ObjectiveThe WHO Safe Childbirth Checklist (SCC) is a promising initiative for safety in childbirth care, but the evidence about its impact on clinical outcomes is limited. This study analysed the impact of SCC on essential birth practices (EBPs), obstetric complications and adverse events (AEs) in hospitals of different profiles.DesignQuasi-experimental, time-series study and pre/post intervention.SettingTwo hospitals in North-East Brazil, one at a tertiary level (H1) and another at a secondary level (H2).Participants1440 women and their newborns, excluding those with congenital malformations.InterventionsThe implementation of the SCC involved its cross-cultural adaptation, raising awareness with videos and posters, learning sessions about the SCC and auditing and feedback on adherence indicators.Primary and secondary outcome measuresSimple and composite indicators related to seven EBPs, 3 complications and 10 AEs were monitored for 1 year, every 2 weeks, totalling 1440 observed deliveries.ResultsThe checklist was adopted in 83.3% (n=300) of deliveries in H1 and in 33.6% (n=121) in H2. The hospital with the highest adoption rate for SCC (H1) showed greater adherence to EBPs (improvement of 50.9%;p<0.001) and greater reduction in clinical outcome indicators compared with its baseline: percentage of deliveries with severe complications (reduction of 30.8%;p=0.005); Adverse Outcome Index (reduction of 25.6%;p=0.049); Weighted Adverse Outcome Score (reduction of 39.5%;p<0.001); Severity Index (reduction of 18.4%;p<0.001). In H2, whose adherence to the SCC was lower, there was an improvement of 24.7% compared with before SCC implementation in the composite indicator of EBPs (p=0.002) and a reduction of 49.2% in severe complications (p=0.027), but there was no significant reduction in AEs.ConclusionsA multifaceted SCC-based intervention can be effective in improving adherence to EBPs and clinical outcomes in childbirth. The context and adherence to the SCC seem to modulate its impact, working better in a hospital of higher complexity.