Each of the uniform how to order tables in this article covers one of the distinct time periods. The upper rows (1–3) of these tables show to what extent the excluded patient categories affect the size of the study population and the incidence of both outcome variables. The other rows (4–36) of the tables show how the number of patients (records) and the adverse outcomes within the STAS population are distributed among the main (merged) context related patient groups (figure 1). Number of patients Compared to the reference period (I), period II shows a reduction of the total number of births ≥37 weeks (B1) and also the number of STAS births (B4). The number of STAS

births supervised by the second or third line (B21) remains practically

the same. At the same time, there has been an absolute and relative decline in the number of patients in the excluded categories (B3,C3). Time period III subsequently shows a slight increase in the total number of births (B1), but a further decrease in the number of STAS births (B4). The number of STAS births supervised by the second or third line also shows a slight decline, both absolutely and relatively (B21,C21). This is accompanied by a substantial absolute and relative increase in the number of patients in the excluded categories (B3,C3). All this results in a decrease in the proportion of births supervised by the first line (36.4%, 35.7%, 32%) (C5). Population characteristics In the basic population, the differences in mother, labour and child characteristics between

the three successive time periods are small (table not shown). Exceptions to this are the decrease in the proportion of pregnancies ≥42 weeks in the periods I (5.9%), II (5.3%) and III (3.2%), the decrease in the proportion of breech presentations (4.4%, 4.1%, 3.6%) and the increase in the proportion of deliveries with epidural analgaesia (5.3%, 7.8%, 13.1%). Distribution over the 24 h day In line with our basic assumption, in each of the three time periods the total group of patients who started labour under the supervision of the first line shows a distribution pattern that approximates Drug_discovery the expected distribution of the deliveries over distinct parts of the day (D14,D15,D16). In almost all other (merged) context related patient groups there is a disproportional distribution of patients (records) between the ‘daytime group’ and the ‘evening/night group’. In the group of STAS births supervised by the first line the proportion of the ‘daytime group’ in the periods I (28.3%), II (27.7%) and III (27.2%) (D6) is increasingly smaller than expected (29.2%). At the same time, in the group of referrals during labour this proportion is considerably larger than expected (33.7%, 33.3%, 32.3%) (D10).