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.

A Mahmood, vice president,4 Allan Templeton, professor of obstetrics and gynaecology, 4 Jan H van der Meulen, professor of clinical epidemiology 1,4 ABSTRACT Objective To determine whether the variation in unadjusted rates of caesarean section derived from routine data in NHS trusts in England can be explained by maternal characteristics and clinical risk factors. Design A cross sectional analysis using routinely collected hospital episode statistics was performed. A multiple logistic regression model was used to estimate the likelihood of women having a caesarean section given their maternal characteristics (age, ethnicity, parity, socioeconomic deprivation) and clinical risk factors (previous caesarean section, breech presentation, fetal distress). Adjusted rates of caesarean section for each NHS trust were produced from this model. Setting 146 English NHS trusts. Population Women aged between 15 and 44 years with a singleton birth between 1 January and 31 December 2008. Main outcome measure Rate of caesarean sections per 100 births (live or stillborn). Results Among 620 604 singleton births, 147 726 (23.8%) were delivered by caesarean section. Women were more likely to have a caesarean section if they had had one previously (70.8%) or had a baby with breech presentation (89.8%). Unadjusted rates of caesarean section among the NHS trusts ranged from 13.6% to 31.9%. Trusts differed in their patient populations, but adjusted rates still ranged from 14.9% to 32.1%. Rates of emergency caesarean section varied between trusts more than rates of elective caesarean section. Conclusion Characteristics of women delivering at NHS trusts differ, and comparing unadjusted rates of caesarean section should be avoided. Adjusted rates of caesarean section still vary considerably and attempts to reduce this variation should examine issues linked to emergency caesarean section. INTRODUCTIONSince the 1970s, many developed countries have experienced substantial growth in the rates of caesarean section.1-3 In England, for example, the rate of caesarean sections has increased from 9% in 1980 to 24.6%

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