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Objective: To estimate the ability of an intensive interventional program to decrease the number of obstetric anal sphincter injuries (OASIS), while simultaneously decreasing the rate of Caesarean sections (CS).

Study design: The intervention, which aimed at decreasing the number of OASIS, started with a compulsory tutorial for all the midwives and physicians. At the same time, the clinic initiated a program to decrease the number of CS. We compared the outcomes before and after the intervention by calculating the risk ratios with 95% confidence intervals. The changes in selected outcomes were also tested using the test of relative proportions. The follow-up was extended for 1 year after the intervention.

Results: The number of deliveries by CS decreased significantly, as did the number of OASIS in all the subgroups, except for the multi-parous women. The rate of OASIS for instrumental deliveries (mostly by vacuum) decreased significantly (p < 0.003), as compared to pre-interventional period. The number of Grade 4 tears decreased significantly: from 0.4 ruptures per 100 deliveries before the start of the intervention to 0.1 ruptures after the start of the intervention (RR 0.37, 95% CI 0.14-0.98, p = 0.037). However, the OASIS and Grade 4 sphincter injuries increased with forceps delivery. The CS rate decreased from 17.7 to 15.0 per 100 deliveries (RR 0.85, 95% CI 0.78-0.93). The post-interventional follow-up period revealed a further decrease in the frequency of OASIS (to 1.28%, p < 0.001) and a stable CS rate (14.2%).

Conclusion: The intervention significantly decreases the frequency of OASIS, in line with the results obtained for earlier interventions. At the same time, a decrease in CS rate was obtained. (C) 2018 Elsevier B.V. All rights reserved.