New and expecting mothers are navigating a morass of science and medicine as they try to mitigate the risks of COVID-19 to themselves and their babies.

Why it matters: Pregnancy can be hard during normal times, but there's an extra layer of uncertainty during the pandemic as COVID-19 presents unique risks to pregnant people.

Driving the news: NIAID director Anthony Fauci said Wednesday that roughly 20,000 pregnant people had been vaccinated in the U.S. so far, and no complications have been seen.

• But "it takes us quite a bit of time to follow the woman and her fetus and then her baby and see how things will turn out," Geeta Swamy, associate professor of OB/GYN andan associate vice president for research at Duke, points out.
• The Pfizer BioNTech and Moderna vaccines authorized for use in the U.S. don't use live or attenuated viruses and studies of pregnant animals suggest they are safe, experts say. However, pregnant and lactating people were not included in the initial vaccine trials.
• "No one anticipates that there will be an impact on fetal development or growth," Swamy tells Axios. But some are concerned potential side effects from the vaccine, including fever and inflammation, could stress the fetus.
• "We have good theoretical data and those risks aren’t high, but ultimately individuals have to make that choice and it is hard," says Naima Joseph, who specializes in internal maternal medicine at Emory University's School of Medicine.

Between the lines: This leaves pregnant people to weigh the risks. The CDC doesn't take a stance, stating, "People who are pregnant and part of a group recommended to receive the COVID-19 vaccine may choose to be vaccinated."

On the one hand: Data show pregnant people are at higher risk of developing severe COVID-19 compared to women of the same age who are not pregnant, and there appears to be a risk of preterm birth.

• Pregnant people are "more likely to be hospitalized, to require intensive care, to require ECMO, to be ventilated, and to die, unfortunately," Emory Healthcare's Denise Jamieson told a JAMA webcast Monday.

On the other hand: Clinical trials, including those for COVID-19 vaccines, typically don't include pregnant or lactating people, leaving a gap in knowledge about the effect of one of the most important pandemic-fighting tools.

• Catherine Spong, chief of the Division of Maternal-Fetal Medicine and vice chair of the OB/GYN department at UT Southwestern, told the webcast many experts are "absolutely" disappointed pregnant or lactating people were not included in the phase III trials.
• A congressional task force met for years and came up with recommendations and an implementation plan on how to include these two groups, and "yet, still, again, they were not included in something where they were clearly at higher risk," said Spong, who co-authored a piece in JAMAthis week about COVID-19 vaccination for pregnant and lactating people.

One open question is whether a baby is protected if their pregnant mother is vaccinated.

• Pregnant people are recommended to get the flu and Tdap vaccines because the newborn will have some immunity for the first several months, Swamy said.
• A handful of recent studies, including one by Joseph, found COVID-19 antibodies from infection cross the placenta.
• But antibodies weren't transferred at as high of a rate as "we know the placenta can do" from studies of other pathogens, Joseph says. "We don't know what that means for vaccines yet," but are now conducting studies.

Other pressing questions...

• Can a mother's infection affect the fetus? "We think infection can occur but it is quite rare," Joseph says. "Over a year of data and deliveries, there doesn’t seem to be increased risk for birth defects or anything besides preterm delivery," mostly in people with severe disease.
• Can caretakers like grandparents help out safely? Jamieson and Spong recommend caretakers get vaccinated and wait two weeks after the second shot (for the mRNA vaccines). They should wear masks and practice good hygiene.
• Breastfeeding women can safely get the vaccine, Swamy says, which is supported by the Academy of Breastfeeding Medicine.

What to watch:Pfizer and J&J, which filed for emergency use authorization of its COVID-19 vaccine, plan to begin clinical trials for pregnant people, and the CDC is monitoring all vaccinated people through its v-safe program.

• Moving forward, Joseph says, "the highest priorities are maternal inclusion in studies that look at adaptive immunity because that's the only way to design rational vaccines for this population."