When the COVID-19 pandemic began, physicians could only speculate how the virus would affect at-risk patients. For many months, no one had definitive data on how pregnant women might be affected by COVID-19 or the coronavirus vaccines. According to the research journal Nature, a few facts have emerged about the relationship between pregnancy and COVID-19.

One American obstetrician, Yalda Afshar, has led the charge to gather data. She was pregnant herself when the COVID-19 pandemic first began, and that inspired her to create a registry for pregnant women to help scientists monitor the impact of the virus.

After a year of gathering data, Afshar and other scientists have determined that pregnant women are at greater risk of severe complications from COVID-19. Compared to other women their age, pregnant women are more likely to be hospitalized due to COVID-19 and more likely to face long-term issues from the virus. As the Centers for Disease Control have previously reported, women of color are more likely to die from pregnancy than white women, and this trend has continued, as pregnant women of color seem to be more affected by COVID-19.

The babies themselves rarely become sick from COVID-19. Lab work has shown that the virus is not often passed from mother to baby. Doctors still recommend breastfeeding, even for women who have tested positive for the virus. However, pregnant women with COVID-19 are more likely to deliver early, which could cause health issues for their babies.

Due to ethical concerns, no pregnant women were allowed to enroll in the clinical trials for COVID-19 vaccines. While there are no data on how the vaccines might impact pregnant women, most obstetricians, and fetal-maternal specialists recommend that women discuss the vaccine with their providers. Globally, no governments have prioritized vaccine delivery to pregnant or lactating women.

Given the lack of data available, some scientists are calling for reforms to traditional research study guidelines. To these researchers, the protections that keep pregnant women from research studies are paternalistic and harmful. A handful of recent vaccine trials have included pregnant women, but the data from these trials are not yet available, and there’s no indication that overall research guidelines will be changed in the near future.