Anal sphincter tears: prospective study of obstetric risk factors.

OBJECTIVE: To evaluate intrapartum risk factors for anal sphincter tear. DESIGN: A prospective observational study. SETTING: Delivery unit at the University Hospital in Göteborg, Sweden. PARTICIPANTS: 2883 consecutive women delivered vaginally during the period between 1995 and 1997. Information was obtained, from patient records and from especially designed protocols which were completed during and after childbirth. MAIN OUTCOME MEASURES: Anal sphincter (third and fourth degree) tear. RESULTS: Anal sphincter tear occurred in 95 of 2883 women (3.3%). Univariate analysis demonstrated that the risk of anal sphincter tear was increased by nulliparity, high infant weight, lack of manual perineal protection, deficient visualisation of perineum, severe perineal oedema, long duration of delivery and especially protracted second phase and bear down, use of oxytocin, episiotomy, vacuum extraction and epidural anaesthesia. After analysis with stepwise logistic regression, reported as odds ratio, 95% confidence interval, the following factors remained independently associated with anal sphincter tear: slight perineal oedema (0.40, 0.26-0.64); manual perineal protection (0.49, 0.28-0.86); short duration of bear down (0.47, 0.24-0.91); no visualisation of perineum (2.77, 1.36-5.63); parity (0.59, 0.40-0.89); and high infant weight (2.02, 1.30-3.16). Analysis of variance showed that manual perineal protection had a stronger influence on lowering the frequency, and lack of visualisation of perineum and infant weight had a stronger influence on raising the frequency, of anal sphincter tears in nulliparous compared with parous women. CONCLUSIONS: Perineal oedema, poor ocular surveillance of perineum, deficient perineal protection during delivery, protracted final phase of the second stage, parity and high infant weight all constitute independent risk factors for anal sphincter tear. Such information is essential in order to reduce perineal trauma during childbirth.

Birth in standing position: a high frequency of third degree tears.

BACKGROUND: During the past years a major change in the use of delivery position has occurred in Sweden. Recumbent delivery positions have been replaced by a variety of positions: squatting, standing, lateral, kneeling and quadruped. The consequences of this shift in obstetrical practice for development of perineal lacerations are largely unknown. METHOD: Retrospective comparison of uncomplicated deliveries in standing (n = 650) and sitting (n = 264) position with respect to third degree lacerations. RESULTS: The standing and sitting delivery group were similar with respect to maternal, infant and delivery characteristics. The frequency of third degree tears was 2.50% in standing and 0.38% in sitting birth position (p < 0.05). In nulliparous women, third degree tears occurred in 4.2% in standing and 1.0% in sitting position. CONCLUSION: The present data implies that the risk of third degree lacerations is considerably higher (7 x) in standing than in sitting birth positions.