Third-degree perineal tears: risk factors and outcome after primary repair

This study aimed to determine the incidence of obstetric anal sphincter tears and to determine the risk factors and outcome after primary repair. This was an audit of third- and fourth-degree tears in 1997-99, occurring in a tertiary obstetric unit with 5000 deliveries per annum. The study involved 75 women with a third-degree tear occurring between 1997 and 1999. A total of 10,307 women delivered vaginally without third-degree tear during this period, and they acted as controls. Obstetric risk factors for tears and the number of patients with ongoing symptoms after repair were studied. Cases were identified from the hospital database. Notes were reviewed to obtain clinical data. Odds ratios were calculated for potential risk factors. The incidence of sphincter tears was 0.6%. The mean age was 27 years and mean birth weight 3532 g; 72% were primiparous and 72% had a spontaneous vaginal delivery. A total of 68% of repairs were performed in theatre, and 76% of repairs were carried out under general or regional anaesthesia. Identified risk factors were nulliparity (OR 1.83), mediolateral episiotomy (OR 2.58), and forceps delivery (OR 3.81); 78% of patients attended for follow-up in the perineal clinic. Forty-four per cent of these women were symptomatic and 75% of the women had evidence of anal sphincter defect on ultrasound. The incidence of obstetric sphincter injury was similar to reports in the literature. Forceps and episiotomy were significant risk factors. Obstetric sphincter injury is associated with significant morbidity as 44% of our patients were symptomatic after repair.