Episiotomy use among vaginal deliveries and the association with anal sphincter injury: a population-based retrospective cohort study

To The Editor:

We thank Drs. Klein and Kaczorowski (1) for their interest in our article (2). Although we found some of their arguments distracting and dated, we welcome this opportunity to clarify our position.

Klein and Kaczorowski are correct in pointing out that our analysis focused on hospital deliveries, which included approximately 98% of all deliveries in Canada (excluding Quebec) (3). We characterized trends in episiotomy use in Canada and are unaware of data sources that contains such information for home births. Comparing differences in rates of episiotomy, operative vaginal delivery (OVD), and obstetric anal sphincter injury (OASI) in our study with those in the study by Janssen et al. (4) is not particularly meaningful as the latter was restricted to low risk women. Additionally, the Janssen et al. study included deliveries from 15 to 20 years ago when OASI rates were significantly lower (5).

Klein and Kaczorowski appear to have missed the main conclusion of our study which showed a) that episiotomy use in Canada has declined among both spontaneous vaginal deliveries and among operative vaginal deliveries (OVD) and b) that episiotomy use in spontaneous vaginal deliveries increases the risk of OASI, while episiotomy use in operative vaginal deliveries protects against OASI. The former finding, namely, that episiotomy increases OASI risk in spontaneous vaginal deliveries, has been documented in several randomized trials (6) and is not under debate: the SOGC guideline (7) on the use of episiotomy in spontaneous vaginal delivery already reflects the evidence. However, both the 2017 Cochrane review (6) on routine vs selective episiotomy use and the World Health Organisation’s (8) 2018 guideline on intrapartum care emphasize that the role of episiotomy among OVD remains to be established. It is on this latter issue that our study provides important evidence. The fact that forceps deliveries comprised 2.9% of deliveries (not 2.3% as stated) among nulliparous women and women with a vaginal birth after cesarean (VBAC) delivery is entirely irrelevant as the above-mentioned associations were evaluated among 66,503 forceps deliveries.

The randomized trial of episiotomy use in North America by Klein et al. (9) contributed to reducing unnecessary pain and OASI rates among women with spontaneous vaginal deliveries. However, this trial did not provide any insight into the relationship between episiotomy use and OASI among OVDs as it included a total of 20 forceps deliveries, and was carried out 30 years ago when median episiotomy was common practice. Similarly, reference to the study by Ecker et al. (10) is not helpful partly because it was based on a crude analysis of 2,041 deliveries occurring at single institution between 1984 and 1994. Further, the study documented a sharp reduction in episiotomy rates among OVDs to nulliparous women from 96.5% in 1984 to 38.7% in 1994, and a concurrent striking reduction in 4th degree perineal laceration rates from 14.8% in 1984 to 5.8% in 1994 (rates of 3rd degree tears were 28.3% and 29.7% in 1984 and 1994, respectively). The temporal reduction in 4th degrees perineal tears notwithstanding, these stratospheric rates of 3rd and 4th degree perineal laceration have little bearing on present day discourse in Canada where the same rates in 2004-2017 were substantially lower (rate of 3rd degree tears 13.3% to 14.6% and rate of 4th degree tears 2.1% to 2.2% following OVD among nulliparous women (2)).

We carried out additional analyses by the main maternity care provider responsible for the care during the delivery hospitalization (irrespective of who conducted the delivery) but the results did not alter the interpretation of our study results. Multivariable regression analyses among nulliparous women showed no significant differences in the association between episiotomy use and OASI by provider type except among women delivering by vacuum (rate ratio [RR] 1.22, 95% confidence interval [CI] 1.02-1.48 for midwives; RR 0.88, 95% CI 0.84-0.92 for obstetricians; and RR 0.89, 95% CI 0.83-0.96 for general practitioners [GPs]). Among parous women without a previous cesarean delivery the association between episiotomy and OASI among spontaneous vaginal deliveries was significantly stronger among women with midwives as the main service provider (RR 4.42, 95% CI 3.28-5.95; RR 2.58, 95% CI 2.40-2.77; and RR 2.66, 95% CI 2.33-3.03 for deliveries with midwives, obstetricians and GPs, respectively). Among women with a VBAC delivery, the protective association between episiotomy use and OASI among forceps deliveries was significantly different by provider type (RR 0.22, 95% CI 0.08-0.59; RR 0.88, 95% CI 0.69-1.12; and RR 1.17, 95% CI 0.76-1.81 for deliveries with midwives, obstetricians and GPs as the main service provider, respectively). This was also true among vaginally nulliparous women who had a vaginal birth following a cesarean delivery.

References

1. Klein MC, Kaczorowski J. Encouraging routine use of episiotomy with forceps questioned.
2. Muraca GM, Liu S, Sabr Y, et al. Episiotomy use among vaginal deliveries and the association with anal sphincter injury: a population-based retrospective cohort study. CMAJ 2019;191:E1149-58.
3. Statistics Canada. Live births and fetal deaths (stillbirths), by place of birth (hospital or non-hospital). Accessed from https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310042901 on 15-Dec-2019.
4. Janssen PA, Saxell L, Page LA, et al. Outcomes of planned home birth with registered midwife versus planned hospital birth with midwife or physician. CMAJ 2009;181377-383.
5. Muraca GM, Lisonkova S, Skoll A, et al. Ecological associations between operative vaginal delivery and obstetric and birth trauma. CMAJ 2018;190:E734-41.
6. Jiang H, Qian X, Carroli G, et al. Selective versus routine use of episiotomy for vaginal birth. Cochrane Database Syst Rev. 2017 Feb 8;2:CD000081.
7. Lee L, Dy J, Azzam H. Management of spontaneous labour at term in healthy women. J Obstet Gynaecol Can, 2017; 38: 843-65.
8. World Health Organisation. Intrapartum care for a positive childbirth experience. Geneva: World Health Organization. 2018.
9. Klein MC, Gauthier RJ, Jorgensen SH, et al. Does episiotomy prevent perineal trauma and pelvic floor relaxation?. Online Journal of Current Clinical Trials 1992;Doc 10:0‐29. Accessed Dec 15, 2019.
10. Ecker JL, Tan WM, Bansal RJ, et al. Is there a benefit to episiotomy at operative vaginal delivery? Observations over ten years in a stable population. Am J Obstet Gynecol 1997:176:411-4.