Postpartum haemorrhage (PPH) is an important cause of maternal mortality. We conducted a systematic review of the prevalence of PPH with the objective of evaluating its magnitude both globally and in different regions and settings: global figures, as well as regional, country and provincial variations, are likely to exist but are currently unknown. We used prespecified criteria to select databases, recorded the database characteristics and assessed their methodological quality. After establishing PPH (>or=500 mL blood loss) and severe PPH (SSPH) (>or=1000 mL blood loss) as main outcomes, we found 120 datasets (involving a total of 3,815,034 women) that reported PPH and 70 datasets (505,379 women) that reported SPPH in the primary analysis. The prevalence of PPH and SPPH is approximately 6% and 1.86% of all deliveries, respectively, with a wide variation across regions of the world. The figures we obtained give a rough estimate of the prevalence of PPH and suggest the existence of some variations. For a reliable picture of PPH worldwide - its magnitude, distribution and consequences - a global survey tackling this condition is necessary.