A new study is highlighting the need for more COVID-19 testing for pregnant women about to give birth.

According to a letter by researchers published Monday in the New England Journal of Medicine, more than 1 in 8 asymptomatic women tested in a study on delivery wards at Columbia University Irving Medical Center and the New York-Presbyterian Allen Hospital in New York City test positive for COVID-19.

This means that mothers and their caregivers may not know that they have the virus, and can’t take the necessary precautions against it. The scientists behind this research say all pregnant women about to deliver should be tested.

The four doctors behind the research write: “The potential benefits of a universal testing approach include the ability to use Covid-19 status to determine hospital isolation practices and bed assignments, inform neonatal care, and guide the use of personal protective equipment. Access to such clinical data provides an important opportunity to protect mothers, babies, and health care teams during these challenging times.”

They looked at 215 pregnant women who gave birth at the two New York hospitals between March 22 and April 4. Four who tested positive for coronavirus when admitted had symptoms, but 29 other moms who tested positive were not showing symptoms.

This is important because it is thought that mom-to-baby transmission of coronavirus happens after birth, not in utero.

This follows another study of 43 pregnant women that was published in the American Journal of Obstetrics & Gynecology last week. It examined cases at Columbia University Medical Center in New York and found that most pregnant women (around 80%) who have COVID-19 have only a mild case and don’t get severe symptoms.

That is obviously very good news, but the researchers still underscore the need for testing of all mothers about to give birth in order to prevent the spread of the virus.

If you think you may have COVID-19, talk to your health care team.