The prevalence of anal sphincter injury in primiparous women.

Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology

PubMedID: 23576493

Guzmán Rojas RA, Shek KL, Langer SM, Dietz HP. The prevalence of anal sphincter injury in primiparous women. Ultrasound Obstet Gynecol. 2013;.
OBJECTIVE: To determine the prevalence of obstetric anal sphincter injuries (OASIS) in a cohort of primiparous women and to evaluate its association with demographic, obstetric and ultrasound parameters. METHODS: A retrospective analysis of the ultrasound volume datasets of 320 primiparous women, acquired at 5?months postpartum. Tomographic ultrasound imaging (TUI) was used to evaluate the external anal sphincter (EAS). A significant EAS defect was diagnosed if a defect of >30(o) was seen in =4 of 6 TUI slices bracketing the EAS. RESULTS: Significant EAS defects were found in 69 women (28% of those delivered vaginally). In 9 of those a 3(rd) degree tear was diagnosed intrapartum and was sutured. In 60 women with significant defects there was no documentation of sphincter damage at birth, implying unidentified or occult defects (60/69, 87%). Among them, 29 had had a 2(nd) degree tear, two a 1(st) degree tear and three an intact perineum. In 31 cases an episiotomy had been performed, with five extensions to a 3(rd) degree tear. On multivariate analysis only forceps was significantly associated with OASIS. CONCLUSIONS: In this cohort of primiparous women we found OASIS in 28% of vaginally parous women, and most had not been diagnosed in Delivery Suite. There seems to be a need for better education of Labour Ward staff in the recognition of OASIS. On the other hand, it is conceivable that some defects may be masked by intact tissue. The significance of such defects remains doubtful. Forceps was the only identifiable risk factor.