Obstetric anal sphincter rupture in older primiparous women: a case-control study

To determine if maternal age (35 years of age or older) in primiparous women is a risk factor for the development of obstetric anal sphincter rupture (OASR) and to identify obstetric factors associated with it.

This is a retrospective case-control study. The study population was made up of the 5,345 primiparous women aged 24-45 years who delivered vaginally with singleton live-born neonates during 1990-99 at the Department of Obstetrics and Gynecology, Linköping University Hospital, Sweden. As cases the 327 primiparous women aged 35-45 years at delivery were selected. For each case two primiparous controls ten years younger were selected, matched for gestational age and year of delivery, in all 654 controls. Maternal, obstetrical, and neonatal data were obtained from the delivery records. Obstetric factors for the development of OASR were assessed with multivariate logistic regression analysis.

No significant association was found between the primiparous age category and OASR. Vacuum extraction, forceps delivery, and the head circumference of the neonate were found to be independent risk factors for OASR, while the use of mediolateral episiotomy or epidural analgesia were independent protective factors for developing OASR.

Primiparous women, 35 years of age or older, do not seem to have a greater risk of OASR than younger primiparous women. Risk factors for OASR are instrumental vaginal delivery and the size of the neonate. Mediolateral episiotomy and epidural analgesia seem to reduce the risk for OASR.