Episiotomy rates dropped dramatically. Laceration rates? Not so much.

“Natural” childbirth advocates have presented episiotomies as exhibit A in their case against modern obstetrics. They argued for years that episiotomies are unnecessary, or even harmful. Research done in the 1990s seemed to confirm their view by showing a correlation between episiotomies and third and fourth degree perineal lacerations. Third degree lacerations involve disruption of the anal sphincter and fourth degree lacerations extend into the tissue of the rectum itself. Both types of lacerations can have long term consequences including bowel incontinence and recto-vaginal fistula.

Based on the correlation of episiotomies and severe lacerations, obstetrics made an about face on episiotomies. Episiotomies are now discouraged, except in specific instances. The assumption was that a decline in episiotomy rates would lead to a decline in rates of serious perineal lacerations. That has not happened.

Episiotomy in the United States: has anything changed? by Frankman et. al reviews trends in episiotomy and severe lacerations over 25 years, from 1979-2004. Although the episiotomy rate has declined dramatically, the rate of third and fourth degree lacerations has remained unchanged.

Rate of episiotomy with all vaginal deliveries decreased from 60.9% in 1979 to 24.5% in 2004…

With the use of linear regression, the rate of episiotomy with vaginal delivery
decreased by 1.4% per year from an intercept rate in 1979 of 60.9% between 1979 and 2004…

Overall AARs [age adjusted rates] of anal sphincter laceration did not change between 1979 and 2004 (4.5-5.0%).

The authors broke down the statistic into episiotomies associated with spontaneous vaginal delivery and episiotomies associated with operative vaginal delivery (forceps or vacuum).

… Episiotomy with spontaneous vaginal delivery decreased, whereas episiotomy with operative vaginal delivery remained high. Episiotomy with forceps-assisted vaginal delivery declined (83.2% in 1979 to 11.7% in 2004), whereas episiotomy with vacuum-assisted vaginal delivery increased (0.7% in 1979 to 38.1% in 2004). These changes were associated with a shift in obstetric practices favoring vacuum-assisted over forceps-assisted vaginal delivery. The overall rate of forceps-assisted vaginal delivery decreased from 8.2 per 1000 women in 1979 to 0.8 per 1000 women in 2004. The rate of vacuum-assisted vaginal deliveries increased from 0.1 per 1000 women in 1979 to 3.7 per 1000 women in 2004.

… When episiotomy with spontaneous vaginal delivery was analyzed separately, episiotomy rates decreased by 1.4% per year from a rate of 53.4% in 1979 over
the study interval. Similarly, an analysis of episiotomy rates with operative vaginal
delivery demonstrated an annual increase of 1.2% from a rate in 1979 of 84.0% between 1979 and 2004.

… When the AAR of anal sphincter laceration was evaluated by vaginal delivery type, the rates were highest among women undergoing operative vaginal delivery. The AAR for anal sphincter laceration for operative vaginal delivery increased from 7.7% in 1979 to 20.5% in 1996, followed by a decrease to 15.3% in 2004. For spontaneous vaginal delivery, the rate of anal sphincter laceration increased from 5% in 1979 to
a peak of 8.9% in 1987 and then steadily decreased to 3.5% in 2004.

In other words, for spontaneous vaginal delivery as the episiotomy rate declined by 63%, the rate of severe lacerations declined by only 30%. For operative vaginal delivery, as the rate of episiotomy declined by 40%, the rate of severe lacerations increased by 100%.

The graph below illustrates these trends. It was adapted from the paper. It shows rates of episiotomy by delivery type (solid lines) and rates of severe lacerations by delivery type (dotted lines).

The authors, staunch opponents of episiotomy insist:

Decreasing rates of episiotomy have corresponded with decreasing age-adjusted rates of anal sphincter laceration. However, rates of episiotomy and anal sphincter laceration remain high for operative vaginal delivery (50.1% and 15.3% in 2004, respectively). Episiotomy and operative vaginal delivery are well known risk factors for anal sphincter laceration.The high rates of anal sphincter laceration associated with forceps- and vacuum-assisted vaginal delivery are probably the direct result of continued use of episiotomy with these procedures

That’s not how I read the graph. The steep decline in episiotomy rates for spontaneous vaginal delivery resulted in a much more modest decline in severe lacerations. The steep decline in episiotomy rates for operative vaginal delivery resulted in an increase in severe lacerations.

The evidence does not indicate that episiotomy is associated with the persistently high rate of severe lacerations in operative vaginal deliveries. It indicates that the rate of severe lacerations seems to be independent of the episiotomy rate. In the case of spontaneous vaginal delivery, the decrease in episiotomy does not lead to a decrease of comparable magnitude in severe lacerations.

These findings suggest that there are other factors involved in the rate of severe lacerations besides episiotomy. It’s not argument for brinding back routine use of episiotomy, but it does suggest that the “dangers” of episiotomy have been exaggerated.