Decreased rate of obstetrical anal sphincter laceration is associated with change in obstetric practice.

A study was conducted to describe the rate of obstetrical anal sphincter laceration in a large cohort of women and to identify the characteristics associated with this complication. Data from all vaginal deliveries occurring between January 1996 and December 2004 at one institution were used to compare women with and without anal sphincter lacerations. Among 16,667 vaginal deliveries, 1,703 (10.2%) anal sphincter lacerations occurred. Regression models suggested that episiotomy (OR 1.36; 95% CI 1.16, 1.58), vacuum delivery (OR 3.19; 95% CI 2.69, 3.79), and forceps delivery (OR 2.79; 95% CI 1.94, 4.02) were each associated with the increased risk of anal sphincter laceration. Year of delivery was associated with a decreased risk of anal sphincter laceration (OR 0.94; 95% CI 0.92, 0.96) with the rate of laceration decreasing from 11.2% to 7.9% during the study period. Episiotomy and operative vaginal delivery are significant, modifiable risk factors. Changes in obstetric practice may have contributed to the dramatic reduction in anal sphincter laceration during the study period.