Objective To evaluate the effectiveness of a multifaceted intervention on practices for prevention, diagnosis and management of postpartum haemorrhage (PPH) and on the prevalence of major PPH in a French perinatal network.Design Quasi-experimental before-and-after survey.Setting All maternity units (n = 19) of a French administrative region, operating as a perinatal network.Sample One representative sample of all women delivering in the network, one representative sample of women with PPH deliveries and an exhaustive sample of women with major PPH. Main outcome measures Practices for prevention, diagnosis and management of PPH and prevalence of major PPH.Results After the intervention, the pharmacological prevention of PPH increased from 58.8% to 75.9% of vaginal deliveries (P < 10 )4 ), and the use of blood collecting bags from 3.9% to 76.3% (P < 10 Conclusions The intervention was effective at improving PPHrelated preventive and diagnostic practices in a perinatal network. Improving management practices and reducing the prevalence of major PPH might require a different intervention design.