European Journal of Obstetrics & Gynecology and Reproductive Biology 185 (2015) 9–12
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OASI: a preventable injury? Habiba Kapaya, Sharifah Hashim, Swati Jha * Department of Urogynaecology, Level 4 Jessop Wing, Shefﬁeld Teaching Hospitals, NHS Trust, Tree Root Walk, Shefﬁeld S10 2SF, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history: Received 4 August 2014 Received in revised form 7 November 2014 Accepted 17 November 2014
Objective: The aim of this study was to determine risk factors for obstetric anal sphincter injury and whether any of them were modiﬁable. Study design: This was a retrospective review of 2572 women (cases = 1286; controls = 1286) that took place over a 10 year period at a University teaching hospital. Maternal (Age, Parity, BMI and ethnicity), Obstetric (gestational age, assistance during delivery, episiotomy) and fetal (weight) risk factors were analyzed using logistic regression model presented as odds ratio (OR) with 95% conﬁdence intervals (CI). Both univariate and multivariate analyses were conducted with outcome variables comparing cases and controls. Cases without instrumental deliveries were also compared to controls to exclude for the effect of assisted delivery. Results: This study shows that in addition to instrumental delivery, primiparity (OR 9.8; CI 7.8–12.3), episiotomy (OR 8.6; CI 6.4–11.6), gestational age over 41 weeks (OR 1.5; CI 1.2–1.9), fetal weight over 4 kg (OR 3.2; CI 2.3–4.4) and Asian ethnicity (OR 1.9; CI 1.4–2.7) were all strongly associated with OASI. A raised BMI over 30 appeared to have a protective effect (OR 0.4; CI 0.2–0.5). Conclusions: Most risk factors related to OASI are non-modiﬁable however gestational age and episiotomy are modiﬁable risk factors. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: OASI Risk factors Episiotomy Instrumental delivery
Introduction OASI (obstetric anal sphincter injuries) which include third (3a, b and c) and fourth degree tears complicate 0.5–1.5% of vaginal deliveries  and are associated with signiﬁcant morbidity. About 30–50% of these women suffer from chronic anal incontinence, dyspareunia, fecal urgency or perineal pain [2,3]. The seriousness of the complications after OASI is related to the severity of sphincter injury. There is no consensus regarding preventive measures and clinical management of severe perineal tears. There are also conﬂicting data regarding the signiﬁcance of various obstetric risk factors for such tears. Several studies have identiﬁed a number of obstetric risk factors associated with sphincter injury. Factors consistently shown to be associated with perineal tears are instrumental delivery, with forceps associated with a higher risk than ventouse, longer duration of second stage of labor, nulliparity, birth weight and occipito posterior position [1,4,5]. However, many of the studies in the literature are contradictory on other factors such as episiotomy and ethnicity . Establishment of risk factors for such tears may enable earlier identiﬁcation of patients at risk and the use of preventive measures.
* Corresponding author. Tel.: +0044 0 114 2268166; fax: +0044 0 121 6272102. E-mail addresses: [email protected]
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(S. Jha). http://dx.doi.org/10.1016/j.ejogrb.2014.11.023 0301-2115/ß 2014 Elsevier Ireland Ltd. All rights reserved.
The aim of this study was to determine possible risk factors for third and fourth degree perineal tears in a single universityafﬁliated maternity hospital with approximately 8000 deliveries per year and strategies for prevention.
Materials and methods This is a retrospective case-control study over a ten-year period from January 1st 2003 to December 31st 2012. The study was performed at the Jessop Wing Hospital, Shefﬁeld Teaching Hospitals a tertiary-referral University hospital where approximately 8000 deliveries take place annually. The incidence of OASI in this unit is 3% but ﬂuctuates between 1 and 5% which is within national averages. The study population comprised 2572 women (cases = 1286; controls = 1286), who met the following inclusion criteria: singleton pregnancy, vertex presentation, and vaginal delivery. Multifetal pregnancies, breech presentations, and caesarean sections were excluded from the analysis. Case records of all women who sustained an OASI were identiﬁed from the maternity record database and examined for the presence of risk factors. Women without anal sphincter injury, matched for maternal age with each case was identiﬁed from the maternity database as a control. The control group did not have an instrumental delivery as this is a known risk factor for OASI .
H. Kapaya et al. / European Journal of Obstetrics & Gynecology and Reproductive Biology 185 (2015) 9–12
OASI was assessed and classiﬁed clinically using the accepted Standardised classiﬁcation system of the Royal College of Obstetricians and Gynaecologists (RCOG). Though, anal endosonography is more accurate and provides more information on the extent of OASI compared to clinical and conventional physiological methods , it is not routine practice to perform scans to conﬁrm diagnosis and current RCOG recommendations are that this should be a clinical diagnosis (RCOG, Green Top Guideline no 29; 2007). In this study, no distinction was made between the third and fourth degree perineal tears for the analysis of data. The following data on maternal characteristics were collected: age, parity, body mass index (BMI) and ethnicity. Ethnicity was categorized as White Caucasians, Asian, Black and mixed origins. Parity was classiﬁed into two categories: women delivering their ﬁrst child (‘‘primiparous’’) and women with a history of one or more vaginal deliveries (‘‘multiparous’’). BMI was divided into 3 categories: 35). Obstetric data collected were: induction of labor, episiotomy performed, gestational age at the time of delivery >41 weeks which had an afﬁrmative or negative response (yes/no) and the type of instrumental deliveries (forceps or vacuum). The infant variables identiﬁed were gestational age at the time of delivery and birth weight (kg). The relationship between potential maternal, obstetric and infant related risk factors for OASI were analyzed using logistic regression model presented as odds ratio (OR) with 95% conﬁdence intervals (CI). This study was conducted as a service evaluation project so formal ethical approval was not required. Both univariate and multivariate analyses were conducted with the outcome variables comparing cases and controls. Women who sustained an OASI without an instrumental delivery were also compared to controls by conducting multivariate analysis to exclude for the effect of instrumental delivery. These analyses were done, using SPSS version 21. The level of signiﬁcance was set at P < 0.05. Results One thousand two hundred and eighty six women with OASI and the same number of age matched controls were identiﬁed during the study period. The controls were of similar age (29.5 5.8 vs 28.5 5.6), BMI (25.9 19.3 vs 26.6 6.5) and ethnicity. Descriptive statistics for the subjects and birth are shown in Table 1. Cases and control subjects differed signiﬁcantly on most predictor variables. Cases were more likely to be nulliparous (59.6% vs 11%), delivered heavier infants at mean gestational age
Table 2 Univariate analysis for risk factors in women with and without OASI. Odds ratio [95% conﬁdence interval]
Age (reference = 20–40) 40 yrs Parity (reference = multiparous) Primiparous Ethnicity (reference = white) Asian Black Mixed BMI (kg/m2) Reference 30 Between 30 and 35 >35 Gestational age (reference 41 weeks) >41 weeks Labor (reference =spontaneous) Induction Episiotomy (reference = no) Yes Birth weight Reference 4 kg >4 kg
Overall P value