Objective To describe the prevalence of overall and asymptomatic SARS-CoV-2 infection in pregnant women admitted for delivery at 3 maternity units in North Wales. Design A prospective multicentre cohort study of universal testing for SARS-CoV-2 infection offered to all pregnant women admitted for delivery. Setting 475 women admitted for delivery in 3 maternity units in North Wales at Bangor, Bodelwyddan and Wrexham between 3rd June and 2nd July 2020. Population 95.8% (n=475) of all women admitted for delivery. Methods Testing performed by reverse transcription-polymerase chain reaction of nasopharyngeal swabs with concurrent universal screening for signs and symptoms of COVID-19 infection. Main Outcome Measures Overall and asymptomatic prevalence of SARS-CoV-2 infection in pregnant women admitted for delivery. Results The overall prevalence of SARS-CoV-2 infection in pregnant women in North Wales was 2.74% with an asymptomatic prevalence of 1.89%. 69% of women infected with SARS-CoV-2 at delivery were asymptomatic. Conclusions Pregnant women with SARS-CoV-2 infection are not reliably identified using symptom and temperature screening as most infected women are asymptomatic on admission. The prevalence of maternal infection and asymptomatic carrier rates vary based on geographic differences in disease prevalence. It is suggested that a trial period of universal testing may help determine whether such an approach is appropriate for an individual maternity unit. Funding – None Key words Universal testing, SARS-CoV-2, COVID-19, pregnant women, delivery