News for Your Practice

Anal sphincter injury at childbirth

Author and Disclosure Information

Immediate or delayed repair? Overlapping or end-to-end technique? Midline or mediolateral episiotomy? Plus: risk factors, and tactics for subsequent deliveries.



There is a crisis of confidence in vaginal delivery. Women are aware of the potential for devastating consequences, and many ask for elective cesarean solely to avoid any possibility of incontinence or other problems linked to vaginal delivery.

Many obstetricians also have misgivings, though they are well aware that a cesarean is far more likely to cause maternal morbidity.1 In a survey of female obstetricians, 31% chose elective cesarean as their preferred mode of delivery—80% of whom gave fear of perineal trauma as their reason.2

We cannot dispute the risks. The incidence of anal incontinence following recognized obstetric anal sphincter injury (OASI) is estimated at over 60%,3 and the true incidence may be much higher,4 particularly when injury goes unrecognized at the time of delivery.

OASI—any 3rd- or 4th-degree perineal tear—causes far more morbidity than episiotomy alone or 1st- or 2nd-degree tears ( FIGURE 1). It is the most common cause of postpartum anal incontinence. Anal incontinence is defined by the International Continence Society as involuntary loss of flatus or feces that becomes a social or hygienic problem.5 What’s more, incontinence due to OASI causes very high cumulative health service costs.13

Lack of uniform classification, insufficient training, and limited evidence from randomized controlled trials all contribute to the notoriously poor outcomes of obstetric anal sphincter injury.

To improve the outcome and reestablish confidence in vaginal delivery, more training is needed, as is more research directed toward identifying how to prevent, identify, and manage anal sphincter injury following vaginal delivery.

Taboos, embarrassment, and mistaken thinking

Even though anal incontinence may be both physically and psychologically devastating, many women do not seek medical attention due to embarrassment.6-10 One study, for instance, found that only a third of women with fecal incontinence had ever discussed the problem with a physician.11

Wood et al10 reported that most women with anal sphincter injury were either unaware that they had the injury, or felt they did not receive an adequate explanation of their injury.

Some women chose not to speak with their doctors because they believed that anal incontinence was a normal consequence of childbirth.6,12

The scope of life-disrupting morbidities

Perineal pain and dyspareunia may persist for years

Perineal pain can be so distressing for the new mother that it may interfere with her ability to breast feed and cope with the daily tasks of motherhood.14 Short-term perineal pain is associated with reactionary edema, bruising, tight sutures, infection, and wound dehiscence. Persistent pain and discomfort from perineal trauma may also cause urinary retention and defecation problems.

Perineal pain and dyspareunia, which greatly impair sexual and social life, may last for many years after childbirth.6,15-17 Wheeless,18 for instance, reported that some women refrained from sexual intercourse for up to 14 years because of dyspareunia following sphincter injury.

Abscess formation, wound breakdown, rectovaginal fistulae

Following primary repair of OASI, Venkatesh et al19 noted a 10% wound disruption rate.

Price of missed injury could be colostomy. Most rectovaginal fistulae occur when the physician fails to recognize the true extent of sphincter injury at the time of repair, resulting in inadequate sphincter reconstruction and wound breakdown.17 Once rectovaginal fistulae have occurred, treatment is difficult and may ultimately require permanent colostomy.17,20

6 Risk factors for perineal trauma

1. Nulliparity

Because nulliparous women have a relatively inelastic perineum,21 time for perineal stretching during the second stage of labor is often inadequate, and perineal trauma is therefore more likely. Further, compared to the multipara, nulliparous women undergo more episiotomies to prevent perineal trauma, and are more likely to have instrumental delivery. This combination of factors increases their risk of OASI.

2. Macrosomia

Birth weight of more than 4 kg imposes risk of perineal injury, especially 3rd- and 4th-degree tears,8,22,23 due to larger head circumference, prolonged labor, and difficult delivery, especially if instrumental delivery is used. Even after safe delivery of the head, shoulder dystocia—more common in macrosomic infants—may contribute to perineal and anal sphincter trauma. A large baby is also likely to disrupt the fascial supports of the pelvic floor and cause a stretch injury to the pelvic and pudendal nerves.


Next Article: