A study from the United States has shown that perineal laceration occurring in two or more vaginal deliveries poses a significant risk of future pelvic floor problems.

A cohort of 449 women, with at least one vaginal delivery, was followed up for an average of 7.5 years. Method of delivery (spontaneous, forceps or vacuum) was recorded. Subsequent pelvic floor disorders (urinary dysfunction, anal incontinence and pelvic organ prolapse) were assessed using a validated questionnaire. A gynaecological examination was also carried out to assess pelvic organ support.

Episiotomy and laceration rates were not related to variations in ethnicity, maternal obesity or fetal macrosomia. Spontaneous perineal laceration was significantly related to being multiparous and less than 35 years old at the time of birth of the first child.

Just 3% of all deliveries were without laceration or episiotomy. There was a history of both laceration and episiotomy in 94 women (21%). The same percentage had anal sphincter laceration.

Overall, 57% of women experienced perineal laceration, 20% with more than one delivery; 61% of women had episiotomy and 15% more than one.

At follow up 5-10 years after delivery, stress incontinence was present in 71 women (16%). Overactive bladder, anal incontinence and symptomatic prolapse and signs of prolapse were noted in 45 (10%), 56 (12%), 19 (4%) and 64 (14%) respectively.

Having a forceps delivery was associated with a three-fold higher incidence of overactive bladder, odds ratio (OR) 2.92 (95% CI: 1.44-5.93) and double the incidence of demonstrable prolapse, OR 1.95 (95% CI: 1.03-3.70). The authors calculated that one extra case of prolapse occurred for every eight forceps-assisted deliveries.

Women with a history of more than one perineal laceration were significantly more likely to have prolapse to, or beyond, the hymen, OR 2.34 (95% CI: 1.13 -4.86). Multiple episodes of perineal laceration doubled the incidence of demonstrable prolapse (24% vs 12%).

Neither episiotomy nor vacuum extraction was significantly associated with the development of any pelvic floor disorder. Anal incontinence was not significantly related to any of the modes of delivery or birth trauma.

Vaginal laceration during birth is a natural consequence of our need as humans to be born with a relatively large brain and head. Research suggests that by the time the vaginal wall and perineum start to tear during delivery, the attachment of the levator ani muscles to the pubic bone may have already been disrupted. This hidden trauma is related to later uterovaginal prolapse and urinary dysfunction.

Timely episiotomy, rather than spontaneous laceration, seems to be a safety valve against pelvic floor damage.

Dr Chris Barclay

• Handa VL, Blomquist JL, McDermott KC et al. Pelvic floor disorders after vaginal birth. Effect of episiotomy, perineal laceration, and operative birth. Obstet Gynecol 2012;119:233-9