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COVID-19 Infection Among Asymptomatic Pregnant Women May Be Low, Yale New Haven Study Finds

Tuesday, May 26, 2020

Results have positive implications for PPE use, staff safety, and treatment of new mothers

New Haven, CT (May 26, 2020) – Contrary to fears created by a recently published report, COVID-19 infection among asymptomatic pregnant women admitted to many community hospitals for labor and delivery may be quite low, a new study finds. The report, from experts at Yale New Haven Health, show that less than three percent of asymptomatic pregnant women admitted to three Yale New Haven Health hospitals during April tested positive for COVID-19. Those results stand in stark contrast to the 13.5 percent prevalence found among such patients in a study conducted in New York City, a known epicenter for COVID-19 infection.

The study, which appears as a letter in the May 24 edition of JAMA, was based on a universal coronavirus testing project for patients presenting for childbirth at Greenwich, Bridgeport and Yale New Haven hospitals.

“Our report provides reassuring information on infection rates and appropriate hospital responses outside of highly endemic areas,” said corresponding author Katherine H. Campbell, MD, medical director at Yale New Haven Hospital Labor & Birth and Maternal Special Care Units.

“Not only have we provided insight into the nature of a positive test, we’ve highlighted how a comprehensive testing program can reduce the use of personal protective equipment among labor and delivery staff without increasing their risk of exposure.”

For patients with COVID-19 symptoms, hospital policies require clinicians to wear N95 respirators and appropriate protective equipment until test results are returned, continuing their use for patients with positive test results. For patients without symptoms of COVID-19, clinicians follow usual precautions, including the wearing of standard masks. Of 770 patients who hadn’t previously been diagnosed with COVID-19, only 30 tested positive for COVID-19. Of those, 22 were asymptomatic – meaning the overall prevalence of positive test results among asymptomatic women was 2.9 percent.

Further, no asymptomatic patients who tested negative developed symptoms or required further testing, and no health care workers on the obstetric units were removed from work due to COVID-19 exposure or disease from transmission from a known or possible contact with a patient. The study’s findings are especially significant as hospitals try to use their personal protective equipment judiciously and as the number of women seeking a home birth – which comes with its own risks – has risen.

The study also found that, while the number of asymptomatic women who tested positive grew 10-fold during the study, the number who were symptomatic decreased by half. Christian Pettker, MD, chief of Obstetrics at Yale New Haven Hospital, hailed those findings as positive news, noting that among patients who have recovered, the COVID-19 test can yield positive results for up to six weeks.

“Given our data, we think that a large number of the asymptomatic patients who test positive might not actually be actively infected or infectious,” said Dr. Pettker, also a study author.

“This requires more research but has very important implications for patients who test positive who then might have to be isolated and separated from their babies.” “From a patient standpoint,” he said, “this actually might be even more newsworthy than the point that labor units are much safer than has been reported.”

Yale New Haven Health (YNHHS), the largest and most comprehensive healthcare system in Connecticut, is recognized for advanced clinical care, quality, service, cost effectiveness and commitment to improving the health status of the communities it serves. YNHHS includes five hospitals – Bridgeport, Greenwich, Lawrence + Memorial, Westerly and Yale New Haven hospitals, several specialty networks and Northeast Medical Group, a non-profit medical foundation with several hundred community-based and hospital-employed physicians. YNHHS is affiliated with Yale University and Yale Medicine, the clinical practice of the Yale School of Medicine and the largest academic multi-specialty practice in New England. Yale New Haven Hospital is the primary teaching hospital of Yale School of Medicine.