A study conducted by investigators at Cedars-Sinai suggests that universal testing of asymptomatic pregnant women in labor may not be necessary at every hospital. The investigation was prompted by reports from several large hospitals in New York City that nearly 14% of asymptomatic women admitted for childbirth had tested positive for COVID-19 during the early weeks of the pandemic. The women did not know they were infected.

In California, infections from the novel coronavirus and deaths from COVID-19 are strikingly lower than those in the state of New York. The reasons for the dramatic differences across regions of the country are not yet clear.

"That data from New York made us very concerned about the possibility of asymptomatic infections among our own pregnant patients. This would have implications for them, their babies, their households and for the health of our staff caring for them," said Mariam Naqvi, MD, maternal-fetal medicine specialist at Cedars-Sinai.

For one week in April, universal testing was employed to study the rates of asymptomatic infection in all admitted pregnant patients at Cedars-Sinai. Of the 82 patients tested, two had symptoms associated with the novel coronavirus, SARS-CoV-2, but 80 women were asymptomatic. The findings of the study were published this week in the journal Obstetrics & Gynecology: Severe Acute Respiratory Syndrome Coronavirus 2 Universal Testing Experience on a Los Angeles Labor and Delivery Unit.

"We had no positive tests for COVID-19 in any of the 80 asymptomatic women in our labor and delivery unit, and all remained symptom-free throughout their hospitalizations. Of the two patients who had symptoms when admitted, one tested positive," said Naqvi, the study's principal investigator.

Sarah Kilpatrick, MD, PhD, chair of the department of Obstetrics and Gynecology, emphasizes how important it is to have accurate data about the number of asymptomatic pregnant women who come to the hospital to give birth and are not infected with the virus.

"If a high number of the asymptomatic women had tested positive for COVID-19, then we would need to continue testing all pregnant women. But as we suspected, the positive tests for asymptomatic women were in fact very low-zero-so we do not need to institute universal testing at this moment," said Kilpatrick, one of the study investigators. "These results are reassuring for our patients, their families and for healthcare providers."

Importantly, sporadic outbreaks or hot spots may develop quickly as the pandemic works its way through cities and states. Kilpatrick says it is critical that hospitals and communities remain vigilant in protecting pregnant women.

"We would restart universal testing immediately if we noted an increase in the number of positive tests among asymptomatic pregnant women in Los Angeles or around the state," Kilpatrick said. "To keep this positive rate low, we all must continue with what is working: wearing face masks, frequent hand-washing and maintaining physical distancing."