A policy of universal screening of pregnant women for the COVID-19 virus identified a high proportion of women who tested positive and were asymptomatic, based on data from 215 pregnant women in New York City.

This transmission electron microscope image shows SARS-CoV-2—also known as 2019-nCoV, the virus that causes COVID-19. isolated from a patient in the U.S., emerging from the surface of cells cultured in the lab. Courtesy NIAID-RML

This transmission electron microscope image shows the virus that causes COVID-19 emerging from the surface of cells cultured in the lab.

“The obstetrical population presents a unique challenge during this pandemic, since these patients have multiple interactions with the health care system and eventually most are admitted to the hospital for delivery,” wrote Desmond Sutton, MD, and colleagues at Columbia University Irving Medical Center, New York

In a letter published in the New England Journal of Medicine, the researchers reviewed their experiences with 215 pregnant women who delivered infants during March 22–April 4, 2020, at the New York–Presbyterian Allen Hospital and Columbia University Irving Medical Center. All the women were screened for symptoms of the COVID-19 infection on admission.

Overall, four women (1.9%) had fevers or other symptoms on admission, and all of these women tested positive for the virus that causes COVID-19. The other 211 women were afebrile and asymptomatic at admission, and 210 of them were tested via nasopharyngeal swabs. A total of 29 asymptomatic women (13.7%) tested positive for COVID-19 infection.

“Thus, 29 of the 33 patients who were positive for SARS-CoV-2 at admission (87.9%) had no symptoms of COVID-19 at presentation,” Dr. Sutton and colleagues wrote.

Three of the 29 COVID-19-positive women who were asymptomatic on admission developed fevers before they were discharged from the hospital after a median stay of 2 days. Of these, two received antibiotics for presumed endomyometritis and one patient with presumed COVID-19 infection received supportive care. In addition, one patient who was initially negative developed COVID-19 symptoms after delivery and tested positive 3 days after her initial negative test.

“Our use of universal SARS-CoV-2 testing in all pregnant patients presenting for delivery revealed that at this point in the pandemic in New York City, most of the patients who were positive for SARS-CoV-2 at delivery were asymptomatic,” Dr. Sutton and colleagues said.

Although their numbers may not be generalizable to areas with lower infection rates, they highlight the risk of COVID-19 infection in asymptomatic pregnant women, they noted.

“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,” they concluded.

Continuing challenges

“What I have seen in our institute is the debate about rapid testing and the inherent problems with false negatives and false positives,” Catherine Cansino, MD, of the University of California, Davis, said in an interview. “I think there is definitely a role for universal testing, especially in areas with high prevalence,” and the New York clinicians have made a strong case.

Dr. Catherine Cansino is an associate clinical professor in the department of obstetrics and gynecology at the University of California, Davis.

Dr. Catherine Cansino

However, the challenge remains of obtaining quick test results that would still be reliable, as many rapid tests have a false-negative rate of as much as 20%, noted Dr. Cansino, who was not involved in the New York study.

Her institution is using a test with a higher level of accuracy, “but it can take several hours or a day to get the results,” at which point the women may have gone through labor and delivery and been in contact with multiple health care workers who have used personal protective equipment accordingly if they don’t know a patient’s status.

To help guide policies, Dr. Cansino said that outcome data would be useful. “It’s hard to know how outcomes are different, and it would be good to know how transmission rates differ between symptomatic carriers and those who are asymptomatic.”

“As SARS-CoV-2, the virus responsible for COVID-19, continues to spread, pregnant women remain a unique population with required frequent health system contacts and ultimate need for delivery,” Iris Krishna, MD, of the Emory Healthcare Network in Atlanta, said in an interview. “This report in a high prevalence area demonstrated 1 out of 8 asymptomatic pregnant patients presenting for delivery were SARS-CoV-2 positive, illustrating a need for universal screening.

Dr. Iris Krishna of the Emory Healthcare Network in Atlanta

Dr. Iris Krishna

“As this pandemic evolves, we are learning more and more, and it is important to expand our understanding of asymptomatic transmission and the risk this may pose,” said Dr. Krishna, who was not part of the New York study.

“Key benefits to universal screening are the capability for labor and delivery units to implement best hospital practices in their care of mothers and babies, such as admitting positive patients to cohort units,” she noted. Such units would “allow for closer monitoring of mothers and babies, as well as ensuring proper use of personal protective equipment by health care teams” and also would help preserve supplies of personal protective equipment.

Dr. Krishna cited hospital testing capacity as an obvious barrier to universal screening of pregnant women, as well as factors including the need for additional protective equipment to be used during swab collection. Also, “If you get a negative result and there is a strong suspicion for COVID-19 infection, when do you retest?” she asked. “These are key questions or areas of assessment that should be considered before embarking on universal screening for pregnant women.” In addition, some patients may refuse testing out of fear of stigma or separation from their newborn.

“Implementing an ‘opt out’ approach to screening is encouraged, whereby a patient is informed that a test will be included in standard preventive screening, and they may decline the test,” Dr. Krishna said. “Routine, opt-out screening approaches have proven to be highly effective as it removes the stigma associated with testing, fosters earlier diagnosis and treatment, reduces risk of transmission, and has proven to be cost effective. Pregnant women should be reassured that universal screening is beneficial for their care and the care of their newborn baby,” she emphasized.

“Institutions should consider implementing universal screening on labor and delivery as several geographic areas are predicted to reach their peak time of COVID-19 transmission, and it is clear that asymptomatic individuals continue to play a role in its transmission,” Dr. Krishna concluded.

Dr. Sutton and associates had no financial conflicts to disclose. Neither Dr. Cansino nor Dr. Krishna had any financial conflicts to disclose. Dr. Cansino and Dr. Krishna are members of the Ob.Gyn. News Editorial Advisory Board.

SOURCE: Sutton D et al. N Engl J Med. 2020 Apr 13. doi: 10.1056/NEJMc2009316.