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 E ngland 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 E nglish N ational H ealth S ervice between 1 A pril 2000 and 31 M arch 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.