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Obstetric Anal Sphincter Injury as a Quality Metric

16-Year Experience at a Single Institution

Pennycuff, Jon F. MD; Northington, Gina M. MD, PhD; Loucks, Tammy MPH, DrPH; Suciu, Gabriel PhD, MSPH; Karp, Deborah R. MD

doi: 10.1097/AOG.0000000000001199
Contents: Original Research

OBJECTIVE: To evaluate trends in annual rates of vaginal birth, cesarean delivery, and obstetric anal sphincter injury at a single institution before and after the designation of obstetric anal sphincter injury as a measure of obstetric quality and safety.

METHODS: This was a retrospective cohort study of women undergoing a singleton vaginal delivery and diagnosed with obstetric anal sphincter injury over a 16-year period. International Classification of Diseases, 9th Revision codes for perineal lacerations were used as identifiers. Trends in annual cesarean delivery, perineal laceration, and obstetric anal sphincter injury rates were assessed in a linear regression model. The data were divided into two time periods (1998–2005 and 2006–2013) based on the year (2006) in which obstetric anal sphincter injury was designated as a quality marker and compared.

RESULTS: A total of 1,366 women had obstetric anal sphincter injury, and 1,360 were included for analysis. There was a 12.1% decline in annual vaginal delivery rates (from 77.1% to 67.8%) and a 40.6% increase in annual cesarean delivery rate (from 22.9% to 32.2%; P<.001). The rate of first-degree and second-degree laceration increased significantly (P=.009), and obstetric anal sphincter injury decreased significantly (P<.001). Operative vaginal birth and episiotomy were associated with obstetric anal sphincter injury in 2006–2013 compared with 1998–2005 (P<.001 and P=.018, respectively).

CONCLUSION: After the designation of obstetric anal sphincter injury as an institutional quality measure, rates of obstetric anal sphincter injury decreased.

After its designation as a quality metric, the rate of third-degree and fourth-degree lacerations significantly decreased, despite an increase in operative vaginal delivery and episiotomy.

Division of Female Pelvic Medicine & Reconstructive Surgery and the Division of Research, Department of Gynecology and Obstetrics, Emory University School of Medicine Atlanta, Georgia; and the School of Public Health, Nova Southeastern University, Fort Lauderdale, Florida.

Corresponding author: Deborah R. Karp, MD, Woodruff Memorial Research Building, 1639 Pierce Drive, Room 4305, Atlanta, GA 30322; e-mail:

Financial Disclosure The authors did not report any potential conflicts of interest.

Presented at the American Association of Gynecologic Laparoscopists Annual Scientific Meeting, November 17–21, 2014, Vancouver, British Columbia, Canada.

Perineal trauma is a common outcome of vaginal delivery with third- and fourth-degree lacerations—termed obstetric anal sphincter injury—being the most serious. The incidence varies widely (0.25–24.5%) and is increasing.1–10 Obstetric anal sphincter injury can lead to perineal wound breakdown, fistula, chronic pain, anal incontinence, sexual dysfunction, and decreased quality of life.11–20 Forceps delivery, nulliparity, fetal macrosomia, and persistent occiput-posterior position are risk factors for obstetric anal sphincter injury, and obstetric techniques that may reduce its risk include mediolateral episiotomy and manual assistance during delivery.7,11 The prevention of obstetric anal sphincter injury or, at the very least, correct diagnosis and treatment could mitigate these outcomes.

The Agency for Healthcare Research and Quality, a governmental health care organization whose mission is to perpetuate safety, equality, and accessibility in health care, has designated obstetric anal sphincter injury as a measure of obstetric quality and maternal safety.21–24 Our institution designated obstetric anal sphincter injury to be a quality and safety metric in 2006 as part of an overarching perinatal quality improvement initiative.

We sought to examine annual delivery rates and trends with obstetric anal sphincter injury in the 8 years before and after this designation at a mixed community and academic training hospital. We secondarily assessed factors associated with it during these time periods. We hypothesized that the rate of obstetric anal sphincter injury would increase as a result of heightened awareness and focus on patient safety and quality after implementation of this quality metric.25

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This study is a retrospective cohort study performed over a 16-year time period at a teaching hospital. After Emory University institutional review board approval, deliveries occurring between January 1998 and December 2013 were evaluated electronically from our administrative data warehouse. All deliveries associated with International Classification of Diseases, 9th Revision codes consistent with first-, second-, third-, and fourth-degree and not otherwise specified perineal laceration (664.00, 664.10, 664.20, 664.30, 664.40, respectively) were abstracted. At our institution, a third-degree perineal laceration is defined as any obstetric laceration involving the anal sphincter complex; a fourth-degree tear is any laceration involving the anal sphincter complex and the rectal mucosa. Diagnosis was made at the discretion of the health care provider attending the birth and recorded within the medical record. Episiotomy was documented independent of perineal laceration. Annual perineal lacerations were calculated and presented as a percentage of vaginal births. Data were also used to calculate annual rates of vaginal and cesarean deliveries.

All women who underwent a singleton, vaginal birth complicated by a third- or fourth-degree perineal laceration between 1998 and 2013 were identified. Patient data including demographic and clinical data such as maternal age and race, year of delivery, length of hospital stay, use of episiotomy, and operative vaginal delivery, were collected through query of our institution's integrated clinical data warehouse. The clinical data warehouse is a centralized, standardized, and integrated repository for data and is extracted from various clinical and administrative source systems within our health care system. The data are entered by licensed medical coders who manually input the data based on physician clinical documentation. The security and integrity of this database are maintained by automated daily electronic feeds ensuring data loading accuracy. Study data were abstracted from this clinical data warehouse and then, in order to validate the accuracy of these data, review of electronic medical records (when available) was performed by the first author. Because our institution did not begin electronic medical recording until after 2008, only data from 2008 to 2013 could be verified. During this validation process, no discrepancies in clinical data were noted.

Trends in annual cesarean delivery, perineal laceration, and obstetric anal sphincter injury rates over the 16-year study period were assessed with the F test in a linear regression model. For diagnosis of the model, we used Student residuals. The data were then divided into two time periods (predesignation 1998–2005 and postdesignation 2006–2013) based on the year (2006) in which obstetric anal sphincter injury was designated as an obstetric quality marker. Data were analyzed within each period and then compared using bivariate analysis. Continuous variables were compared using a two-sample t test or a nonparametric test if the normality was violated. The categorical variables were analyzed with the χ2 test of independence. All hypotheses tests were two-sided, and type I error was considered 0.05. SAS 9.4 was used for this analysis.

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Between 1998 and 2013, a total of 50,216 deliveries occurred at our institution. Over this 16-year time period, 16,264 women sustained obstetric perineal lacerations of any type. A total of 1,366 women sustained obstetric anal sphincter injury. Of these, 1,360 women are included in this analysis. Four were excluded as a result of multiple gestations, one as a result of a misclassified diagnosis (cesarean delivery), and one for incomplete or inconsistent data. During the 16-year study period there was a decline in annual vaginal delivery rates and an increase in the annual cesarean delivery rate, which was statistically significant (P<.001) (Fig. 1). Between 1998 and 2013, the vaginal delivery rate decreased by 12.1% (from 77.1% to 67.8%) and the cesarean delivery rate increased by 40.6% (from 22.9% to 32.2%).

Fig. 1

Fig. 1

Annual rates of perineal lacerations by type (first- and second-degree compared with third- and fourth-degree) and trends over time are displayed in Figure 2. Over the 16-year study period, first- and second-degree perineal laceration rates increased significantly (P=.009) whereas third- and fourth-degree perineal laceration (obstetric anal sphincter injury) rates showed a steady decrease (P<.001). Cesarean delivery rates increased significantly (P<.001). The data fit very well in the linear trend model for rates. Table 1 shows the mean annual rate and trend analysis for cesarean delivery, perineal, and obstetric anal sphincter injury rates over the 16-year study period. The average annual obstetric anal sphincter injury rate was 4.0 per 100 vaginal births (standard deviation±0.89). When stratified by type of laceration, the majority of obstetric anal sphincter injuries were third-degree lacerations (79.5%) compared with 20.5% fourth-degree lacerations. The proportion of third- to fourth-degree lacerations did not change significantly over the study time period (P=.15).

Fig. 2

Fig. 2

Table 1

Table 1

Women diagnosed with obstetric anal sphincter injury between 1998 and 2005 were clinically similar in terms of age and hospital length of stay compared with those diagnosed with obstetric anal sphincter injury between 2006 and 2013. There was, however, a significant difference in racial composition noted between the two time cohorts, with Caucasians significantly more affected by obstetric anal sphincter injuries in the later time cohort compared with African American and other races (Table 2) The majority of obstetric anal sphincter injuries occurred with community obstetricians in both time periods; however, there was a significant increase in obstetric anal sphincter injuries noted with academic faculty obstetricians in the later time period. Deliveries complicated by obstetric anal sphincter injury in 2006–2013 were more likely to be operative vaginal delivery (specifically forceps) and with concomitant episiotomy when compared with the earlier cohort (P<.001 and P=.018, respectively) (Table 2).

Table 2

Table 2

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Our single-institution study revealed a steady decline in rates of coded obstetric anal sphincter injury over a 16-year time period. We did not observe an increase in the rates of obstetric anal sphincter injury after its designation of a marker of quality and safety at our institution. Interestingly, the annual rates of first- and second-degree perineal lacerations began to increase in 2002 but showed an even greater rise in 2007—just 1 year after obstetric anal sphincter injury was designated as a quality metric at our institution.

Our study findings bring into question the true utility of obstetric anal sphincter injury as a quality metric. Our results may indicate a limitation of our study question or they may be reflective of a concerning byproduct of designating obstetric anal sphincter injury as a quality metric, which may ultimately discourage health care providers from accurate diagnosis as a result of concern for professional recriminations. In addition to raising concern for down-classification of lacerations, our results may also be the result of misdiagnosis from inadequate training on sphincter injury and repair.26 Given the lag time in the development of clinical sequelae of improperly treated obstetric anal sphincter injury, this is concerning for quality of care.

The strengths of this study are the large sample size and extended time period. As a result, we were able to determine small but significant changes in rare events that would be difficult to study prospectively. Because our data were generated from an electronic database and are based on diagnosis and procedure codes, our study is limited by potential data entry and coding errors. In addition, we were not able to include important clinical data such as gravidity–parity and birth weight in our analysis, because it was not universally available for all patients. Although we were able to determine the association of episiotomy with obstetric anal sphincter injury, we do not know what type of episiotomy was performed. An additional limitation of our study is that it is a single-center study, which may limit the generalizability of our findings.

We believe that the greatest utility of obstetric anal sphincter injury as an indicator of maternal quality may be in its secondary effects to raise awareness and education and not in its use as a metric of an individual health care provider or institution. A major concern of the use of obstetric anal sphincter injury as a quality and safety metric is that there are relatively few modifiable risk factors and the metric itself is not actionable.27 Although initially endorsed by the Joint Commission, the National Quality Forum, and the Agency for Healthcare Research and Quality, it has been abandoned by all but one such agency.

As the role of quality, safety, and value in medicine continues to evolve, the discussion of quality and safety metrics—such as obstetric anal sphincter injury—will become more prominent. If the purpose of quality measures is to standardize and improve patient care, we believe that assessing obstetric anal sphincter injury rates alone is insufficient. A recent study by Friedman et al28 concluded that using obstetric anal sphincter injury as a quality indicator was of limited use as a result of not only the nationwide low variability in obstetric anal sphincter injury rates, but also by the fact that reducing the major modifiable factor (ie, operative vaginal delivery) would likely lead to a consequent rise in cesarean delivery. Their study further suggests that obstetric anal sphincter injury is not an actionable quality marker.

As has been previously suggested, monitoring obstetric anal sphincter injury rates may help signal where educational programs are needed. However, appropriate attention and close follow-up in the postpartum period is an additional important component to ensure proper healing and normal function of the pelvic organs.29 Using obstetric anal sphincter injury as a health care quality indicator may help assure patients who have sustained a high-grade perineal laceration receive appropriate analgesia, undergo correct primary repair, and receive referral for specialized care such as in a perineal laceration clinic or with a female pelvic medicine subspecialist. More universal designation of obstetric anal sphincter injury as a metric of obstetric quality and safety with an emphasis on increasing its detection through heightened education and training and routing patients to appropriate follow-up may be one way to achieve this.

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