The sequence of intrapartum interventions: a descriptive approach to the cascade of interventions.

Purpose: To model the timing and sequence of intrapartum interventions and to estimate the association with labor length and delivery mode.
Methods: A longitudinal multi-center cohort study included data from 3,955 low-risk women who gave birth in hospitals in Lower Saxony, Germany. We analyzed three intrapartum interventions: amniotomy, oxytocin augmentation and epidural analgesia. We divided births into time intervals delineated by these interventions and noted cervical dilation at interval onset. We analyzed the duration of intervals from onset of labor until the first intervention and between intrapartum interventions with Kaplan-Meier's estimate, regarding the three interventions as competing risks. Further, we analyzed the cervical dilation before an intervention by Kaplan-Meier's estimate without censoring.
Results: 73.2 % of the included 2,082 nulliparae (n = 1,525) and 59.6 % of the included 1,873 multiparae (n = 1,117) received at least one intervention, while 1,313 women (33.2 %) experienced a normal labor without any of these interventions. The intervals from onset of labor until the first intervention and from the first until the second intervention were significantly shorter in multiparae than in nulliparae. The intervention cascade in nulliparae most often started with epidural analgesia in early labor (n = 579, 27.8 %). Oxytocin augmentation most often followed after a short interval (n = 343, 59.2 %, median 1.57 h). In multiparae, amniotomy was most often the first intervention (n = 629, 33.6 %), and spontaneous birth most often followed (n = 503, 80.0 %). Labor duration and operative deliveries increased as interventions increased.
Conclusions: The temporal sequence of intrapartum interventions varied in association with parity, cervical dilation, labor duration and mode of birth.