Despite a recent decrease in episiotomy rates in the United States, it remains one of the most likely surgical procedures a woman will undergo during her lifetime.1 The episiotomy, a surgical incision in the perineum made to enlarge the vaginal opening and facilitate delivery, was originally introduced as a method assumed to improve maternal and neonatal outcomes and rapidly became a part of standard obstetric care. However, since the 1980s, routine use of episiotomy has been challenged, based on the lack of evidence of benefits of the procedure2 and the publication of multiple studies reporting increased blood loss at delivery, perineal scar breakdown and infection, postpartum pelvic pain, and dyspareunia.3–6 Recent studies have also demonstrated increased incidence of third- and fourth-degree lacerations associated with the use of midline episiotomy.7,8 The resulting damage to the internal and external anal sphincters can lead to devastating long-term sequelae, including fecal incontinence and rectovaginal fistulae.9 Among purported benefits of episiotomy, some clinicians have claimed that meticulous repair of a surgical episiotomy yields improved wound healing when compared with an unpredictable spontaneous laceration.10 This assertion, however, has not been substantiated by empiric evidence.11 Inferior biomechanical properties of healed tissue after trauma, as compared with uninjured tissue, have been well established in the field of orthopedics.12,13 This raises the following concern: not only is there no proven benefit to episiotomy, but the suggestion is that this procedure may result in weakened tissue, more susceptible to injury in a subsequent delivery.
Although episiotomy is a well-established risk factor for third- and fourth-degree perineal laceration through extension of the surgical incision at the time of delivery,14 there are very limited data on the effect of episiotomy on the risk of obstetric laceration in subsequent deliveries.15
The primary goal of our study was to examine the relationship between episiotomy without extension in the first vaginal delivery and risk of spontaneous obstetric laceration in a subsequent delivery. Our hypothesis was that prior episiotomy would increase the risk of subsequent spontaneous laceration, independent of other confounding risk factors.
MATERIALS AND METHODS
The Magee Obstetrical Maternal and Infant database contains extensive information on each woman delivering at Magee-Womens Hospital, and allows for linking of data from multiple pregnancies. We obtained approval for this historical cohort study from the University of Pittsburgh Institutional Review Board. Data from consecutive first and second deliveries occurring at Magee-Womens Hospital from 1995 to 2005 were deidentified and included in our data set. We limited our analysis to pregnancies that resulted in vaginal deliveries of liveborn term singleton fetuses from vertex presentation.
Spontaneous perineal laceration in the second vaginal delivery was designated the primary outcome of interest. The primary exposure of interest was episiotomy at first vaginal delivery. In addition, potential confounding variables, consisting of known risk factors for obstetric laceration from both deliveries, were included in the data set: maternal age, race, marital status, socioeconomic status, education level, insurance status, smoking history, type of obstetric care provider (resident service or private practitioner), type of delivery (spontaneous or operative), history of obstetric lacerations, analgesia, induction of labor, infant’s birth weight, and interpregnancy interval. Women who had episiotomy at second delivery were excluded from the final analysis.
Statistical analyses were performed using Stata 9.0 statistical software (StataCorp LP, College Station, TX). Univariable analysis of all potential risk factors for the development of perineal laceration was conducted using χ2 tests for categorical variables, and two-sample t tests for continuous variables. Some continuous variables were converted to categorical variables using clinically relevant cutoffs. Stepwise backward elimination, categorized dependent, multinomial logistic regression modeling was then used to estimate the independent contribution of each risk factor, including all variables that differed between patients who did and did not have an episiotomy at the first delivery at significance level of 0.05, to the outcome of interest.16 Multinomial categorized dependent logistic regression was selected for the analyses because our dependent variable had three categories. Results are presented as mean±standard deviation (SD) for continuous variables or as percentages for categorical variables. Statistical analyses of regression models were considered significant at the level of 0.01 secondary to the large sample size.
The data set for this analysis was abstracted from all deliveries at Magee-Womens Hospital from 1995 to 2005 (N=88,618). Among these, 19,438 women had consecutive deliveries at Magee-Womens Hospital, and a subset of 8,718 women had their first and second singleton, term vaginal deliveries during this time period. Table 1 depicts demographic characteristics of all patients in the cohort that met inclusion criteria, by episiotomy status at first delivery. Women who had episiotomy at first delivery were older, more likely to be white, married, and have higher education and commercial insurance. These demographic characteristics were also all associated with having a private practice provider, and notably, 94.6% (n=4,929) of women who had an episiotomy at first delivery were patients of private practitioners. After excluding all women with episiotomy in the second delivery, 6,052 patients remained and were included in the final analysis. The rate of episiotomy at first delivery in this final population was 47.8% (n=2,893).
Among women with prior episiotomy, 44.2% (n=1,279) had intact perineum or first-degree laceration (laceration limited to vaginal epithelium) in the second delivery, compared with 71.4% (n=2,248) of women without prior episiotomy (P<.001). Second-degree spontaneous laceration occurred in 51.3% (n=1,484) of women with prior episiotomy, compared with 26.7% (n=846) of women without prior episiotomy (P<.001). Severe perineal laceration (third or fourth degree) occurred in 4.8% (n=140) of women with prior episiotomy compared with 1.7% (n=55) of women without prior episiotomy (P<.001).
The following variables were found to be statistically significant in univariable analyses: maternal age, race, marital status, level of education, insurance, smoking status, provider type, interpregnancy interval, induction of labor, regional anesthesia, operative vaginal delivery, episiotomy in the first delivery, birth weight, and sex of infant. The result of the final multivariable logistic regression model for prediction of perineal laceration is presented in Table 2 with the associated odds ratios (ORs).
In the multivariable analysis, episiotomy without extension in the first delivery remained a significant independent risk factor for the development of spontaneous greater than first-degree laceration in the subsequent delivery. Prior episiotomy was associated with subsequent second-degree laceration with an adjusted OR of 4.47 (95% CI 3.78–5.30). For the outcome of third- and fourth-degree perineal laceration, the adjusted OR was 5.25 (95% CI 2.96–9.32). Because obstetric care provider status (private practitioner compared with resident service) seemed to affect the rate of episiotomy in the first delivery, we performed sensitivity analysis restricting our sample to the private practice subgroup only. In this more homogeneous cohort, episiotomy in the first delivery remained a significant independent risk factor for spontaneous laceration in the second delivery, with an OR of 4.67 (95% CI 3.85–5.66) for second-degree laceration and 4.76 (95% CI 1.62–14.0) for third- and fourth-degree laceration.
The risks of episiotomy in an index pregnancy are well established.3–6 However, few studies have examined the effect of episiotomy on the risk of perineal laceration in a subsequent vaginal delivery. Our results indicate a greater than fourfold risk of perineal laceration attributable to episiotomy at first delivery. The findings of our analysis demonstrate yet another detrimental aspect to episiotomy, in that the consequences of this procedure are not limited to the index delivery but rather perpetuated to subsequent vaginal deliveries. Based on these findings, for every four episiotomies not performed, one second-degree laceration would be prevented. To prevent one severe laceration, performing 32 fewer episiotomies is required.
Although spontaneous second-degree laceration and episiotomy would seem to confer similar relative risk for obstetric laceration in a subsequent delivery, the incidence of spontaneous second-degree laceration at first delivery was only 19% in our cohort compared with a 59.7% rate of episiotomy. Furthermore, episiotomy in the first delivery was not protective against third- or fourth-degree laceration in the index delivery (data not shown). Thus, this high rate of episiotomy at first delivery is the single factor responsible for increased risk of significant laceration in the second delivery for up to 40% of women in our study. Despite the decrease in the episiotomy rate from 74.7% in 1995 to 37.6% in 2005 in our cohort, the continued use of episiotomy highlights the relevance of our results to contemporary obstetric practice.
Our findings concur with data from previous publications, implicating white race, history of perineal lacerations, operative vaginal delivery, and infant birth weight as significant risk factors for spontaneous perineal lacerations.1,8,17 We did not find a contribution of Asian race to perineal laceration risk, as has been previously reported, but the limited number of Asian women in our population likely limited our power to detect a difference.17 Other studies have also established that the primary determinant for the use of episiotomy in obstetric practice is the obstetric care provider and not patient characteristics.18,19 In our cohort, the rate of episiotomy in the first delivery was significantly higher among private practitioner patients than those cared for by the resident service (67.6% compared with 19.7%).
Strengths of our study include a large sample size and representation of both academic and private practices. African-American women were also adequately represented in our study (12.7%); however, Asians and women of Hispanic ethnicity were underrepresented. Our study was limited to the first and second consecutive deliveries at Magee-Womens Hospital, and there were no patients with missing data on obstetric lacerations. The main advantage of the Magee Obstetrical Maternal and Infant database is that it includes data from all deliveries occurring at Magee-Womens Hospital, and contains variables including demographic, clinical, obstetric, and neonatal characteristics.
The limitations of our study are those inherent in the use of retrospective databases. The quality of a database depends on the accuracy of data collection, entry, and coding, and therefore misclassification may occur. The Magee Obstetrical Maternal and Infant database does not track postpartum or long-term complications.
Our results provide compelling evidence that episiotomy in a first vaginal delivery significantly and independently increases the risk of spontaneous greater than first-degree perineal laceration in a subsequent delivery. This finding adds to the evidence that episiotomy is associated with maternal morbidity and recognition that the risk of this procedure is not limited to the index delivery, but is perpetuated to future deliveries. We encourage obstetric care providers to further restrict the use of episiotomy.
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