A summary of subsequent deliveries, grouped by the number of deliveries per subject, is provided in Table 3. A total of 7,193 women had 1 subsequent delivery, and 2,837 women had 2 or more deliveries. Interestingly, among the 13 women with 7–9 deliveries during the study period 1990-2002, only 2 patients had recurrence of severe perineal laceration (Table 3). One of them experienced 2 third-degree lacerations in 7 vaginal deliveries, and another subject experienced 2 fourth-degree lacerations in 9 vaginal deliveries.
Among the 14,990 subsequent vaginal deliveries, there were 6.65% (n = 997) vacuum-assisted deliveries, 2.37% (n = 356) forceps deliveries, and the rate of episiotomy was 50% (n = 7,496) (Table 4). Of 356 forceps deliveries, 313 were low forceps, 27 mid forceps, and 94 were forceps rotations or forceps application for the after-coming head.
Eight hundred sixty-four subjects had a third- or fourth-degree perineal laceration, a rate of 5.76%. This was a 21% drop in rate of severe perineal lacerations (OR 0.78, 95% CI 0.72–0.83). During the same time period, there was a 69% drop in the rate of forceps deliveries and 28% drop in the rate of vacuum deliveries (Table 5).
Table 6 describes the relation of various risk factors to the occurrence of initial lacerations and recurrent lacerations. Forceps had a higher risk of laceration than vacuum in both the groups, and the use of episiotomy with instrumentation further increased the risk. Interestingly, for subjects with primary anal sphincter laceration, episiotomy in the absence of instrumentation was protective (OR 0.9, 95% CI 0.88–0.93), whereas, for recurrent lacerations, the risk is increased 1.7 times with the use of episiotomy.
Multivariate logistic regression was used to estimate the relation of age, forceps, episiotomy, vacuum, and year of delivery to the occurrence of laceration (Table 7). All of the predictors were significant predictors of the occurrence of a laceration. These estimates are independent predictors (adjusted for the other factors). As shown, a patient has 2.5 times the chance of the occurrence of a laceration if forceps was used in a subsequent delivery, 2.1-fold increase with episiotomy, and 1.9 times with use of vacuum.
This is one of the largest studies examining the risk of recurrence of anal sphincter lacerations. This study was feasible because, in the state of Pennsylvania, each subject who is entered into the Pennsylvania Health Care Cost Containment Council database has a unique identifier, and this allows for tracking data on subsequent pregnancies. Therefore, patients delivered subsequently at any of the hospitals in the state are included. Obviously, patients who have moved and delivered out of state are missed.
It appears that the rate of sphincter lacerations in women with prior anal sphincter injury is not higher than that seen in the general obstetrical population in Pennsylvania. Actually the rate of recurrent lacerations was lower than the rate of initial laceration (5.76% versus 7.31%, OR 0.78, 95% CI 0.72–0.83, P = .001). The decrease is probably due to the difference in the time period between initial (1991–1992) and recurrent lacerations (1992–2002) and change in the rate of major risk factors during this time. As shown in Table 5, the rate of forceps delivery dropped from 7.75% to 2.4% (69% decrease), vacuum delivery decreased by 28%, and rate of episiotomy decreased by 24% during the study period. This corresponds to a national trend in the occurrence of sphincter tears and instrumental vaginal deliveries.8
In contrast to our study, earlier studies have reported an increase in the rate of severe perineal laceration in subsequent deliveries after an initial laceration, but the number of cases reported was small. Peleg et al9 performed a retrospective study on 4,015 nulliparous women who had 2 consecutive vaginal deliveries at their institution during the study period. The patients were divided into a study group of 774 who had severe anal sphincter laceration during their first delivery and a control group of approximately 3,300 who did not. The authors reported that women with severe perineal laceration in their first delivery were at greater than twice the risk for sustaining laceration during subsequent delivery (7.5% versus 3.2%).
We searched Ovid MEDLINE for articles in English from 1966 to August 2004, using the terms “anal sphincter tears,” “perineal tears,” “perineal lacerations,” and “anal sphincter lacerations,” and the retrieved articles were hand-searched for data regarding recurrence of lacerations. We found only 3 articles reporting on the actual rate of recurrent lacerations. Payne et al10 from Oklahoma, reported a 10.7% rate of recurrent lacerations (n = 19) among 178 women with prior sphincter tears, while Harkin et al11 reported recurrent lacerations in 2 of 45 women (4.4%). As noted above, Peleg et al9 reported recurrent lacerations in 58 of 774 women (rate = 7.5%). Therefore, there was an aggregate of 79 lacerations among 997 women with prior sphincter tears, a rate of 7.9%. In our study, there were 864 lacerations among 14,990 deliveries, a rate of 5.76%.
Use of episiotomy without instrumentation is the only factor that had a significantly higher risk for laceration in subsequent delivery than the risk in initial delivery (OR 0.9 for initial laceration and OR 1.7 for recurrence, Table 6). This is possibly due to the extension of episiotomy into the anal sphincter in patients with scarred perineum. Instrumental delivery had approximately similar risk for recurrent laceration as for initial laceration, risk with forceps being higher than with vacuum (Table 6). Highest risk of laceration was noted in women where episiotomy was used, along with forceps (17.7%) or vacuum (13.3%) at the time of delivery.
One of the limitations of our study is lack of information regarding important confounders such as parity, birth weight, or indication for operative vaginal delivery in the database. The database is a composite of all the information submitted by individual hospitals in the state. Naturally, quality of data is dependent on the diligence with which data are collected at each hospital and how carefully it is entered at each hospital. We acknowledge these limitations.
Despite these limitations, it appears that use of instrumentation with episiotomy is destructive to the perineum, irrespective of whether there was prior severe perineal laceration or not. To protect the perineum and anal sphincter, it may be wise to substitute vacuum for forceps whenever possible and avoid episiotomy in women with prior anal sphincter laceration.
Our study provides reassurance that the risk of damage to the perineum and anal sphincter during subsequent vaginal delivery in women who had prior third- or fourth-degree laceration is not substantially different. Therefore, cesarean delivery should be reserved for other obstetrical indications. It is highly desirable to conduct a prospective trial in women with anal sphincter injury to determine the rate of recurrent lacerations, various risk factors associated with recurrence, and presence or absence of or deterioration of symptoms with subsequent vaginal delivery. Because of the rarity of the condition and the time involved, this is only feasible with a multicenter trial design.
Prior anal sphincter laceration does not result in an increased rate of recurrent laceration. Use of forceps, vacuum, or episiotomy increased the rate of recurrent lacerations. Prevention strategies should include avoiding instrumental vaginal delivery, substituting vacuum for forceps delivery, and restrictive use of episiotomy in women with prior anal sphincter lacerations.
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© 2005 The American College of Obstetricians and Gynecologists
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