Will I tear…again? Delivery after anal sphincter injury

By Eva Martin, MD of Elm Tree Medical Inc.

“Will I tear?” One of the most common but avoided topics in labor and delivery is tearing, or lacerations, during vaginal birth. As I’ve reported in the past (for Pregnancy & Newborn Magazine!), 90% of first-time moms and 70% of veteran mothers do have a tear during birth. The vast majority of these tears are easily repaired by an experienced provider and don’t have any long-term side effects after recovery. However, a small percentage, 2.5%, of mothers will have a more serious tear. For these mothers, what happens if they get pregnant again? Should they avoid vaginal delivery altogether just in case? Will the way they deliver their next baby influence whether they have incontinence in the future?

A group of researchers from Herlev University in Denmark wanted to answer this very question. They collected questionnaires from 1,978 women who had suffered a serious vaginal tear during their first delivery. Called “third-degree” or “fourth-degree” lacerations, these types of tears involve the anal sphincter. The anal sphincter is a small muscle that helps to control defecation. Women with a history of injury to this important muscle are at higher risk of having anal incontinence as they age.

The almost 2,000 women participating in the research study had experienced an anal sphincter injury during their first delivery and had delivered a second child sometime after that injury. 1,472 or 72% of the women had a vaginal delivery with their second child, and 506 or 25% of the women had an elective cesarean delivery (did not labor). In theory, you might assume that having an elective c-section is the safer option since it guarantees no repeat injury to the vaginal or anal areas during the birth. Did the women who had a vaginal delivery suffer more incontinence than those who had elective cesarean deliveries?

The data is a little complicated to decipher because the two groups were pretty different after the first delivery. As you might guess, women with worse outcomes after the first delivery were more likely to elect to have a cesarean delivery for their second. Following the first delivery, 29% of women who went on to have a second vaginal delivery had anal incontinence, and 56% of women who went on to have an elective cesarean section had anal incontinence. After a vaginal delivery, the number of women experiencing long-term anal incontinence went up to 39%. After an elective cesarean section, the number of women experiencing long-term anal incontinence was about the same as before the second delivery- 53%. This is a bit confusing, so the researchers created a statistical model to see how important type of delivery was in predicting long-term anal incontinence. They found that it was not a significant predictor in whether a woman suffered from long-term anal incontinence. What did predict long-term incontinence? Whether or not a patient had persistent anal incontinence after the first delivery. Nevertheless, patients with a second vaginal delivery had a higher risk of deterioration.

The results are therefore nuanced. While type of delivery doesn’t determine the risk of long-term anal incontinence, there were more women with a second vaginal delivery who had a deterioration of symptoms. The end result? Do what is best for you. Talk to your doctor or midwife, discuss your concerns and hopes for your delivery and the future. If this study shows us anything, it’s that both options are reasonable.