To identify cases of severe maternal morbidity (SMM) during pregnancy and childbirth, their characteristics, and to test the feasibility of scaling up World Health Organization criteria for identifying women at risk of a worse outcome. Multicentre cross-sectional study. Twenty-seven referral maternity hospitals from all regions of Brazil. Cases of SMM identified among 82 388 delivering women over a 1-year period. Prospective surveillance using the World Health Organization's criteria for potentially life-threatening conditions (PLTC) and maternal near-miss (MNM) identified and assessed cases with severe morbidity or death. Indicators of maternal morbidity and mortality; sociodemographic, clinical and obstetric characteristics; gestational and perinatal outcomes; main causes of morbidity and delays in care. Among 9555 cases of SMM, there were 140 deaths and 770 cases of MNM. The main determining cause of maternal complication was hypertensive disease. Criteria for MNM conditions were more frequent as the severity of the outcome increased, all combined in over 75% of maternal deaths. This study identified around 9.5% of MNM or death among all cases developing any severe maternal complication. Multicentre studies on surveillance of SMM, with organised collaboration and adequate study protocols can be successfully implemented, even in low-income and middle-income settings, generating important information on maternal health and care to be used to implement appropriate health policies and interventions. Surveillance of severe maternal morbidity was proved to be possible in a hospital network in Brazil.123