As coronavirus vaccinations begin in the U.S., and a second vaccine nears approval, guidance surrounding pregnant women has shifted.
According to Illinois and U.S. medical experts, pregnant women were excluded from trials for the vaccine, so there is little information on the vaccines' safety for that group.
"We don't have any information actually in pregnancy. Women who were in the trial who became pregnant were removed from the trial so we can't give any information about pregnancy," said Illinois Department of Public Health Director Dr. Ngozi Ezike.
Dr. Anthony Fauci noted last week in a discussion sponsored by Columbia University that pregnant women have not been included in any COVID vaccine clinical trials to date, but "those studies will probably start in mid- to late-January.”
Thirteen pregnancies were reported in Moderna's trial through Dec. 2, with six in the vaccine group, the FDA has said. The company is tracking all women who got pregnant after receiving the vaccine or who were pregnant when they were immunized but didn't know, according to the agency.
Guidance released by the Centers for Disease Control and Prevention states that if a woman is part of a group recommended to receive a COVID-19 vaccine and is pregnant, she may choose to be vaccinated. A discussion with her healthcare provider can help her make an informed decision, the agency stated.
According to the CDC, while no studies have been done so far, "based on how mRNA vaccines work, experts believe they are unlikely to pose a risk for people who are pregnant."
That guidance differs from Great Britain, where pregnant women and women who are breastfeeding were told not to get the vaccine.
"There's a lot of conversation and controversy and advocacy around what to do with women who are pregnant or may become pregnant or breastfeeding," said Dr. Allison Bartlett, associate professor of pediatric infectious diseases at the University of Chicago. "And it's a really interesting issue because pregnant women were excluded from the study. And we understand because we sort of treat pregnant women as a special class, but so much of our health care workforce and our other frontline workers are women of childbearing age that to deny them the ability to get the vaccine just because we don't know is really putting them at a disadvantage."
Vaccine expert, Dr. Paul Offit, who served on the Food and Drug Administration's vaccine advisory panel, said he was "pleasantly surprised" by the guidance surrounding pregnant women.
"There's really no biological reason to think that it would be damaging to either them because they're pregnant or to their unborn child."
He noted, however, one "caveat," which is the potential side effect of a fever.
"High fevers in pregnancy can be deleterious to the unborn child," he said. "So were one to have a high fever associated with the vaccine - and that doesn't seem to be the problem- you can get fevers but typically low-grade fevers, that one could reasonably treat that then with an anti-fever medicine. And same for breastfeeding women, that again, there's really no biological reason to think that one can't breastfeed if getting this vaccine."
Still, pregnant women who contract coronavirus could suffer potentially severe infections, Offit said, "so that's the other side of not getting the vaccine."
Dr. David Martin, vice president for drug safety at Moderna, has said the company plans to establish a "pregnancy registry" to track how its vaccine performs in pregnant women.