This levelling of incidence differences between the parts of the day is accompanied

by an increase in incidence in most ‘daytime groups’ (V,W). Discussion By developing a descriptive inhibitor Rapamycin model, we have produced a tool that can be helpful in the systematic monitoring and evaluation of care in the obstetric care system. Even if the attention is focused on a part of the obstetric care system, the entire system remains in view. In this respect, our study design distinguishes itself from many other studies in this area.5–10 Yet there are more relevant differences. The design of the model is based on the most relevant organisational characteristics of the obstetric care system. In view of the system’s dynamics we have opted for a combination of a transversal and a longitudinal study approach, while deliberately limiting the number of calendar years per distinct time period. A major limitation of this study is related to the common macro approach. The figures compared at the macro level consist of the sum of the figures that are collected at the meso level. This complicates the interpretation of the results. Small differences in the relative incidence

of adverse outcomes at the macro level may hide much larger, in part mutually compensating, differences at the meso level. However, such a difference may equally well point to shortcomings in just a few units and/or wards. Diverging outcome variables Compared to the reference period, particularly

in the most recent time period (2008–2010), the relative incidence of perinatal mortality in the term population is greatly diminished. In the STAS population this decline mainly concerns the ‘evening/night groups’ and the ‘duty handover groups’ (figure 3). As a result, there are hardly any demonstrable differences any more in the relative incidence of perinatal mortality between the parts of the day. It follows that such differences can no longer be used to question the safety of obstetric care outside office hours in the Netherlands.8 16 Figure 3 Development of adverse outcomes in Spontaneous onset of labour, after reaching the Term Carfilzomib period, Alive at the onset of labour, Single child (STAS) births supervised by 2nd/3rd line. In contrast to the perinatal mortality rate, the incidence of the Apgar score <7 barely shows a decline in the successive time periods (figure 3). In most ‘daytime groups’ the levelling of the differences in incidence between the parts of the day is even accompanied by a slight rise in incidence. It is noteworthy that in the group of teaching hospitals with a NICU in the most recent time period, there has been an increase in the incidence of the Apgar score <7 during all parts of the day. It is not yet clear how this remarkable divergence of both outcome variables should be explained. The question of whether the quality of obstetric care in hospitals has improved, therefore, cannot be answered unequivocally.