Third‐ and fourth‐degree perineal tears among primiparous women in England between 2000 and 2012: time trends and risk factors

Abstract

Objective To describe the trends of severe perineal tears in England and to investigate to what extent the changes in related risk factors could explain the observed trends.Design A retrospective cohort study of singleton deliveries from a national administrative database.Setting The English National Health Service between 1 April 2000 and 31 March 2012.Population A cohort of 1 035 253 primiparous women who had a singleton, term, cephalic, vaginal birth.Methods Multivariable logistic regression was used to estimate the impact of financial year of birth (labelled by starting year), adjusting for major risk factors.Main outcome measure The rate of third-degree (anal sphincter is torn) or fourth-degree (anal sphincter as well as rectal mucosa are torn) perineal tears.Results The rate of reported third-or fourth-degree perineal tears tripled from 1.8 to 5.9% during the study period. The rate of episiotomy varied between 30 and 36%. An increasing proportion of ventouse deliveries (from 67.8 to 78.6%) and non-instrumental deliveries (from 15.1 to 19.1%) were assisted by an episiotomy. A higher risk of third-or fourth-degree perineal tears was associated with a maternal age above 25 years, instrumental delivery (forceps and ventouse), especially without episiotomy, Asian ethnicity, a more affluent socio-economic status, higher birthweight, and shoulder dystocia.Conclusions Changes in major risk factors are unlikely explanations for the observed increase in the rate of third-or fourth-degree tears. The improved recognition of tears following the implementation of a standardised classification of perineal tears is the most likely explanation.Keywords Episiotomy, instrumental delivery, severe perineal trauma, trends, vaginal delivery.

Risk and protective factors for obstetric anal sphincter injuries: A retrospective nationwide study

“…The number needed to treat to prevent one obstetric anal sphincter injury during vacuum‐assisted delivery was found to be 50. This finding is supported by previous studies, which reported a decrease in obstetric anal sphincter injuries when episiotomy was used in operative vaginal deliveries 8, 25, 28, 29. Jangö et al report a number needed to treat of 23 mediolateral episiotomies and Raisänen et al report a number needed to treat of 66 lateral episiotomies to prevent one case of obstetric anal sphincter injury in vacuum‐assisted deliveries, thus favoring more frequent use of episiotomy in such cases 28, 30.…”

“…As supported by the literature, we found operative vaginal delivery7, 8, 13, 14, 15 to be an independent risk factor for sphincter damage. In particular, forceps delivery has consistently been shown to represent one of the major risk factors for obstetric anal sphincter injuries 16, 17, 18, 19.…”

“…Episiotomy has previously been found to increase the risk for obstetric anal sphincter injuries 8, 20. However, looking at episiotomy as a single variable is insufficient and therefore we additionally analyzed the use of mediolateral episiotomy according to birth mode.…”

“…Furthermore, risk factors such as episiotomy, epidural analgesia, induction of labor, and advanced maternal age have also been associated with obstetric anal sphincter injuries, but not consistently 6, 7. Several population‐based studies have reported a gradual increase in obstetric anal sphincter injuries in the last decades with an incidence ranging from 4.1% to 16.0% 7, 8, 9. The exact reason for this increase remains unclear.…”

“…The exact reason for this increase remains unclear. Changes in demographic risk factors such as the rise in maternal age, higher fetal birthweight, improvement of diagnostic attention, and better documentation through national birth registries explain only part of the substantial increase in obstetric anal sphincter injuries 8. Interestingly, in some countries, the use of forceps at delivery, although one of the major risk factors, has risen in the past years and may have contributed to this trend 8, 10…”