(CNN) Most of the pregnant women in New York who tested positive for the novel coronavirus were asymptomatic when they delivered, according to a letter published in the New England Journal of Medicine.

More than one in eight of the asymptomatic patients admitted for delivery tested positive for coronavirus, the research conducted at Columbia University Irving Medical Center and the New York-Presbyterian Allen Hospital found, making a case for testing all admitted pregnant patients.

Knowing if someone is infectious would help hospitals determine where to place the patients so they won't get other people sick and would help guide decisions on what personal protective equipment the staff may need amid a strain on supplies. The research shows the benefits of conducting a universal test on patients, the authors argued in the letter published Monday. Knowing if someone is infectious would help hospitals determine where to place the patients so they won't get other people sick and would help guide decisions on what personal protective equipment the staff may need amid a strain on supplies.

Columbia University Irving Medical Center put a universal testing policy in place for all women admitted for delivery after the medical centers had two coronavirus cases confirmed among their patient population.

Of the 215 pregnant women who delivered at these hospitals between March 22 and April 4, four who tested positive for coronavirus when admitted for delivery had a fever or some other symptoms of the coronavirus.

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