Part 2
The 25 delivery units participating in the study, accounted for 82.1% of the deliveries in Norway (Tab. 1, Fig. 2).
The characteristic of the birth population from participating and non-participating units revealed minor, but statistically significant differences in maternal age, pre-pregnancy BMI, parity, start of labour, gestational age at delivery, and transfer to the neonatal intensive care unit (Tab. 1). The categorization of the entire birth population according to the TGCS (which is standard practice in (Norway) is shown in Tab. 2, and of those the groups 1, 2a, 3, 4a and 5 were included in the study. Of eligible women, 8.7% had missing data due to missing study forms (Fig. 2).
The CSs were classified according to the classification and within the study group shown in Figure 4 (Supplement 3). In both nulliparous and parous women (without a previous CS), induction of labour (Group 2a and 4a) compared to spontaneous onset of labour (Group 1 and 3) was associated with a significant higher proportion classified as CS for fetal indication (no oxytocin), dystocia-inefficient uterine action-oxytocin-poor response and dystocia-inefficient uterine action- oxytocin-inability to treat fetal intolerance (Fig. 4, Supplement 3). In women with a previous CS, induction of labour (Group 5b) compared to spontaneous start of labour (Group 5a) was associated with a higher proportion of CS classified as dystocia-inefficient uterine action-oxytocin-poor response and dystocia-inefficient uterine action-inability to treat-fetal intolerance. The prevalence of CS classified as dystocia-efficient uterine action (CPD or malposition) was generally low in all groups. In dystocic labour in women with a previous CS (Group 5) there was a greater prevalence of CS classified as dystocia-inefficient uterine action-no oxytocin compared to the remaining study population (Groups 1-4) (Fig. 4, Supplement 3).