Objectives The burden of undocumented SARS-Cov-2 infections in Portuguese pregnant women is unknown. At our institution, routine COVID-19 testing was implemented from 19th of March on to all pregnant women who were admitted for delivery. The purpose of the study was to estimate the SARS-CoV-2 infection rate in our obstetric population admitted for delivery. Mathods Between 19th March and May 4th, 184 pregnant women were screened for SARS-CoV-2 infection upon admission. Results Eleven women were positive for SARS-CoV-2, corresponding to a global prevalence of 6.0%. Of these, only two reported symptoms at admission. The prevalence of asymptomatic infection was 4.9%. We report a lower rate of positive cass than other studies. Eighty-two percent of our cases had no symptoms at admission. Conclusions The proportion of asymptomatic infection highlights the importance of universal laboratory screening for all women admitted for delivery as opposed to symptom-based screening.