Perineal massage during pregnancy and during delivery can reduce tearing and the need for an episiotomy (a surgical incision to enlarge the vaginal opening during childbirth). The effect seems greatest for a first delivery.
Perineal massage is the practice of inserting one or two lubricated fingers about two inches into the vagina and applying pressure on the pelvic muscles and tissues for 10 minutes once or twice a week starting at 34 — 35 weeks of pregnancy. The massage can be done by the pregnant person or her partner.
For a first pregnancy, perineal massage has a modest and definitely measurable impact on reducing the need for stitches (either from tearing or an episiotomy). This translates to reducing the need for stitches by approximately 10 percent and the need for episiotomy by approximately 15 percent. In subsequent pregnancies there does not appear to be an effect of perineal massage on tearing or episiotomies, but there may be a reduction in pain after delivery.
Once you are in labour and are fully dilated perineal massage and warm compresses appear to reduce the severity of the tear, but not the overall risk of experiencing tearing or needing an episiotomy.
Reducing the severity of tearing during a delivery is an important goal. Women who have larger tears that affect the anal sphincter (muscles that control continence of gas and stool) can suffer greatly often for years after giving birth. So while statistically speaking the absolute reduction in tears and the need for an episiotomy from perineal massage both before and during delivery may not seem large, all efforts to reduce anal sphincter tears are important and valuable.
The New York Times