Sylvie Martin, MSc

Women frequently incur perineal trauma at delivery. Such trauma is associated with perineal pain that may still be present 3 months postpartum,^1-4 dyspareunia,^1,2 perineal infection,^4,5 and following severe lacerations, fistula and incontinence of flatus and feces.^6,7 Episiotomy accounts for a large proportion of perineal trauma. Wide variations exist in the use of episiotomy according to country,⁵ hospital,⁸ or birth attendant.^1,9-12 There is no evidence that it is effective in preventing severe lacerations^13,14 and pelvic floor relaxation^1,7,13 or that recovery is more rapid and morbidity less than that following spontaneous tears.^5,7 Also, median episiotomy increases the risk of severe perineal lacerations,¹⁴ particularly in primiparous women.¹⁰

Even in the absence of episiotomy, from 35%¹⁵ to 75%^16,17 of women suffer a perineal trauma while giving birth. Risk factors include nulliparity,^17,18 use of stirrups for delivery,¹⁹ second stage of labor of at least 1 hour,^6,18,20-22 shoulder dystocia,²¹ forceps delivery,^18,19,22-24 and excessive birth weight.^20,21,23

Very few studies have assessed whether perineal trauma experienced during a first delivery is a risk factor for spontaneous tears at the next delivery. Observations from the West Berkshire randomized perineal management trial²⁵ suggested that this could be the case, even though the results were not statistically significant. Of the 1000 women enrolled in that trial, 67% completed a questionnaire 3 years later, and 40% of the respondents had a second delivery in the interval. The women assigned to the “liberal” group (instruction to try to prevent a tear) tended to carry a higher risk of perineal tears at the next delivery than those assigned to the “restricted” group (to restrict episiotomy to fetal indications) [46% and 40%, respectively; P=0.3]. Two recent studies^26,27 have reported an increased risk of severe perineal lacerations (third- and fourth-degree tears) in women who sustained such lacerations at their previous delivery, but these studies did not provide data on the whole range of perineal trauma.

Our objective for this retrospective cohort study was to assess whether the presence and severity of perineal trauma (defined as a spontaneous tear or an episiotomy with and without extension) at the first delivery are related to the risk of spontaneous perineal tears of the second degree or more in women who subsequently deliver vaginally without an episiotomy.

Methods

We included women who gave birth to their first and second baby at Saint-Sacrement Hospital of the Centre hospitalier affilié universitaire de Québec, Canada, between January 1, 1985, and December 31, 1994. Those who had a cesarean delivery, a multiple birth, or a stillbirth at either the first or second delivery were excluded, as were those who had an episiotomy at the second delivery.

We abstracted the data from the computerized database maintained by the Department of Obstetrics since 1985. The delivery physician routinely recorded data about labor and delivery on a standard form after the delivery. The attending physician indicated on the standard form whether the woman had no tear, a first-degree tear (limited to the fourchet, the perineal skin, and the vaginal mucosa), a second-degree tear (extending to perineal muscles but saving the anal sphincter), a third-degree tear (involving muscles of the central nucleus and the anal sphincter with anal mucosa remaining intact), a fourth-degree tear (complete rupture of the anal sphincter through the mucosa),²⁸ or an episiotomy (with or without a third- or fourth-degree extension). Except for some first-degree tears, all other trauma required a surgical repair. The decision to cut an episiotomy was left to the discretion of the physician. The standard form also included information on factors potentially related to perineal tears, such as maternal age, epidural use, use of forceps or vacuum, shoulder dystocia, fetal presentation, gestational age (based on last menstrual period or on ultrasound dating, if the 2 estimations differ by more than 10 days), birth weight, head circumference of the newborn, and the training (obstetrics and gynecology or general or family medicine) and identity of the birth attendant. Data from these forms were computerized periodically by one obstetrician (J.J.P.). Incomplete or inconsistent data were checked using the medical records.

Women who gave birth with an intact perineum or a first-degree tear at the first delivery made up the “unexposed” group. Those who experienced a perineal trauma (an episiotomy or a spontaneous perineal tear of the second degree or higher) at the first delivery were considered “exposed.” Exposure was also categorized according to the severity of the trauma: second-degree spontaneous tear, episiotomy without extension, third- or fourth-degree spontaneous tear, and third- or fourth-degree extension of an episiotomy. All episiotomies were median. The dependent variable was defined as the presence of a second-, third- or fourth-degree spontaneous tear at the second delivery (indicated yes or no).

The association between perineal tears at the second delivery and a history of perineal trauma was primarily measured by the relative risk (RR). The precision of the estimate was given by the 95% confidence interval (95% CI). We also performed unconditional logistic regression to evaluate the influence of potential confounders on the association.²⁹ Unadjusted and adjusted odds ratios (ORs) were obtained. Because the outcome was relatively frequent, the OR overestimated the RR. Trends in proportions were tested with the c2 test for trend.³⁰ Comparisons of proportions were based on Pearson c2 tests.

Results

Of the 3769 women who had their first and second deliveries in the same hospital during the study period, we excluded 579 (15.4%) who had a cesarean delivery, 66 who had a multiple pregnancy, and 31 who had a stillbirth. We also excluded 1198 women who underwent an episiotomy at their second delivery. Among the 1895 secondiparous women left in the analysis, 462 (24.4%) had an intact perineum or a first-degree tear at the first delivery, 333 (17.6%) had a spontaneous second-degree (302) or third- or fourth-degree tear (31); and 1100 (58.0%) had an episiotomy without (911) or with (189) a third- or fourth-degree extension. At the second delivery 1196 (63.1%) delivered with an intact perineum or had a first-degree tear, while 699 (36.9%) had a tear of the second (686) or third or fourth degree (13).

Risk factors for spontaneous perineal tears at the second delivery are presented in Table 1. The unadjusted risk increased with maternal age, gestational age at delivery, birth weight, and fetal head circumference (all tests for trend, P≤.003). The risk was also higher in nonvertex than vertex presentations and in vacuum- or forceps-assisted deliveries than in spontaneous vaginal deliveries. Epidural analgesia, shoulder dystocia, and the training, experience (years since graduation), and identity (data not shown) of the birth attendant were not related to the risk of spontaneous tears in secondiparous women.

Among women who previously gave birth with an intact perineum or a first-degree laceration, 13.4% had a spontaneous tear of the second degree or more at the next delivery Table 2. The risk did not differ whether women had a history of intact perineum (13.0%) or of first-degree tear (14.1% [c2=0.1, P=.7]). In contrast, among women previously exposed to perineal trauma (episiotomy; second-, third-, or fourth-degree tear) 44.5% underwent a spontaneous tear of the second degree or higher at the subsequent delivery. Thus, the overall risk of spontaneous tears (second, third, or fourth degree) was 3.3 times higher in women with a history of perineal trauma at the first delivery than in those without (RR=3.3; 95% CI, 2.6-4.2). The risk of perineal tears at the second delivery increased with the severity of the trauma at the first delivery (test for trend, P <.001). The risk was higher in women with a previous episiotomy without extension (44.8%) than in women with a spontaneous second-degree laceration (36.1%). Severe lacerations at the first delivery yielded the highest risk (54.5%), but the risk was similar whether previous severe lacerations were spontaneous (54.8%) or secondary to an extension of episiotomy (54.5%). Among the 220 women who suffered a third- or fourth-degree perineal tear at their first birth, 2 (0.9%) were delivered with such a tear at their second birth, while among the 1675 who did not suffer a third- or fourth-degree perineal tear at their first delivery, 11 (0.7 %) were delivered with such trauma (RR=1.4; 95% CI, 0.3-6.3).

To verify that the risk factors shown in Table 1 did not confound the associations, we carried out an unconditional logistic regression analysis with simultaneous adjustment for maternal age, birth weight, length of gestation, head circumference, fetal presentation, and mode of delivery. This analysis yielded an adjusted OR of 5.3 (95% CI, 3.9-7.1) for the relation of a history of perineal trauma at the first delivery and the risk of perineal tears (second-, third-, or fourth-degree tears) at the second delivery. As the adjusted OR is similar to the unadjusted OR (5.2; 95% CI, 3.9-6.9), this indicates that the risk factors entered into the model did not confound the association. When the severity of perineal trauma at the first delivery was categorized as in Table 2, the regression analysis again suggested there was no confounding (data not shown).

To estimate the influence of the exclusion of the 1198 women who had an episiotomy at their second delivery, we reanalyzed our data to include these women. At their first delivery: 65 of them had no tear or a first-degree tear; 70 had a second-degree spontaneous tear; 13 had a spontaneous third- or fourth-degree tear; 789 had an episiotomy without extension; and 261 had a third- or fourth-degree extension of an episiotomy. The risk of trauma at the second delivery in the 3093 women was 24.1% for those without a history of perineal trauma and 69% for those who had (RR=2.9; 95% CI, 2.5-3.3). Also, spontaneous tears at the second delivery were 2.1 times (95% CI, 1.7-2.7) more frequent in women who had a previous perineal trauma.

Discussion

Our results indicate that the risk of spontaneous perineal lacerations (second-, third- or fourth-degree tears) at the second delivery increases with the presence and severity of perineal trauma at the previous delivery. To our knowledge this study is the first to demonstrate that association.

An increased risk of severe perineal lacerations (third- and fourth-degree tears) has been reported in women who sustained such lacerations at their previous delivery in studies by Payne and colleagues (unadjusted OR=3.4; 95% CI, 1.8-6.4)²⁶ and by Peleg and coworkers (OR=2.5; 95% CI, 1.8-3.4).²⁷ In these studies, many women gave birth with a median episiotomy, a known risk factor for severe perineal tears. However, the association persisted after adjustment for episiotomy²⁶ or in the subset of spontaneous births (RR=6.5; 95% CI, 2.0-21.2).²⁷ In our study, a similar trend was observed but was not statistically significant.

Our results support the view that the prevention of perineal trauma in first deliveries could benefit women in subsequent deliveries. Prenatal perineal massage constitutes a simple and valuable approach for doing so.³¹ Recent randomized controlled trials indicate that perineal massage during pregnancy increases the likelihood for primiparous women of delivering with an intact perineum.^32,33 Avoiding episiotomy, in addition to increasing the rate of intact perineum reduces the severity of perineal trauma. In a previous study¹⁰ we reported a 3-fold increase of third- and fourth-degree perineal tears associated with median episiotomy in primiparous women. In that study, while the episiotomy rate declined from 77.7% in 1985-1987 to 56.2% in 1991-1993, the rate of severe perineal lacerations fell from 17.2% to 12.6% during the same period. Finally, restricting forceps birth also enhances perineal integrity.³¹

Limitations

We studied a large cohort of women who delivered twice at the same hospital. The exclusion of women who had their second delivery in a different hospital raises the possibility of a selection bias. It was not possible to estimate the number of these exclusions. This phenomenon, however, is not frequent, and we see no reason that women who had a history of perineal trauma and changed hospitals would be more or less likely to have a perineal tear at their second delivery than women included in the analysis.

Our study was restricted to women who did not have an episiotomy at the second delivery. We did this because we were interested in estimating the likelihood of a spontaneous tear, which cannot be determined in women undergoing an episiotomy. The decision to undertake an episiotomy was at the discretion of the physician, and policies regarding the use of episiotomy varied between physicians as well as over the study period. Some physicians may have been more likely to undertake an episiotomy if they noticed the presence of a perineal scar. If this were the case, the exclusion of women who underwent an episiotomy at the second delivery could have resulted in an underestimation of the strength of the association between perineal trauma at the first delivery and spontaneous tears at the second delivery. However, if the reasons women had an episiotomy at their second delivery were independent of the state of the perineum at the first delivery, the influence on the association is unpredictable and would depend on underlying unknown risk of spontaneous tear in women with and without episiotomy. Reanalyzing our data to include the women who had an episiotomy at their second delivery showed that the strength of the association decreases, but history of perineal trauma remains a clinically and statistically significant risk factor for such trauma at the second delivery.

Our analysis took into account most of the variables known to be related to the risk of perineal trauma. However, we did not have information on the duration of the second stage, the use of oxytocin in the second stage of labor, and the delivery position. These variables would confound our results if they were related to a history of perineal trauma and independent risk factors for perineal tears in subsequent deliveries. Confounding by these variables cannot be eliminated but appears unlikely, since stronger risk factors such as excessive birth weight and shoulder dystocia did not introduce any confounding in our data. Another possible explanation for the observed association is that some perinea might be inherently more prone to tearing than others, possibly because of genetic factors.

Conclusions

Our study shows that the risk of spontaneous perineal tears at the second delivery increases with the presence and the severity of perineal trauma at the first delivery. These results support arguments for the prevention of perineal trauma at the first delivery and the selective use of episiotomy.

Acknowledgements

Dr Marcoux holds a National Health Research Scholarship from Health Canada.

Related resources

FOR PATIENTS:

• ParentsPlace.com—Perineal Massage: Your How-to Guidehttp://www.parentsplace.com/pregnancy/labor/qa/0,3105,13778,00.html
• Childbirth.org—Perineal Massagehttp://www.childbirth.org/articles/massage.html

FOR FAMILY PHYSICIANS:

• Obstetric Myths Versus Research Realitieshttp://www.efn.org/~djz/birth/obmyth/epis.html
• Wooley RJ. Benefits and risks of episiotomy: A review of the English-language literature since 1980 http://www.gentlebirth.org/format/woolley.html(the best one on episotomy)
• Carroli G, Belizan J. Episiotomy for vaginal birth (Cochrane Review)http://www.update-software.com/abstracts/ab000081.htm (Only the abstract is available free.)

Women frequently incur perineal trauma at delivery. Such trauma is associated with perineal pain that may still be present 3 months postpartum,^1-4 dyspareunia,^1,2 perineal infection,^4,5 and following severe lacerations, fistula and incontinence of flatus and feces.^6,7 Episiotomy accounts for a large proportion of perineal trauma. Wide variations exist in the use of episiotomy according to country,⁵ hospital,⁸ or birth attendant.^1,9-12 There is no evidence that it is effective in preventing severe lacerations^13,14 and pelvic floor relaxation^1,7,13 or that recovery is more rapid and morbidity less than that following spontaneous tears.^5,7 Also, median episiotomy increases the risk of severe perineal lacerations,¹⁴ particularly in primiparous women.¹⁰

Even in the absence of episiotomy, from 35%¹⁵ to 75%^16,17 of women suffer a perineal trauma while giving birth. Risk factors include nulliparity,^17,18 use of stirrups for delivery,¹⁹ second stage of labor of at least 1 hour,^6,18,20-22 shoulder dystocia,²¹ forceps delivery,^18,19,22-24 and excessive birth weight.^20,21,23

Very few studies have assessed whether perineal trauma experienced during a first delivery is a risk factor for spontaneous tears at the next delivery. Observations from the West Berkshire randomized perineal management trial²⁵ suggested that this could be the case, even though the results were not statistically significant. Of the 1000 women enrolled in that trial, 67% completed a questionnaire 3 years later, and 40% of the respondents had a second delivery in the interval. The women assigned to the “liberal” group (instruction to try to prevent a tear) tended to carry a higher risk of perineal tears at the next delivery than those assigned to the “restricted” group (to restrict episiotomy to fetal indications) [46% and 40%, respectively; P=0.3]. Two recent studies^26,27 have reported an increased risk of severe perineal lacerations (third- and fourth-degree tears) in women who sustained such lacerations at their previous delivery, but these studies did not provide data on the whole range of perineal trauma.

Our objective for this retrospective cohort study was to assess whether the presence and severity of perineal trauma (defined as a spontaneous tear or an episiotomy with and without extension) at the first delivery are related to the risk of spontaneous perineal tears of the second degree or more in women who subsequently deliver vaginally without an episiotomy.

Methods

We included women who gave birth to their first and second baby at Saint-Sacrement Hospital of the Centre hospitalier affilié universitaire de Québec, Canada, between January 1, 1985, and December 31, 1994. Those who had a cesarean delivery, a multiple birth, or a stillbirth at either the first or second delivery were excluded, as were those who had an episiotomy at the second delivery.

We abstracted the data from the computerized database maintained by the Department of Obstetrics since 1985. The delivery physician routinely recorded data about labor and delivery on a standard form after the delivery. The attending physician indicated on the standard form whether the woman had no tear, a first-degree tear (limited to the fourchet, the perineal skin, and the vaginal mucosa), a second-degree tear (extending to perineal muscles but saving the anal sphincter), a third-degree tear (involving muscles of the central nucleus and the anal sphincter with anal mucosa remaining intact), a fourth-degree tear (complete rupture of the anal sphincter through the mucosa),²⁸ or an episiotomy (with or without a third- or fourth-degree extension). Except for some first-degree tears, all other trauma required a surgical repair. The decision to cut an episiotomy was left to the discretion of the physician. The standard form also included information on factors potentially related to perineal tears, such as maternal age, epidural use, use of forceps or vacuum, shoulder dystocia, fetal presentation, gestational age (based on last menstrual period or on ultrasound dating, if the 2 estimations differ by more than 10 days), birth weight, head circumference of the newborn, and the training (obstetrics and gynecology or general or family medicine) and identity of the birth attendant. Data from these forms were computerized periodically by one obstetrician (J.J.P.). Incomplete or inconsistent data were checked using the medical records.

Women who gave birth with an intact perineum or a first-degree tear at the first delivery made up the “unexposed” group. Those who experienced a perineal trauma (an episiotomy or a spontaneous perineal tear of the second degree or higher) at the first delivery were considered “exposed.” Exposure was also categorized according to the severity of the trauma: second-degree spontaneous tear, episiotomy without extension, third- or fourth-degree spontaneous tear, and third- or fourth-degree extension of an episiotomy. All episiotomies were median. The dependent variable was defined as the presence of a second-, third- or fourth-degree spontaneous tear at the second delivery (indicated yes or no).

The association between perineal tears at the second delivery and a history of perineal trauma was primarily measured by the relative risk (RR). The precision of the estimate was given by the 95% confidence interval (95% CI). We also performed unconditional logistic regression to evaluate the influence of potential confounders on the association.²⁹ Unadjusted and adjusted odds ratios (ORs) were obtained. Because the outcome was relatively frequent, the OR overestimated the RR. Trends in proportions were tested with the c2 test for trend.³⁰ Comparisons of proportions were based on Pearson c2 tests.

Results

Of the 3769 women who had their first and second deliveries in the same hospital during the study period, we excluded 579 (15.4%) who had a cesarean delivery, 66 who had a multiple pregnancy, and 31 who had a stillbirth. We also excluded 1198 women who underwent an episiotomy at their second delivery. Among the 1895 secondiparous women left in the analysis, 462 (24.4%) had an intact perineum or a first-degree tear at the first delivery, 333 (17.6%) had a spontaneous second-degree (302) or third- or fourth-degree tear (31); and 1100 (58.0%) had an episiotomy without (911) or with (189) a third- or fourth-degree extension. At the second delivery 1196 (63.1%) delivered with an intact perineum or had a first-degree tear, while 699 (36.9%) had a tear of the second (686) or third or fourth degree (13).

Risk factors for spontaneous perineal tears at the second delivery are presented in Table 1. The unadjusted risk increased with maternal age, gestational age at delivery, birth weight, and fetal head circumference (all tests for trend, P≤.003). The risk was also higher in nonvertex than vertex presentations and in vacuum- or forceps-assisted deliveries than in spontaneous vaginal deliveries. Epidural analgesia, shoulder dystocia, and the training, experience (years since graduation), and identity (data not shown) of the birth attendant were not related to the risk of spontaneous tears in secondiparous women.

Among women who previously gave birth with an intact perineum or a first-degree laceration, 13.4% had a spontaneous tear of the second degree or more at the next delivery Table 2. The risk did not differ whether women had a history of intact perineum (13.0%) or of first-degree tear (14.1% [c2=0.1, P=.7]). In contrast, among women previously exposed to perineal trauma (episiotomy; second-, third-, or fourth-degree tear) 44.5% underwent a spontaneous tear of the second degree or higher at the subsequent delivery. Thus, the overall risk of spontaneous tears (second, third, or fourth degree) was 3.3 times higher in women with a history of perineal trauma at the first delivery than in those without (RR=3.3; 95% CI, 2.6-4.2). The risk of perineal tears at the second delivery increased with the severity of the trauma at the first delivery (test for trend, P <.001). The risk was higher in women with a previous episiotomy without extension (44.8%) than in women with a spontaneous second-degree laceration (36.1%). Severe lacerations at the first delivery yielded the highest risk (54.5%), but the risk was similar whether previous severe lacerations were spontaneous (54.8%) or secondary to an extension of episiotomy (54.5%). Among the 220 women who suffered a third- or fourth-degree perineal tear at their first birth, 2 (0.9%) were delivered with such a tear at their second birth, while among the 1675 who did not suffer a third- or fourth-degree perineal tear at their first delivery, 11 (0.7 %) were delivered with such trauma (RR=1.4; 95% CI, 0.3-6.3).

To verify that the risk factors shown in Table 1 did not confound the associations, we carried out an unconditional logistic regression analysis with simultaneous adjustment for maternal age, birth weight, length of gestation, head circumference, fetal presentation, and mode of delivery. This analysis yielded an adjusted OR of 5.3 (95% CI, 3.9-7.1) for the relation of a history of perineal trauma at the first delivery and the risk of perineal tears (second-, third-, or fourth-degree tears) at the second delivery. As the adjusted OR is similar to the unadjusted OR (5.2; 95% CI, 3.9-6.9), this indicates that the risk factors entered into the model did not confound the association. When the severity of perineal trauma at the first delivery was categorized as in Table 2, the regression analysis again suggested there was no confounding (data not shown).

To estimate the influence of the exclusion of the 1198 women who had an episiotomy at their second delivery, we reanalyzed our data to include these women. At their first delivery: 65 of them had no tear or a first-degree tear; 70 had a second-degree spontaneous tear; 13 had a spontaneous third- or fourth-degree tear; 789 had an episiotomy without extension; and 261 had a third- or fourth-degree extension of an episiotomy. The risk of trauma at the second delivery in the 3093 women was 24.1% for those without a history of perineal trauma and 69% for those who had (RR=2.9; 95% CI, 2.5-3.3). Also, spontaneous tears at the second delivery were 2.1 times (95% CI, 1.7-2.7) more frequent in women who had a previous perineal trauma.

Discussion

Our results indicate that the risk of spontaneous perineal lacerations (second-, third- or fourth-degree tears) at the second delivery increases with the presence and severity of perineal trauma at the previous delivery. To our knowledge this study is the first to demonstrate that association.

An increased risk of severe perineal lacerations (third- and fourth-degree tears) has been reported in women who sustained such lacerations at their previous delivery in studies by Payne and colleagues (unadjusted OR=3.4; 95% CI, 1.8-6.4)²⁶ and by Peleg and coworkers (OR=2.5; 95% CI, 1.8-3.4).²⁷ In these studies, many women gave birth with a median episiotomy, a known risk factor for severe perineal tears. However, the association persisted after adjustment for episiotomy²⁶ or in the subset of spontaneous births (RR=6.5; 95% CI, 2.0-21.2).²⁷ In our study, a similar trend was observed but was not statistically significant.

Our results support the view that the prevention of perineal trauma in first deliveries could benefit women in subsequent deliveries. Prenatal perineal massage constitutes a simple and valuable approach for doing so.³¹ Recent randomized controlled trials indicate that perineal massage during pregnancy increases the likelihood for primiparous women of delivering with an intact perineum.^32,33 Avoiding episiotomy, in addition to increasing the rate of intact perineum reduces the severity of perineal trauma. In a previous study¹⁰ we reported a 3-fold increase of third- and fourth-degree perineal tears associated with median episiotomy in primiparous women. In that study, while the episiotomy rate declined from 77.7% in 1985-1987 to 56.2% in 1991-1993, the rate of severe perineal lacerations fell from 17.2% to 12.6% during the same period. Finally, restricting forceps birth also enhances perineal integrity.³¹

Limitations

We studied a large cohort of women who delivered twice at the same hospital. The exclusion of women who had their second delivery in a different hospital raises the possibility of a selection bias. It was not possible to estimate the number of these exclusions. This phenomenon, however, is not frequent, and we see no reason that women who had a history of perineal trauma and changed hospitals would be more or less likely to have a perineal tear at their second delivery than women included in the analysis.

Our study was restricted to women who did not have an episiotomy at the second delivery. We did this because we were interested in estimating the likelihood of a spontaneous tear, which cannot be determined in women undergoing an episiotomy. The decision to undertake an episiotomy was at the discretion of the physician, and policies regarding the use of episiotomy varied between physicians as well as over the study period. Some physicians may have been more likely to undertake an episiotomy if they noticed the presence of a perineal scar. If this were the case, the exclusion of women who underwent an episiotomy at the second delivery could have resulted in an underestimation of the strength of the association between perineal trauma at the first delivery and spontaneous tears at the second delivery. However, if the reasons women had an episiotomy at their second delivery were independent of the state of the perineum at the first delivery, the influence on the association is unpredictable and would depend on underlying unknown risk of spontaneous tear in women with and without episiotomy. Reanalyzing our data to include the women who had an episiotomy at their second delivery showed that the strength of the association decreases, but history of perineal trauma remains a clinically and statistically significant risk factor for such trauma at the second delivery.

Our analysis took into account most of the variables known to be related to the risk of perineal trauma. However, we did not have information on the duration of the second stage, the use of oxytocin in the second stage of labor, and the delivery position. These variables would confound our results if they were related to a history of perineal trauma and independent risk factors for perineal tears in subsequent deliveries. Confounding by these variables cannot be eliminated but appears unlikely, since stronger risk factors such as excessive birth weight and shoulder dystocia did not introduce any confounding in our data. Another possible explanation for the observed association is that some perinea might be inherently more prone to tearing than others, possibly because of genetic factors.

Conclusions

Our study shows that the risk of spontaneous perineal tears at the second delivery increases with the presence and the severity of perineal trauma at the first delivery. These results support arguments for the prevention of perineal trauma at the first delivery and the selective use of episiotomy.

Acknowledgements

Dr Marcoux holds a National Health Research Scholarship from Health Canada.

Related resources

FOR PATIENTS:

• ParentsPlace.com—Perineal Massage: Your How-to Guidehttp://www.parentsplace.com/pregnancy/labor/qa/0,3105,13778,00.html
• Childbirth.org—Perineal Massagehttp://www.childbirth.org/articles/massage.html

FOR FAMILY PHYSICIANS:

• Obstetric Myths Versus Research Realitieshttp://www.efn.org/~djz/birth/obmyth/epis.html
• Wooley RJ. Benefits and risks of episiotomy: A review of the English-language literature since 1980 http://www.gentlebirth.org/format/woolley.html(the best one on episotomy)
• Carroli G, Belizan J. Episiotomy for vaginal birth (Cochrane Review)http://www.update-software.com/abstracts/ab000081.htm (Only the abstract is available free.)

Women frequently incur perineal trauma at delivery. Such trauma is associated with perineal pain that may still be present 3 months postpartum,^1-4 dyspareunia,^1,2 perineal infection,^4,5 and following severe lacerations, fistula and incontinence of flatus and feces.^6,7 Episiotomy accounts for a large proportion of perineal trauma. Wide variations exist in the use of episiotomy according to country,⁵ hospital,⁸ or birth attendant.^1,9-12 There is no evidence that it is effective in preventing severe lacerations^13,14 and pelvic floor relaxation^1,7,13 or that recovery is more rapid and morbidity less than that following spontaneous tears.^5,7 Also, median episiotomy increases the risk of severe perineal lacerations,¹⁴ particularly in primiparous women.¹⁰

Even in the absence of episiotomy, from 35%¹⁵ to 75%^16,17 of women suffer a perineal trauma while giving birth. Risk factors include nulliparity,^17,18 use of stirrups for delivery,¹⁹ second stage of labor of at least 1 hour,^6,18,20-22 shoulder dystocia,²¹ forceps delivery,^18,19,22-24 and excessive birth weight.^20,21,23

Very few studies have assessed whether perineal trauma experienced during a first delivery is a risk factor for spontaneous tears at the next delivery. Observations from the West Berkshire randomized perineal management trial²⁵ suggested that this could be the case, even though the results were not statistically significant. Of the 1000 women enrolled in that trial, 67% completed a questionnaire 3 years later, and 40% of the respondents had a second delivery in the interval. The women assigned to the “liberal” group (instruction to try to prevent a tear) tended to carry a higher risk of perineal tears at the next delivery than those assigned to the “restricted” group (to restrict episiotomy to fetal indications) [46% and 40%, respectively; P=0.3]. Two recent studies^26,27 have reported an increased risk of severe perineal lacerations (third- and fourth-degree tears) in women who sustained such lacerations at their previous delivery, but these studies did not provide data on the whole range of perineal trauma.

Our objective for this retrospective cohort study was to assess whether the presence and severity of perineal trauma (defined as a spontaneous tear or an episiotomy with and without extension) at the first delivery are related to the risk of spontaneous perineal tears of the second degree or more in women who subsequently deliver vaginally without an episiotomy.

Methods

We included women who gave birth to their first and second baby at Saint-Sacrement Hospital of the Centre hospitalier affilié universitaire de Québec, Canada, between January 1, 1985, and December 31, 1994. Those who had a cesarean delivery, a multiple birth, or a stillbirth at either the first or second delivery were excluded, as were those who had an episiotomy at the second delivery.

We abstracted the data from the computerized database maintained by the Department of Obstetrics since 1985. The delivery physician routinely recorded data about labor and delivery on a standard form after the delivery. The attending physician indicated on the standard form whether the woman had no tear, a first-degree tear (limited to the fourchet, the perineal skin, and the vaginal mucosa), a second-degree tear (extending to perineal muscles but saving the anal sphincter), a third-degree tear (involving muscles of the central nucleus and the anal sphincter with anal mucosa remaining intact), a fourth-degree tear (complete rupture of the anal sphincter through the mucosa),²⁸ or an episiotomy (with or without a third- or fourth-degree extension). Except for some first-degree tears, all other trauma required a surgical repair. The decision to cut an episiotomy was left to the discretion of the physician. The standard form also included information on factors potentially related to perineal tears, such as maternal age, epidural use, use of forceps or vacuum, shoulder dystocia, fetal presentation, gestational age (based on last menstrual period or on ultrasound dating, if the 2 estimations differ by more than 10 days), birth weight, head circumference of the newborn, and the training (obstetrics and gynecology or general or family medicine) and identity of the birth attendant. Data from these forms were computerized periodically by one obstetrician (J.J.P.). Incomplete or inconsistent data were checked using the medical records.

Women who gave birth with an intact perineum or a first-degree tear at the first delivery made up the “unexposed” group. Those who experienced a perineal trauma (an episiotomy or a spontaneous perineal tear of the second degree or higher) at the first delivery were considered “exposed.” Exposure was also categorized according to the severity of the trauma: second-degree spontaneous tear, episiotomy without extension, third- or fourth-degree spontaneous tear, and third- or fourth-degree extension of an episiotomy. All episiotomies were median. The dependent variable was defined as the presence of a second-, third- or fourth-degree spontaneous tear at the second delivery (indicated yes or no).

The association between perineal tears at the second delivery and a history of perineal trauma was primarily measured by the relative risk (RR). The precision of the estimate was given by the 95% confidence interval (95% CI). We also performed unconditional logistic regression to evaluate the influence of potential confounders on the association.²⁹ Unadjusted and adjusted odds ratios (ORs) were obtained. Because the outcome was relatively frequent, the OR overestimated the RR. Trends in proportions were tested with the c2 test for trend.³⁰ Comparisons of proportions were based on Pearson c2 tests.

Results

Of the 3769 women who had their first and second deliveries in the same hospital during the study period, we excluded 579 (15.4%) who had a cesarean delivery, 66 who had a multiple pregnancy, and 31 who had a stillbirth. We also excluded 1198 women who underwent an episiotomy at their second delivery. Among the 1895 secondiparous women left in the analysis, 462 (24.4%) had an intact perineum or a first-degree tear at the first delivery, 333 (17.6%) had a spontaneous second-degree (302) or third- or fourth-degree tear (31); and 1100 (58.0%) had an episiotomy without (911) or with (189) a third- or fourth-degree extension. At the second delivery 1196 (63.1%) delivered with an intact perineum or had a first-degree tear, while 699 (36.9%) had a tear of the second (686) or third or fourth degree (13).

Risk factors for spontaneous perineal tears at the second delivery are presented in Table 1. The unadjusted risk increased with maternal age, gestational age at delivery, birth weight, and fetal head circumference (all tests for trend, P≤.003). The risk was also higher in nonvertex than vertex presentations and in vacuum- or forceps-assisted deliveries than in spontaneous vaginal deliveries. Epidural analgesia, shoulder dystocia, and the training, experience (years since graduation), and identity (data not shown) of the birth attendant were not related to the risk of spontaneous tears in secondiparous women.

Among women who previously gave birth with an intact perineum or a first-degree laceration, 13.4% had a spontaneous tear of the second degree or more at the next delivery Table 2. The risk did not differ whether women had a history of intact perineum (13.0%) or of first-degree tear (14.1% [c2=0.1, P=.7]). In contrast, among women previously exposed to perineal trauma (episiotomy; second-, third-, or fourth-degree tear) 44.5% underwent a spontaneous tear of the second degree or higher at the subsequent delivery. Thus, the overall risk of spontaneous tears (second, third, or fourth degree) was 3.3 times higher in women with a history of perineal trauma at the first delivery than in those without (RR=3.3; 95% CI, 2.6-4.2). The risk of perineal tears at the second delivery increased with the severity of the trauma at the first delivery (test for trend, P <.001). The risk was higher in women with a previous episiotomy without extension (44.8%) than in women with a spontaneous second-degree laceration (36.1%). Severe lacerations at the first delivery yielded the highest risk (54.5%), but the risk was similar whether previous severe lacerations were spontaneous (54.8%) or secondary to an extension of episiotomy (54.5%). Among the 220 women who suffered a third- or fourth-degree perineal tear at their first birth, 2 (0.9%) were delivered with such a tear at their second birth, while among the 1675 who did not suffer a third- or fourth-degree perineal tear at their first delivery, 11 (0.7 %) were delivered with such trauma (RR=1.4; 95% CI, 0.3-6.3).

To verify that the risk factors shown in Table 1 did not confound the associations, we carried out an unconditional logistic regression analysis with simultaneous adjustment for maternal age, birth weight, length of gestation, head circumference, fetal presentation, and mode of delivery. This analysis yielded an adjusted OR of 5.3 (95% CI, 3.9-7.1) for the relation of a history of perineal trauma at the first delivery and the risk of perineal tears (second-, third-, or fourth-degree tears) at the second delivery. As the adjusted OR is similar to the unadjusted OR (5.2; 95% CI, 3.9-6.9), this indicates that the risk factors entered into the model did not confound the association. When the severity of perineal trauma at the first delivery was categorized as in Table 2, the regression analysis again suggested there was no confounding (data not shown).

To estimate the influence of the exclusion of the 1198 women who had an episiotomy at their second delivery, we reanalyzed our data to include these women. At their first delivery: 65 of them had no tear or a first-degree tear; 70 had a second-degree spontaneous tear; 13 had a spontaneous third- or fourth-degree tear; 789 had an episiotomy without extension; and 261 had a third- or fourth-degree extension of an episiotomy. The risk of trauma at the second delivery in the 3093 women was 24.1% for those without a history of perineal trauma and 69% for those who had (RR=2.9; 95% CI, 2.5-3.3). Also, spontaneous tears at the second delivery were 2.1 times (95% CI, 1.7-2.7) more frequent in women who had a previous perineal trauma.

Discussion

Our results indicate that the risk of spontaneous perineal lacerations (second-, third- or fourth-degree tears) at the second delivery increases with the presence and severity of perineal trauma at the previous delivery. To our knowledge this study is the first to demonstrate that association.

An increased risk of severe perineal lacerations (third- and fourth-degree tears) has been reported in women who sustained such lacerations at their previous delivery in studies by Payne and colleagues (unadjusted OR=3.4; 95% CI, 1.8-6.4)²⁶ and by Peleg and coworkers (OR=2.5; 95% CI, 1.8-3.4).²⁷ In these studies, many women gave birth with a median episiotomy, a known risk factor for severe perineal tears. However, the association persisted after adjustment for episiotomy²⁶ or in the subset of spontaneous births (RR=6.5; 95% CI, 2.0-21.2).²⁷ In our study, a similar trend was observed but was not statistically significant.

Our results support the view that the prevention of perineal trauma in first deliveries could benefit women in subsequent deliveries. Prenatal perineal massage constitutes a simple and valuable approach for doing so.³¹ Recent randomized controlled trials indicate that perineal massage during pregnancy increases the likelihood for primiparous women of delivering with an intact perineum.^32,33 Avoiding episiotomy, in addition to increasing the rate of intact perineum reduces the severity of perineal trauma. In a previous study¹⁰ we reported a 3-fold increase of third- and fourth-degree perineal tears associated with median episiotomy in primiparous women. In that study, while the episiotomy rate declined from 77.7% in 1985-1987 to 56.2% in 1991-1993, the rate of severe perineal lacerations fell from 17.2% to 12.6% during the same period. Finally, restricting forceps birth also enhances perineal integrity.³¹

Limitations

We studied a large cohort of women who delivered twice at the same hospital. The exclusion of women who had their second delivery in a different hospital raises the possibility of a selection bias. It was not possible to estimate the number of these exclusions. This phenomenon, however, is not frequent, and we see no reason that women who had a history of perineal trauma and changed hospitals would be more or less likely to have a perineal tear at their second delivery than women included in the analysis.

Our study was restricted to women who did not have an episiotomy at the second delivery. We did this because we were interested in estimating the likelihood of a spontaneous tear, which cannot be determined in women undergoing an episiotomy. The decision to undertake an episiotomy was at the discretion of the physician, and policies regarding the use of episiotomy varied between physicians as well as over the study period. Some physicians may have been more likely to undertake an episiotomy if they noticed the presence of a perineal scar. If this were the case, the exclusion of women who underwent an episiotomy at the second delivery could have resulted in an underestimation of the strength of the association between perineal trauma at the first delivery and spontaneous tears at the second delivery. However, if the reasons women had an episiotomy at their second delivery were independent of the state of the perineum at the first delivery, the influence on the association is unpredictable and would depend on underlying unknown risk of spontaneous tear in women with and without episiotomy. Reanalyzing our data to include the women who had an episiotomy at their second delivery showed that the strength of the association decreases, but history of perineal trauma remains a clinically and statistically significant risk factor for such trauma at the second delivery.

Our analysis took into account most of the variables known to be related to the risk of perineal trauma. However, we did not have information on the duration of the second stage, the use of oxytocin in the second stage of labor, and the delivery position. These variables would confound our results if they were related to a history of perineal trauma and independent risk factors for perineal tears in subsequent deliveries. Confounding by these variables cannot be eliminated but appears unlikely, since stronger risk factors such as excessive birth weight and shoulder dystocia did not introduce any confounding in our data. Another possible explanation for the observed association is that some perinea might be inherently more prone to tearing than others, possibly because of genetic factors.

Conclusions

Our study shows that the risk of spontaneous perineal tears at the second delivery increases with the presence and the severity of perineal trauma at the first delivery. These results support arguments for the prevention of perineal trauma at the first delivery and the selective use of episiotomy.

Acknowledgements

Dr Marcoux holds a National Health Research Scholarship from Health Canada.

Related resources

FOR PATIENTS:

• ParentsPlace.com—Perineal Massage: Your How-to Guidehttp://www.parentsplace.com/pregnancy/labor/qa/0,3105,13778,00.html
• Childbirth.org—Perineal Massagehttp://www.childbirth.org/articles/massage.html

FOR FAMILY PHYSICIANS:

• Obstetric Myths Versus Research Realitieshttp://www.efn.org/~djz/birth/obmyth/epis.html
• Wooley RJ. Benefits and risks of episiotomy: A review of the English-language literature since 1980 http://www.gentlebirth.org/format/woolley.html(the best one on episotomy)
• Carroli G, Belizan J. Episiotomy for vaginal birth (Cochrane Review)http://www.update-software.com/abstracts/ab000081.htm (Only the abstract is available free.)