Objective: In Norway, we have experienced a gradual increase in the incidence of obstetric anal sphincter injuries from under 1% in the late 1960s to 4.3% in 2004. This study was aimed to assess whether an interventional program causes a decrease in the frequency of anal sphincter tears.
Methods: In all, 40,152 vaginal deliveries between 2003 and 2009 were enrolled in the interventional cohort study from four Norwegian obstetric departments. The focus of the intervention was on manual assistance during the final part of the second stage of labor. Data were analyzed in relation to occurrence of obstetric anal sphincter tears.
Results: The proportion of parturients with anal sphincter tears decreased from 4-5% to 1-2% during the study period in all four hospitals (P<.001). The tears associated with both noninstrumental and instrumental deliveries decreased dramatically. The number of patients with grades 3 and 4 anal sphincter ruptures decreased significantly, and the reduction was most pronounced in grade 4 tears (-63.5%) and least in 3c tears (-47.5%) (both P<.001). The number of episiotomies increased in two hospitals but remained unchanged in the other two. The lowest proportion of tears at the end of the intervention (1.2% and 1.3%, respectively) was found in the two hospitals with an unchanged episiotomy rate.
Conclusion: The multicenter intervention caused a highly significant decrease in obstetric anal sphincter injuries.
Level of evidence: II.