Obstetric Anal Sphincter Injuries (OASIS): Pelvic floor physiotherapy can help!

By Tiffaney Marlow, Reg. PT

Pelvic floors are incredibly adaptive and undergo vast changes during pregnancy and delivery. The muscles and fascia work to support the pelvic girdle while your body changes over 9 months. It then has an incredible capacity to stretch and accommodate for your baby throughout the delivery process. Despite this great capacity for change these  tissues are still susceptible to injury, whether spontaneously as a tear or secondary to a controlled episiotomy at your attending health care professional’s discretion. This injury most commonly occurs at what we call the perineum.

The perineum is the space between the vaginal opening and the rectum where many of the deep and superficial muscles of the pelvic floor converge on a central tendon. The perineum plays a key role in maintaining the stability of the pelvic floor musculature and when damaged can lead to a number of complications including but not limited to painful sex, urinary or fecal urgency and incontinence (the loss of control of your bladder or bowels).

Perineal tears are graded based on their severity

Grade I – the entrance of the vagina and superficial skin of the perineum

Grade II – beyond the entrance of the vagina, including the muscle and fascia of the perineum

Grade III – entrance of the vagina, muscles and fascia of the perineum and the anal sphincter

3a – partial tear of the external sphincter (<50% thickness)

3b – >50% of the external anal sphincter

3c – internal sphincter is torn

Grade IV – entrance of the vagina, perineum, anal sphincter (external and internal) and stretching into the rectum

Grade III and IV tears are also known as Obstetrical Anal Sphincter Injuries or OASIS and occur in 4-6.6% of vaginal deliveries. These injuries are linked to postpartum pain, urinary retention and fecal incontinence if not caught early and repaired.

The Society of Obstetricians and Gynecologists of Canada’s recent guideline on Obstetrical Anal Sphincter Injuries recommends that there are interventions that can be performed to hep reduce OASIS including:

– slowing the head of the infant during the delivery of the head reduces OASIS by 50-70%

– applying perineal pressure and massage during delivery may reduce OASIS

– sitting and kneeling positions for delivery with support of the sit bones is best to reduce pressure on the perineum would be preferred

– if instruments are required during delivery then a vacuum is preferred to forceps to reduce OASIS

If an anal sphincter injury does occur the evidence is clear that women with anal incontinence should be referred to pelvic floor physiotherapy (J Obstet Gynaecol Can 2015;37 (12):1131-1148). A pelvic physiotherapist specializes in retraining the damaged muscles of the pelvic floor, they help manage pain associated with scarring and can facilitate retraining of the sphincters to help regain continence postpartum. If you are having difficulty with pelvic pain, urgency or incontinence postpartum be sure to speak with one of our pelvic floor physiotherapists!