of pregnant patients who have received the vaccine is increasing, though vaccine uptake is still slower among pregnant individuals than the general population. During the week of February 5, 2022, about 65 percent of pregnant patients in the U.S. were fully vaccinated against Covid-19 compared to about 75 percent of the general population over the age of 18, despite the increasing data on the vaccines’ safety and efficacy in pregnancy.

Pregnant patients are rarely included in clinical trials for new drugs and treatments, in an effort to minimize the risk to them and their babies. Unfortunately, that precedent kept them excluded from early trials for Covid-19 vaccines, meaning that once the vaccines were authorized for emergency use, regulatory agencies provided little guidance. The CDC simply recommended that pregnant women discuss the benefits and risks of vaccination with their individual health care providers.

Now, however, scientists have collected substantial evidence of the risks, to both parent and baby, of Covid-19 infection and vaccination and the CDC recommends—as of this past August— that all individuals who are pregnant, lactating or planning to become pregnant get vaccinated against Covid-19. “All the data continues to reinforce the benefit of getting vaccinated in pregnancy and I really just can't underscore that enough,” says Malavika Prabhu, a physician who specializes in caring for women and fetuses in high-risk pregnancies at Weill Cornell Medicine in New York City.

Just this week the CDC announced they had data showing that when pregnant individuals were vaccinated their babies were less likely to be hospitalized with Covid-19 in the first six months of their lives. The news is the latest update of many to our understanding of how the disease affects expectant individuals and their babies.

To help you make sense of the changing recommendations and latest research, Smithsonian reached out to experts to answer some key questions.

Does pregnancy affect a person’s ability to fight off infections?

It’s obvious that bodies change during pregnancy, what might be less obvious is that immune systems change as well. “Our immune systems are altered a little bit during pregnancy to help support the goals and development of the placenta and the fetus,” says Katherine Campbell, the medical director of the Yale-New Haven Hospital Labor & Birth, Maternal Special Care & Postpartum Units. “And some of that altered immunity is thought to also contribute to women's or persons' increased risk of having more severe infections during pregnancy.”

An example of a change in pregnancy that can exacerbate Covid-19 is swelling. Feet aren’t the only part of the body prone to swelling during pregnancy, Campbell explains. Pregnant individuals can experience swelling throughout their bodies, and even in their airways, which can exacerbate respiratory issues. At the same time, pregnant patients need to consume more oxygen to help support the fetus. That means that if they start having trouble breathing, pregnant individuals might experience low oxygen saturation sooner than a non-pregnant adult. “And usually, they can tolerate that well, but that can be dangerous for the fetus,” says Campbell. If a fetus doesn’t get enough oxygen, it can suffer birth defects or even stillbirth. Plus, swollen airways can make it difficult for a doctor to intubate a pregnant patient if it becomes necessary.

What do we know about how Covid-19 impacts pregnancy?

Experts emphasize that most pregnant individuals who get Covid-19 do not have severe outcomes, but the risk of requiring hospitalization and death is dramatically higher for pregnant patients with Covid-19 than pregnant patients without. Pregnant patients with Covid were about five times more likely (5.2 percent compared to 0.9 percent) to visit the intensive care unit (ICU) than pregnant patients without Covid, and about 15 times more likely to die in the hospital (0.1 percent versus less than 0.01 percent.) The study did not explore whether the patients were vaccinated.

One positive observation is that pregnant individuals are no more likely than the average person to actually contract the disease. “It doesn’t look like pregnant women are more likely to get Covid-19 versus a non-pregnant person,” says Prabhu. “But if they get Covid, they are more likely to be sick.”

An NIH study published in February 2022 showed that individuals who had Covid-19 during pregnancy or shortly after were more likely to experience serious complications associated with pregnancy such as hypertensive disorders, postpartum hemorrhage or infections than those who had been pregnant but not infected.

Does Covid-19 hurt the baby?

It’s very unlikely that a fetus will be infected with the virus if its mother is. “There’s a pretty strong barrier between the maternal side of the placenta, where mom’s blood is going through and the fetal side where the baby’s blood is going through,” says Prabhu. However, the baby can be affected in other ways. “Often what the baby experiences more commonly is mom’s reaction to an infection.” Campbell explains that this can include temperature swings like fevers, heart rate changes and blood pressure changes. While these changes may not be too dangerous for the mother, “for the baby to continue to grow and thrive, it requires a relatively stable blood pressure to support its own circulation through the umbilical cord.” Without blood flow to deliver nutrients, the fetus’s growth can be restricted.

Early in the pandemic, having Covid-19 during pregnancy barely raised the risk of having a stillbirth. But this summer, Prabhu says that changed. “The risk [of having a stillbirth] was a lot higher with the Delta variant.” Prior to the pandemic, about 0.63 percent of deliveries resulted in a stillbirth. That number stayed relatively flat early in the pandemic, even among those who contracted Covid-19. But when the Delta wave hit, 2.7 percent of pregnancies ended in a still birth among those infected Covid-19 while pregnant, according to a study by the Centers of Disease Control and Prevention (CDC.)

Last week, scientists published a study showing that in the rare occasion that a pregnant person with Covid-19 does experience a stillbirth, the damage that caused it is both extensive and puzzling. “We were trying to determine how and why these fetuses and newborns died and what we found was absolutely unique,” says lead author, David Schwartz, a perinatal pathologist in Atlanta, Georgia.

They weren't dying because the virus had infected their body and was causing damage. Instead, the virus was attacking the mother’s placenta, destroying the protective layer of the placenta, blocking blood flow to the baby, and causing what he described as “a very unusual inflammatory condition.”

How do vaccines affect pregnant individuals and their fetuses?

Getting vaccinated dramatically decreases the chances of severe illness and death from Covid-19, whether a person is pregnant or not. Studies show that pregnant individuals are protected by vaccines. Their bodies mount potent antibody responses, just like individuals who aren’t pregnant, so they are less likely to develop Covid-19 than unvaccinated pregnant women. If they do get Covid-19, they’re less likely to be severely ill.

As for their babies, a June 2021 study showed that 35,691 vaccinated pregnant individuals who submitted data to V-Safe, the CDC’s vaccine adverse event tracking app designed specifically for the Covid-19 vaccines, showed no increased risk of adverse pregnancy-related outcomes such as preterm birth, birth defects and miscarriage.

An important fact to keep in mind, explains Prabhu, is that although it’s rarely discussed, miscarriage occurs in up to 20 percent of pregnancies, with or without a Covid-19 vaccine. “When [a miscarriage] happens to people, they often think they did something wrong. But the reality is that you can't really do anything wrong to cause your miscarriage and miscarriage actually happens in about 15 to 20 percent of all pregnancies.”

Will getting vaccinated during pregnancy protect the baby?

“Parents and moms often want to know, ‘well, is this going to help my baby?’” says Prabhu. Researchers still don’t know how many antibodies a baby needs to be protected from Covid-19, but they do know that at least some antibodies cross the placenta. Campbell explains that “it’s well established that antibodies cross into the placenta” and that those antibodies usually last in the baby’s blood for at least two to three months.

A September 2021 study showed that not only did the babies of vaccinated mothers have antibodies in their blood, but that if the mother had gotten her second vaccine while pregnant, the level of antibodies in her baby’s blood was notably higher than if she’d only received the first shot.

“The babies are getting some antibodies and anything is better than nothing, because the minute they’ve been born the baby has no access to vaccines,” says Prabhu.

In fact, as mentioned in the intro, the CDC announced on February 15 that when pregnant patients got vaccinated, their babies were 60 percent less likely to be hospitalized with Covid-19 in the first six months of their lives.

Will the vaccine make an individual infertile?

“There's absolutely no evidence that vaccination, or booster does compromise fertility,” says Richard Leach, a gynecologist and fertility specialist at Michigan State University. There has been some research suggesting that menstruation can be altered after vaccination. According to a January 2022 study, some women’s menstrual cycles lasted slightly longer after vaccination than before, but, “within two or three months that's been shown to be to go back to normal,” says Leach.

Why haven’t many pregnant individuals gotten vaccinated?

As mentioned earlier, pregnant individuals are usually excluded from clinical trials for most drugs and vaccines, and that didn’t change during the pandemic. That means that when the first data on the safety and efficacy of Covid-19 vaccines was published, “there was a caveat for pregnant women,” says Campbell.

Since definitive data was lacking, the CDC only recommended that pregnant patients discuss the risks and benefits with their physicians before deciding whether or not to get vaccinated. Eventually, in August of 2021, as more data was published on the women who had chosen to get the shot, the CDC and World Health Organization (WHO) officially recommended that pregnant individuals receive the vaccines. But, by then “the messaging around the vaccine was more muddled,” says Campbell. “There was mixed messaging that was received by not only pregnant people, but also health care workers, family members. I think that created an air of caution.”

A social component also contributed to low vaccine uptake among pregnant individuals. “Inadvertently, healthcare workers will take care of pregnant patients in a different way than they would take care of someone who's not pregnant. Their goal is to not do harm, but in doing so, it might delay a diagnosis, for example,” says Campbell, “one clear example of that would be that maybe they defer some type of radiographic imaging for the patient to make a diagnosis, let's say of pneumonia, and where they would get that in a non-pregnant adult without hesitating.”

Prabhu says she understands why pregnant patients have doubts about getting vaccinated. “Women are worried if they get a fever [after vaccination] they’re going to hurt their baby or go into preterm labor.” Luckily, she says, the fevers that pregnant patients get after the shot are “really mild and really low grade and very treatable with a dose of Tylenol, so they are not likely to be harmful.”

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