200310014)). This project was submitted for ethical approval and was waived by the Ethical committee of

the no Radboud umc. Provenance and peer review: Not commissioned; externally peer reviewed. Data sharing statement: No additional data are available.
Since its foundation in 1999, Euro-Peristat’s objective has been to monitor and evaluate maternal and child health during the perinatal period using valid and reliable indicators. Owing to the successive Peristat reports,1–3 the perinatal mortality rate has become a widely used indicator to compare the performance of obstetric care systems in the participating European countries. Partly as a result of the greatly increased attention to patient safety since the publication of the influential American report ‘To Err is Human’,4

the perinatal mortality rate is also often used to rule out or reveal differences in the safety of care within an obstetric care system. Thus, over the years, publications from different countries have reported a higher perinatal mortality rate at childbirth outside office hours than at delivery during the day.5–10 What almost all of these comparative studies have in common is that they take only part of the obstetric care system into consideration, have a transversal design, and are based on the data of a rather large number of mostly older calendar years. This poses the question: Is the design of these studies sufficiently consistent with the complexity and the dynamics that characterise

each (obstetrical) care system? Professional organisational context The key concept in this study is the professional organisational context, defined here as the whole of knowledge, skills, organisational arrangements and technical facilities available to optimise the effectiveness and safety of (obstetric) care. The starting point is that the context of pregnancy and childbirth is determined by many interrelated factors. Each of these factors can exhibit incidental or structural deficiencies (whether or not through insufficient use) that contribute to substandard care and adverse outcomes.11 In our approach it is nevertheless essential Cilengitide that we consider the professional organisational context as a whole. This can be done at three levels. At the micro level, it concerns the context of an individual obstetric care process. At this level there are effectively as many professional organisational contexts as there are births. At the meso level, it concerns the context in a specific obstetric unit or ward. The focus of this study is on the macro level, the model-based country-wide context that can be constructed using individual data. It is in the nature of each professional organisational context that it is far from stable.