Risk Factors For Obstetric Anal Sphincter Injuries Research Articles

Predicting obstetric anal sphincter injuries among laboring women: 2 prediction models and 1 risk calculator

Abstract Background: Although several prediction models have been developed to estimate the risk of obstetric anal sphincter injuries (OASIS) among laboring women, none have been used in clinical practice because of controversial or unavailable predictors included in the prediction models and the format used to present them. Thus, it is essential to develop evidence-based prediction models for OASIS using known antenatal and modifiable intrapartum factors and to present them in user-friendly formats. Objective: The objective of this study was to develop evidence-based prediction models for OASIS and a risk calculator to present prediction models. Methods: Models were developed based on a systematic review and meta-analysis in which risk factors for OASIS were identified, and the pooled odds ratio for each risk factor was calculated. A logistic regression model was used to develop the prediction models, and MATLAB with a graphical user interface was used to develop the risk calculator. Results: Two prediction models for OASIS were established: Model I and Model II. Model I included 7 known antenatal variables: maternal age, parity, prior cesarean delivery, prepregnancy body mass index, gestational age, estimated birth weight, and fetal position. Model II added 5 modifiable intrapartum variables to Model I: epidural analgesia, labor induction, labor augmentation, episiotomy, and operative vaginal birth. The risk calculator developed by writing the parameters in the logistic regression models into MATLAB scripts included 2 interfaces, each consisting of risk factors for OASIS and the possibility of OASIS occurring. Conclusions: This study developed 2 prediction models and a risk calculator for OASIS based on a systematic review and meta-analysis. Although the models were more scientific in model development methods and predictors included in the prediction models, they should be externally validated and updated to ensure better performance before they can be widely applied to guide clinical practice.

A Retrospective Cross-Sectional Study on the Association Between Newborn’s Head Circumference at Birth and Obstetric Anal Sphincter Injuries among Primigravidae

Introduction: Obstetric anal sphincter injuries (OASIS) is a term used to describe third- and fourth- degree perineal trauma during childbirth. There are a lot of risk factors associated with OASIS, however newborn’s head circumference (HC) at birth as a risk factor is understudied. The aim of this study was to determine the incidence of OASIS and establish the association between newborn’s HC at birth and OASIS among primigravidae who delivered in Hospital Raja Permaisuri Bainun (HRPB) from 2016 to 2018. Other OASIS risk factors were also analysed. Methods: This was a retrospective cross-sectional study among primigravidae who delivered in HRPB from 2016 till 2018. Systematic sampling method was used, and the total sample recruited was 538. Women who sustained OASIS were compared to women without OASIS. Simple and multiple logistic regression analysis were used to look for the association between associated risk factors and OASIS. Results: The incidence of OASIS in HRPB during the study period was 2.0%. Newborn’s HC at birth (p=0.588) was not significantly associated with OASIS, whereas birth weight (OR 1.002 95%CI 1.001-1.004 p=0.06) and instrumental delivery (OR 8.13 95%CI 1.91-34.59 p=0.05) were significant risk factors for OASIS. Conclusion: Overall incidence of OASIS in HRPB was 2.0%, which is within the normal range. Newborn’s HC was not significantly associated with the occurrence of OASIS. Birth weight and instrumental delivery were significant risk factor for OASIS. This information can be used for patient counselling and shared decision making.

Risk factors for perineal and vaginal tears in primiparous women \u2013 the prospective POPRACT-cohort study

BackgroundThe aim of this study was to estimate the incidence of second-degree perineal tears, obstetric anal sphincter injuries (OASI), and high vaginal tears in primiparous women, and to examine how sociodemographic and pregnancy characteristics, hereditary factors, obstetric management and the delivery process are associated with the incidence of these tears.MethodsAll nulliparous women registering at the maternity health care in Region Örebro County, Sweden, in early pregnancy between 1 October 2014 and 1 October 2017 were invited to participate in a prospective cohort study. Data on maternal and obstetric characteristics were extracted from questionnaires completed in early and late pregnancy, from a study-specific delivery protocol, and from the obstetric record system. These data were analyzed using unadjusted and adjusted multinomial and logistic regression models.ResultsA total of 644 women were included in the study sample. Fetal weight exceeding 4000 g and vacuum extraction were found to be independent risk factors for both second-degree perineal tears (aOR 2.22 (95% CI: 1.17, 4.22) and 2.41 (95% CI: 1.24, 4.68) respectively) and OASI (aOR 6.02 (95% CI: 2.32, 15.6) and 3.91 (95% CI: 1.32, 11.6) respectively). Post-term delivery significantly increased the risk for second-degree perineal tear (aOR 2.44 (95% CI: 1.03, 5.77), whereas, maternal birth positions with reduced sacrum flexibility significantly decreased the risk of second-degree perineal tear (aOR 0.53 (95% CI 0.32, 0.90)). Heredity of pelvic floor dysfunction and/or connective tissue deficiency, induced labor, vacuum extraction and fetal head circumference exceeding 35 cm were independent risk factors for high vaginal tears (aOR 2.32 (95% CI 1.09, 4.97), 3.16 (95% CI 1.31, 7.62), 2.53 (95% CI: 1.07, 5.98) and 3.07 (95% CI 1.5, 6.3) respectively).ConclusionThe present study corroborates previous findings of vacuum extraction and fetal weight exceeding 4000 g as risk factors of OASI. We found that vacuum extraction is a risk factor for second-degree tear, and vacuum extraction, fetal head circumference exceeding 35 cm and heredity of pelvic floor dysfunction and/or connective tissue deficiency were associated with increased risk of high vaginal tears. These findings have not been documented previously and should be confirmed by additional studies.

Risk Factors for Obstetric Anal Sphincter Injuries among Women Delivering at a Tertiary Hospital in Southwestern Uganda.

Background Obstetric anal sphincter injuries (OASIS) arise from perineal trauma during vaginal delivery and are associated with poor maternal health outcomes. Most OASIS occur in unattended deliveries in resource-limited settings. However, even in facilities where deliveries are attended by skilled personnel, a number of women still get OASIS. Objectives To determine the incidence and risk factors for obstetric anal sphincter injuries among women delivering at Mbarara Regional Referral Hospital (MRRH). Methods We conducted an unmatched hospital-based case control study, with the ratio of cases to controls of 1 : 2 (80 cases and 160 controls). We defined a case as a mother who got a third- or fourth-degree perineal tear after vaginal delivery while the controls recruited were the next two mothers who delivered vaginally without a third- or fourth-degree perineal tear. A questionnaire and participants' medical records review were used to obtain sociodemographic and clinical data. We estimated the incidence of OASIS and performed univariable and multivariable logistic regression to identify the associated risk factors. Results The cumulative incidence for OASIS during the study period was 6.6%. The risk factors for OASIS were 2nd stage of labour ≥1 hour (aOR 6.07, 95%CI 1.86–19.82, p=0.003), having episiotomy performed during labour (aOR 2.57, 95%CI 1.07–6.17, p=0.035), perineum support during delivery (aOR 0.03, 95%CI 0.01–0.12, p < 0.001), and monthly income of >50,000 shillings (aOR 0.09, 95%CI 0.03–0.28, p < 0.001). Conclusions and Recommendations. The risk factors for obstetric anal sphincter injury were prolonged second stage of labour and performing episiotomies during deliveries while higher monthly income and perineum support during delivery were protective. We recommend routine support to the perineum during delivery. Care should be taken in mothers with episiotomies, as they can extend and cause OASIS.

Changing incidence of obstetric anal sphincter injuries-A result of formal prevention programs?

Obstetric anal sphincter injuries (OASIS) are serious complications to vaginal delivery causing anal incontinence in 50% of the women in the long term. In Norway, the incidence of OASIS has been significantly reduced from 4%-5% to 1%-2% after implementation of prevention programs focusing on perineal protection. The aim of our study was to evaluate whether implementation of formal prevention programs was associated with a reduced incidence of OASIS over time. We performed a historical cohort study, evaluating incidence, change of incidence and risk factors of OASIS during the years2011-2015 at the four delivery departments in the Capital Region of Denmark. Two of the four departments implemented formal prevention programs in 2012-2013. We performed trend tests and uni- and multivariable analyses, adjusting for important risk factors and calculating interactions between risk factors. There were 75 173 vaginal deliveries during the study period; of those, 2670 (3.6%) were complicated by OASIS. The incidence of OASIS decreased during the study period from 4.3% (n=636) in 2011 to 2.6% (n=399) in 2015. There was a significant decrease in the incidence of OASIS at both the departments with formal prevention programs and those without. After adjustment for other important risk factors of OASIS, we found no significant difference in the risk reduction between departments with and without formal prevention programs. We found that the general focus on prevention of OASIS in Denmark was associated with a significant decrease in the incidence of OASIS, but implementation of formal prevention programs did not lead to a further reduction. It is possible that more rigorous interventions at the hospitals with formal prevention programs could have resulted in a significant difference in incidence of OASIS.

Factors associated with obstetric anal sphincter injuries during vacuum delivery among Chinese women.

To investigate factors associated with obstetric anal sphincter injuries (OASIS) during vacuum delivery among Chinese women. A retrospective cohort study of Chinese women who underwent vacuum-assisted vaginal delivery at a tertiary referral hospital in Taiwan between January 2010 and December 2016. Logistic regression analysis was used to compare various factors (maternal, delivery, and neonatal factors) between women with and those without OASIS. Among 18744 Chinese women with singleton vaginal delivery, 3141 (16.76%) had vacuum assistance and 2634 (83.86%) were primiparous. Of the women who had a vacuum delivery, 1073 (34.16%) sustained OASIS, of whom 967 (90.12%) were primiparous. The major independent risk factors for OASIS were primiparity (adjusted odds ratio [aOR], 2.93; 95% confidence interval [CI], 2.29-3.76) and use of midline episiotomy (aOR, 3.01; 95% CI, 1.74-5.17). However, epidural analgesia had a protective effect (aOR, 0.64; 95% CI, 0.54-0.75) against OASIS. In multivariate analysis for the primiparous subgroup, the independent significant risk factors for OASIS remained the same. A high incidence of OASIS during vacuum delivery was observed among Chinese women. Midline episiotomy was found to be a modifiable risk factor for OASIS, whereas epidural analgesia had a protective effect.

Prevention and Management of Severe Obstetric Anal Sphincter Injuries (OASIs): a National Survey of Nurse- Midwives.

There are no data on midwives' knowledge and management of obstetric anal sphincter injuries (OASIs) in the USA. We performed a cross-sectional national survey characterizing OASI practice by certified nurse midwives (CNMs), hypothesizing that few midwives personally repair OASIs and that there are gaps in CNM OASI training/education. We emailed a REDCap internet-based survey to 6909 American College of Nurse Midwives members (ACNM). We analyzed responses from active clinicians performing at least one delivery per month, asking about OASI risks, prevention, repair, and management. We summarized descriptive data then evaluated OASI knowledge by patient and provider characteristics. We received 1070 (15.5%) completed surveys, and 832 (77.8%) met the inclusion/exclusion criteria. Participants were similar to ACNM membership. Respondents most frequently identified prior OASI (87%) and nutrition (71%) as antepartum OASI risk factors and, less frequently, nulliparity (36%) and race (22%). Identified intrapartum risks included forceps delivery (94%) and midline episiotomy (88%). When obstetric laceration is suspected, 13.6% of respondents perform a rectal examination routinely. Only 15% of participants personally perform OASI repair. Overall, participants matched 64% of evidence-based answers. OASI education/training courses were attended by 30% of respondents, and 44% knew of OASI protocols within their group/institution. Of all factors evaluated, the percent of evidence-based responses was only different for respondent education/CME and protocols. Quality initiatives regarding OASI prevention and management may improve care. Our data suggest OASI training for midwives may improve delivery care in the US. Further studies of other obstetric providers are needed.

Risk Factors and Outcome of Patients with Obstetric Anal Sphincter Injuries (OASIS)

Background: Anal incontinence is an embarrassing condition that is largely underreported. Obstetric anal sphincter injuries are the most important etiological factors. Anal sphincter injury during delivery is considered to be one of the major risk factors for fecal incontinence in women. After anal sphincter injury at the time of delivery, up to 50% women have complaints of fecal incontinence, mainly because of persisting sphincter defects. &#x0D; Objectives: To evaluate the risk factors for the occurrence of obstetric anal sphincter injuries during vaginal delivery. To evaluate the outcome of patients with obstetric anal sphincter injuries. &#x0D; Methodology: A retrospective descriptive study was conducted from 2014 to 2016. Data of all patients with Obstetric Anal Sphincter Injuries (OASIS) over 3 years was collected from the medical record section after ethical clearance from Institutional Review Committee (IRC), BPKIHS. The data was entered in the excel sheet and analyzed using SPSS 17. &#x0D; Results: The Most important risk factor of OASIS was operative vaginal delivery (vacuum assisted vaginal delivery), followed by birth weight of the baby greater than 3.5 Kg and primigravida. &#x0D; Conclusion: Patients undergoing operative vaginal delivery, primigravida and birth weight greater than 3 kg are the important risk factors for OASIS. So, patients with these conditions should be handled carefully during second stage of labor to prevent the occurrence of OASIS.

Risk factors for obstetric anal sphincter injuries (OASIS) during vacuum extraction delivery in a university affiliated maternity hospital

Introduction: Instrumental delivery is a well-known risk factor for obstetric anal sphincter injuries (OASIS). The specific characteristics among patient undergoing vacuum extraction delivery (VE) are less studied. Therefore, we aimed to evaluate risk factors for OASIS among parturient that underwent a VE delivery in a large university affiliated maternity hospital.Material and methods: The study population contained 9116 women who delivered by VE in tertiary medical center from 1988 to 2015. Inclusion criteria included deliveries beyond 24-week gestation. Multiple gestations and pregnancies complicated with stillbirth were excluded from the analysis. Maternal obstetric variables were compared between parturient with and without OASIS. Independent risk factors for OASIS were assessed by multivariable logistic regression modeling.Results: OASIS was diagnosed in 94 women (1.03%) following vacuum extraction. Among patients who underwent a VE delivery, gravidity and parity were found to be significantly lower in patients with OASIS. A multivariable logistic regression model with OASIS as the outcome variable revealed that among women who underwent VE, while episiotomy and delivery of a macrosomic neonate were not independently associated with OASIS, a strong association between nulliparity and OASIS was found (OR 3.34; 95% CI 1.93–5.78; p < .001).Conclusions: OASIS is uncommon in our population. Vacuum extraction in nulliparous parturient is a significant risk factor for OASIS. Our results should be taken into account when managing nulliparous deliveries.

Republication de : Incontinence anale et lésions obstétricales du sphincter anal, épidémiologie et prévention

Our main objectives were to identify risk factors, methods for early diagnosis, and prevention of obstetric anal sphincter injuries (OASIs), using a literature review. The main risk factors for OASIs are nulliparity, instrumental delivery, posterior presentation, median episiotomy, prolonged second phase of labor and fetal macrosomia. Asian origin, short ano-vulvar distance, ligamentous hyperlaxity, lack of expulsion control, non-visualization of the perineum or maneuvers for shoulder dystocia also appear to be risk factors. There is a risk of under-diagnosis of OASIs in the labor ward. Experience of the accoucheur is a protective factor. Secondary prevention is based on the training of birth professionals in recognition and repair of OASIs. Primary prevention of OASIs is based on training in the maneuvers of the second phase of labor; if possible, instrumental extractions should be avoided. Mediolateral episiotomy may have a preventive role in high-risk OASIs deliveries. A robust predictive model is still lacking to allow a selective use of episiotomy.

Nomogram Use to Predict Obstetric Anal Sphincter Injuries prior to Term Vaginal Delivery [14R

INTRODUCTION: Obstetric anal sphincter injuries (OASIs) following vaginal delivery are a significant complication. We previously identified and published significant independent risk factors for OASIs. A validated OASIs prediction model for women with known risk factors planning vaginal delivery is needed to facilitate patient counseling and shared treatment decision-making. METHODS: We performed a retrospective cohort study including women having had vaginal deliveries (2006-2015), with demographic and obstetric data abstracted through medical record review. Results were adjusted for potential confounding factors. Nomogram developed using logistic regression analyses that included risk factors taken from published OASIs literature. Dataset was divided into training and test datasets for internal validation. Prediction nomogram was constructed using regression-based coefficient scoring system with a correlated probability of OASIs. RESULTS: Among 16,024 included vaginal delivery, 1106 (6.9%) were complicated with an OASIs. Predictors identified in the train cohort were: Asian race, nulliparous status, increased age, birth-weight, birthweight-maternal body mass index ratio (BW:BMI), smoking status, gestational age, parity, episiotomy, trial of labor after cesarean, and operative vaginal deliveries. The constructed nomogram was internally validated. CONCLUSION: This study confirmed known OASIs risk factors among women having term vaginal deliveries. Furthermore, we established and validated a novel nomogram for the prediction of OASIs for the women giving vaginal deliveries with known risk factors for severe perineal laceration. If nomogram is externally validated, it would be an excellent counseling tool for women with increased probability of OASIs.

Incontinence anale et lésions obstétricales du sphincter anal, épidémiologie et prévention

Our main objectives were to identify risk factors, methods for early diagnosis, and prevention of obstetric anal sphincter injuries (OASIs), using a literature review. The main risk factors for OASIs are nulliparity, instrumental delivery, posterior presentation, median episiotomy, prolonged second phase of labor and fetal macrosomia. Asian origin, short ano-vulvar distance, ligamentous hyperlaxity, lack of expulsion control, non-visualization of the perineum or maneuvers for shoulder dystocia also appear to be risk factors. There is a risk of under-diagnosis of OASIs in the labor ward. Experience of the accoucheur is a protective factor. Secondary prevention is based on the training of birth professionals in recognition and repair of OASIs. Primary prevention of OASIs is based on training in the maneuvers of the second phase of labor; if possible, instrumental extractions should be avoided. Mediolateral episiotomy may have a preventive role in high-risk OASIs deliveries. A robust predictive model is still lacking to allow a selective use of episiotomy.

Association between severities of striae gravidarum and Obstetric Anal Sphincter Injuries (OASIS)

Objectivesto examine the association between the severities of Striae Gravidarum (SG) and Obstetric Anal Sphincter Injuries (OASIS) and to measure the symptoms regarding urinary incontinence, fecal/flatus incontinence, and dyspareunia, at 6 and 12 months postpartum. Designthis is a cohort study. Settingfour university teaching medical centers in Israel, two in the north and two in the center of the country. Participantswomen with OASIS were interviewed and assessed for SG. OASIS was divided into 4 groups: 3A, 3B, 3C and 4. Inclusion criteria were:OASIS diagnosis, non-instrumental vaginal childbirth, birth between 37 and 42 gestational weeks, singleton newborn, neonatal birth weight of Severity scoring of SG severity scoring, using Atwal’s Numerical Scoring System,observed 4 body sites; Abdomen, Breasts, Hips, and Buttocks., Total severity score (TSS) for all sites range between 0 and 24 and categorized: 0–3: no SG (NSG) and 4 and over: SG.The Pelvic Floor Symptom Bother Questionnaire (PFBQ),a validated, structured questionnaire, was used for the 6 and 12 month follow-up assessments, with nine items regarding pelvic floor dysfunction (urinary and bowel impairment uterine prolapse and sexual function). Measurements and findingseighty women who had OASIS were enlisted, interviewed and assessed for SG. The average score for women with some SG was 6.10 (SD = 4.12). There were 58 (72.5%) women with OASIS level 3A; 12 (15%) had 3B; 4 (5.0%) had 3C and 6 (7.5%) had 4th degree anal injuries, respectively. Forty two (52.5%) of the women had SG and 38 (47.5%) had no SG. There was no association between SG severity and OASIS (3A, 3B, 3C+4th) χ2 (6) = 8.4014; p = 0.2. As there were only 10 women with OASIS of 3C and 4, we re-analyzed the association between SG severity and OASIS severity of 3A and 3B. There was a significant association between SG severity and OASIS severity (3A, 3B) χ2 (3) = 9.306; p = 0.025. Additional findingswomen with SG were younger (mean = 26.74, SD = 3.57) than women without SG (mean = 29.29, SD = 4.40) (t(78) = 2.86, p = .005). Three symptoms had a significant reduction in the bother degree between 6 and 12 months: urinary incontinence (p = 0.017), flatus incontinence (p = 0.031) and sexuality (p = 0.016). Key conclusionsthe innovation of this research is the association between SG severity and OASIS severity (3A, 3B), added information regarding OASIS risk factors.

Prevention and Management of Severe Obstetric Lacerations: A National Survey of Nurse Midwives [21L

INTRODUCTION: There is no detailed information on US obstetric providers' understanding of risks and management of severe obstetric anal sphincter injuries (OASIS). We performed a cross-sectional national survey study to identify OASIS education gaps among certified nurse midwives (CNMs) that could improve obstetric quality. METHODS: We invited American College of Nurse Midwives members (ACNM; n=6909) via email, and included active ACNM members performing at least one delivery within the past year. We assessed their understanding of OASIS risks, prevention, repair, and management based on a RedCap survey instrument that was previously created and piloted within a university OB-GYN department. RESULTS: We received 1069 (15.5%) completed surveys; 889 (83.2%) met our inclusion criteria. Participant age, race, and gender were statistically representative of ACNM membership. Poor nutrition, nulliparity, forceps and vacuum use, and midline episiotomy were reported as the top OASIS risk factors. CNM prevention techniques included perineal support, guided delivery, avoiding episiotomies, and maternal positioning. 15.1% of respondents reported repairing OASIS personally, 78.8% referred out. Over 85% of respondent reported they did not routinely perform a rectal exam if lacerations were suspected. At discharge, CNMs recommend stool softeners, sitz baths, NSAIDS, lidocaine ointment or spray, and fiber supplements. 30% of respondents reported receiving formal education on OASIS, and 37.5% reported that their delivery sites have protocols or guidelines regarding OASIS management. CONCLUSION: CNMs report standard care for OASIS that is similar to the American College of Obstetricians and Gynecologists’ recent practice bulletin recommendations, though additional formal training on OASIS prevention and management appears warranted.

Risk Factors for Obstetric Anal Sphincter Injury in a Diverse Population [1C

INTRODUCTION: We evaluated risk factors for obstetric anal sphincter injuries (OASIS) and determined the effect of duration of second stage of labor (DSS) on OASIS risk. METHODS: We included term, singleton, cephalic vaginal deliveries within Kaiser Permanente Northern California over two years. Bivariate analysis identified OASIS risk factors. Multiple logistic regression helped eliminate confounding. Classification and Regression Tree (CART) recursive partitioning created decision nodes based on risk factors. DSS was grouped into 15-minute intervals to examine effect magnitude. RESULTS: Of 22,741 deliveries included, 93.8% were spontaneous and 6.2% were vacuum-assisted. The OASIS rate was 4.9%. Multiple logistic regression identified Asian race (OR 2.4, CI 2.1-2.8), vacuum delivery (OR 4.6, CI 3.9-5.4), DSS greater than 75 minutes (OR 2.4, CI 2.1-2.8), VBAC (OR 2.8, CI 2.1-3.8), and nulliparity (OR 1.7, CI 1.4-2.1) as independent risk factors for OASIS. DSS ranged from 0-680 minutes. Median length was 95 minutes for nulliparous and 27 minutes for multiparous women. The first CART decision node was DSS greater than 75 minutes. Each additional 15 minutes of pushing resulted in 1.07 (p &lt; 0.001) increase in the odds of OASIS in nulliparous women and 1.14 (p &lt; 0.001) in multiparous women. CART analysis identified Asian women delivered via vacuum after a greater than 75 minute second stage as the subpopulation with highest risk of OASIS at 43%. CONCLUSION: Risk factors for highest rates of OASIS were identified. Each incremental increase in DSS confers an increase in OASIS risk. Changing management based on our findings could improve outcomes for laboring women.

Can we predict obstetric anal sphincter injury?

ObjectiveThe aim of the study was to identify primiparous pregnant women with a higher risk for obstetric anal sphincter injuries (OASIS) based on obstetric characteristics (risk factors). Study designIn the retrospective case control study primiparous women were examined using endoanal ultrasonography (EUS) for OASIS identification 6–12 weeks after delivery. Obstetric characteristics for OASIS were collected from the mothers’ medical records. The univariate analysis of maternal (age at delivery, maternal height, weight, BMI), infant (length, weight and head circumference) and birth (pregnancy duration, labour and delivery duration, episiotomy, vacuum extraction and oxytocin augmentation) risk factors, Pearson correlations and information gain were carried out. The cut-off values for the aforementioned risk factors divided the patients into groups with higher and lower risk of OASIS. ResultsThe data of 84 primiparous women with OASIS, and 58 without, were analysed. Those newborns born to women in the OASIS group were heavier (P<0.05), with the cut-off at 3420g (72% probability of OASIS), had a larger head circumference (P<0.001), cut-off at 36cm (84% probability of OASIS), and were longer (P<0.05), cut-off at 50.5cm (74% probability of OASIS). The maternal age and body mass index (BMI) were risk factors for OASIS (P<0.05 and P<0.05, respectively) with a probability of 83% in women younger than 27.5 years and a 78% probability if BMI was higher than 28kg/m2. The incidence of OASIS was not higher in women with episiotomy or vacuum extraction, but it was higher in oxytocin augmentation (P<0.031). ConclusionThe findings can assist in identification of pregnant women with a higher risk of OASIS who require special attention at delivery to prevent it. In high risk women EUS is indicated to identify and treat possible OASIS as early as possible in order to prevent anal incontinence.

Evaluation of training programme uptake in an attempt to reduce obstetric anal sphincter injuries: the SUPPORT programme

The objective was to assess the feedback from a quality improvement training programme to reduce obstetric anal sphincter injuries (OASIS). Training sessions were organised that included evidence-based information on OASIS risk factors and training on models to measure perineal body length (PBL), perform episiotomies with standard and 60° fixed angle scissors (EPISCISSORS-60®), and measure post-delivery episiotomy suture angles with protractor transparencies. Feedback forms using a Likert scale (1-4) were completed and analysed. The setting was an evidence-based quality improvement programme (Strategy for Using Practical aids for Prevention of OASIS, Recording episiotomies and clinician Training [SUPPORT]) at two National Health Service (NHS) Hospitals in the UK. The participants were midwives and doctors attending the SUPPORT training programme RESULTS: All of the participants (100%) would recommend the training programme to a friend or colleague. 92% felt that the training session improved their knowledge of the impact of PBL and perineal distension and their knowledge of the relationship between episiotomy angle and OASIS "a lot" or "somewhat". Based on this feedback, we recommend the addition of the knowledge content of the SUPPORT programme to other centres providing perineal assessment and repair courses.

An obstetric sphincter injury risk identification system (OSIRIS): is this a clinically useful tool?

Introduction and hypothesisTo establish the contribution of maternal, fetal and intrapartum factors to the risk of incidence of obstetric anal sphincter injuries (OASIS) and assess the feasibility of an OASIS risk prediction model based on variables available to clinicians prior to birth.MethodsThis was a population-based, retrospective cohort study using single-site data from the birth database of Aarhus University Hospital, Denmark. The participants were all women who had a singleton vaginal birth during the period 1989 to 2006. Univariate and multivariate logistic regression analyses were performed using multiple imputations for missing data and internally validated using bootstrap methods. The main outcome measures were the contributions of maternal, fetal and intrapartum events to the incidence of OASIS.ResultsA total of 71,469 women met the inclusion criteria, of whom 1,754 (2.45 %) sustained OASIS. In the multivariate analysis of variables known prior to birth, maternal age 20 – 30 years (OR 1.65, 95 % CI 1.44 – 1.89) and ≥30 years (OR 1.60, 95 % CI 1.39 – 1.85), occipitoposterior fetal position (OR 1.34, 95 % CI 1.06 – 1.70), induction/augmentation of labour (OR 1.46, 95 % CI 1.32 – 1.62), and suspected macrosomia (OR 2.20, 95 % CI 1.97 – 2.45) were independent significant predictors of OASIS, with increasing parity conferring a significant protective effect. The ‘prebirth variable’ model showed a 95 % sensitivity and a 24 % specificity in predicting OASIS with 1 % probability, and a 3 % sensitivity and a 99 % specificity in predicting OASIS with a 10 % probability.ConclusionsOur model identified several significant OASIS risk factors that are known prior to actual birth. The prognostic model shows potential for ruling out OASIS (high sensitivity with a low risk cut-off value), but is not useful for ruling in the event.

Obstetric anal sphincter injuries: review of anatomical factors and modifiable second stage interventions

Obstetric anal sphincter injuries (OASIs) are the leading cause of anal incontinence in women. Modification of various risk factors and anatomical considerations have been reported to reduce the rate of OASI. A PubMed search (1989–2014) of studies and systematic reviews on risk factors for OASI. Perineal distension (stretching) of 170 % in the transverse direction and 40 % in the vertical direction occurs at crowning, leading to significant differences (15–30°) between episiotomy incision angles and suture angles. Episiotomies incised at 60° achieve suture angles of 43–50°; those incised at 40° result in a suture angle of 22°. Episiotomies with suture angles too acute ( 60°) are associated with an increased risk of OASI. Suture angles of 40–60° are in the safe zone. Clinicians are poor at correctly estimating episiotomy angles on paper and in patients. Sutured episiotomies originating 10 mm away from the midline are associated with a lower rate of OASIs. Compared to spontaneous tears, episiotomies appear to be associated with a reduction in OASI risk by 40–50 %, whereas shorter perineal lengths, perineal oedema and instrumental deliveries are associated with a higher risk. Instrumental deliveries with mediolateral episiotomies are associated with a significantly lower OASI risk. Other preventative measures include warm perineal compresses and controlled delivery of the head. Relieving pressure on the central posterior perineum by an episiotomy and/or controlled delivery of the head should be important considerations in reducing the risk of OASI. Episiotomies should be performed 60° from the midline. Prospective studies should evaluate elective episiotomies in women with a short perineal length and application of standardised digital perineal support.

Risk factors for obstetric anal sphincter injury: To prolong or to vacuum?

IntroductionAn awareness of risk factors for obstetric anal sphincter injuries (OASIS) is essential in order to reduce the occurrence of the primary event. These risk factors are demographic, obstetric and intrapartum related. We aimed to identify the risk factors for OASIS and to examine how modifiable risk factors may be used in order to reduce the incidence of OASIS. MethodsA retrospective, matched case–control study was conducted in the delivery ward of a single university teaching hospital in Israel, using data from January 2004 to July 2012. All singleton vaginal deliveries at term with OASIS were included. The controls included women matched at a ratio of 1:2 based on gestational age and deliveries that occurred immediately before and after the delivery of the women in the study group. ResultsOverall, 113 OASIS were identified. Stepwise conditional logistic regression revealed that the first vaginal birth (OR = 7.6; 95% confidence interval (CI), 3.5–16.3; p < 0.001) particularly after a previous caesarean section (OR = 13.6; 95% CI, 4.7–39.3; p < 0.001) and the length of the second stage (OR 1.5; 95% CI, 1.1–2.1, p = 0.045) were the only risk factors for OASIS. Among 24 primiparous women who already had a prolonged second stage, 15 delivered by vacuum extraction and nine spontaneously; OASIS occurred in eight (53%) and three (33%) women, respectively. Multivariate analysis showed that this difference was not significant (OR = 2.3; 95% CI, 0.4–12.7; p = 0.35). ConclusionsThe first vaginal birth particularly after a caesarean delivery and the length of the second stage increased the risk of OASIS. Vacuum extraction performed to shorten a prolonged second stage is not necessarily protective.