Initial findings of universal screening for SARS-CoV-2 in women admitted for delivery in North Wales: a prospective multicentre cohort study.

We describe the prevalence of overall and asymptomatic SARS-CoV-2 infection in pregnant women admitted for delivery at three maternity units in North Wales. This was a prospective, multicentre cohort study of universal testing for SARS-CoV-2 infection offered to all pregnant women admitted for delivery. Four hundred and seventy-five women were tested by reverse transcription-polymerase chain reaction of nasopharyngeal swabs with concurrent universal screening for signs and symptoms of COVID-19 infection. The overall prevalence of SARS-CoV-2 infection in pregnant women in North Wales was 2.74% with an asymptomatic prevalence of 1.89%. Sixty-nine percent of infected women were asymptomatic. Pregnant women with SARS-CoV-2 infection are not reliably identified using symptom and temperature screening. The prevalence of maternal infection and asymptomatic carrier rates vary within small geographical regions. It is suggested that a trial period of universal testing may help determine whether such an approach is appropriate for an individual maternity unit.Impact Statement The mean incubation period for SARS-CoV-2 is five days and viral shedding may begin two to three days before the appearance of symptoms. Asymptomatic carriers contribute to transmission of the disease. More than two-thirds of infected women were asymptomatic in this study contributing to the body of evidence that most infected pregnant women are asymptomatic. This study provides prevalence data for a rural geographical location in Wales with results similar to an urban London region. There was wide variation in prevalence across three maternity units in a small geographical area ranging from 1.68% to 4.43%. This study supports the recommendations of universal SARS-CoV-2 testing for women attending for delivery regardless of symptom status. The results highlight that prevalence of infection amongst pregnant women cannot be assumed based on geographical location or demographics. A trial period of universal testing would establish local prevalence and helps determine whether such an approach is appropriate for an individual maternity unit. Future research could be directed to the prevalence of virus variants in pregnant populations.