Do pregnancy and COVID-19 vaccines mix? Here’s what the experts say

To vaccinate or not to vaccinate — that is the question pregnant women are asking themselves as COVID-19 shots roll out across the country.

Like so many things involving the pandemic, there are no easy answers. The two vaccines that have received emergency use authorization from the Food and Drug Administration were not tested for safety or efficacy in pregnant women, so there’s no hard data to go on.

The American College of Obstetricians and Gynecologists says the vaccines “should not be withheld from pregnant individuals who meet criteria for vaccination,” such as the healthcare workers who received priority access. The medical group also says that “pregnant patients who decline vaccination should be supported in their decision.”

The Centers for Disease Control and Prevention are in agreement that if pregnant women are eligible for a COVID-19 vaccine, “they may choose to be vaccinated.” But the agency stops short of saying they should.

With as many as 300,000 pregnant women in the nation’s healthcare workforce, it’s a predicament neither patients nor their doctors can afford to ignore. And as vaccine access expands to include people with medical conditions that make them more vulnerable to a severe case of COVID-19, even more women will face the same dilemma.

Both the CDC and ACOG suggest that pregnant women weigh the benefits of a vaccine against the possible risks, noting that the pros and cons may be different for each person. A consultation with a doctor may be helpful, but it should not be required, both organizations say.

The picture is also unclear for women who are trying to become pregnant and for mothers who are breastfeeding. Both ACOG and the CDC agree that COVID-19 vaccines should be available to women in both groups.

Vaccines are routinely given to pregnant women to protect them and their developing babies from diseases like influenza and whooping cough, a pair of obstetricians and gynecologists noted this week in Annals of Internal Medicine. And “few if any vaccines” are considered unsafe for nursing mothers, including the one for measles, mumps and rubella that contains live but weakened viruses.

In the midst of a pandemic that has killed at least 3,000 American women of childbearing age, adding a COVID-19 vaccine to the mix is certainly sensible, wrote Dr. Laura Riley of Weill Cornell Medicine and Dr. Denise Jamieson of Emory University School of Medicine.

The clinical trials conducted by Pfizer and Moderna may offer some reassurance to pregnant women who are leaning toward vaccination.

Both vaccine makers gave pregnancy tests to women of childbearing age so they could be excluded from their Phase 3 trials. Nevertheless, three dozen pregnant women got in — either their pregnancies were too early to trigger a positive test result, or they conceived shortly after receiving their first dose.

The Pfizer clinical trial included 12 pregnant women who received the vaccine and 11 who got the placebo. At least one of the volunteers in the placebo group had a miscarriage, according to a report by FDA scientists who reviewed Pfizer’s clinical trial data. No miscarriages or other pregnancy-related problems were reported by volunteers who got the vaccine.

Another 13 pregnant women were enrolled in Moderna’s clinical trial; six of them got the vaccine and seven got the placebo. Among the women in the placebo group, one had a miscarriage and another had an elective abortion, FDA scientists reported. None of the women in the vaccine group reported any problems related to their pregnancies.

In both cases, “there are currently insufficient data to make conclusions about the safety of the vaccine” in pregnant women, FDA scientists concluded.

Moderna scientists conducted toxicity tests in rats, giving their vaccine to the animals shortly before they mated and to others that were already pregnant. The shots didn’t affect the rats’ fertility or the development of their pups, the FDA scientists found. Although some of the pups were born with “skeletal variations,” these are common and usually resolve on their own without any need for treatment, the scientists added.

ACOG said it expects the two COVID-19 vaccines to be about as safe and effective for pregnant women as they are for other people. However, the OB/GYN group acknowledged that without hard data, “the potential risks to a pregnant individual and the fetus are unknown.”

(ACOG lobbied to have pregnant women included in the initial Phase 3 clinical trials. Although that didn’t happen, trials involving pregnant women are planned for the future, the organization noted.)

There are good reasons for pregnant women to get vaccinated. Although the risk of a severe case of COVID-19 is low for any woman of childbearing age, studies suggest that a COVID-19 patient who is pregnant is more likely to be admitted to a hospital’s intensive care unit, more likely to require breathing assistance from a mechanical ventilator, and more likely to die of the disease.

About 1% of pregnant women in the U.S. have required ICU care for COVID-19, and out of every 1,000 pregnant woman who develop COVID-19, 1.5 have died, Riley and Jamieson wrote in Annals.

Pregnant women with COVID-19 may also be at increased risk of delivering their babies prematurely or requiring a cesarean section, among other problems.

“Thus, it is critical that pregnant persons have the opportunity to be vaccinated if they would otherwise meet the criteria for vaccination,” the doctors wrote.

There’s no biological reason to fear that either the Pfizer-BioNTech or Moderna vaccine will make a pregnant woman sick, ACOG says.

Neither of these vaccines are made with an actual coronavirus, so there’s no chance that it will cause an infection. Neither includes an adjuvant — an ingredient to help produce longer-lasting immunity — that might be dangerous to mother or fetus. And although they deliver the genetic instructions for cells to make a small piece of the coronavirus so that the immune system can make antibodies, the vaccines do not alter the recipient’s DNA.

There’s also no need for women to take a pregnancy test before getting a COVID-19 vaccine, ACOG and CDC agree. Nor is there any reason for a woman who’s been vaccinated to avoid getting pregnant, they add.

The OB/GYN group advises women to get vaccinated even if they are “actively trying to become pregnant.” Both ACOG and the CDC agree that it’s not necessary to delay or avoid pregnancy after getting both doses of either the Pfizer or Moderna vaccine.

New mothers who are breastfeeding have even less data to go on when it comes to COVID-19 vaccines. The CDC advises breastfeeding women who want to get vaccinated to go ahead and do so, and ACOG agrees that nursing mothers should be eligible for the vaccines. The benefits of immunization are real, and they’re not outweighed by any “theoretical concerns” about vaccine risks, the group says.