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A new study showed that some women who delivered babies in the city in recent weeks had been inflicted with the coronavirus without displaying symptoms.

NewYork-Presbyterian and Columbia University Medical Center screened more than 200 women for the illness upon admission between March 22 and April 4, according to the study.

Among the 33 patients who tested positive, 29 of them had no symptoms.

One patient with a swab that was negative for SARS-CoV-2 on admission became symptomatic after giving birth, and was tested again 3 days after the initial test.

SARS-CoV-2 is the severe acute respiratory syndrome that causes COVID-19.

The first diagnosed case of COVID-19 in an obstetrical patient was on March 13, 2020, according to doctors in the study.

The study, doctors claim, underscores the risk of COVID-19 among asymptomatic obstetrical patients. It also warns the true prevalence of infection may be underreported because of false-negative results of tests to detect SARS-CoV-2.

“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,” the study says.

“Access to such clinical data provides an important opportunity to protect mothers, babies, and health care teams during these challenging times.”