Katariina Laine

Changing incidence of anal sphincter tears in four Nordic countries through the last decades

OBJECTIVES Anal sphincter rupture is a serious complication of a vaginal delivery. A considerable number of women suffer permanent anal incontinence after this type of injury. The incidence of sphincter tears is believed to have increased over several decades in Denmark, Norway, Sweden and Finland, but there seem to be significant differences in the incidence rates among these countries. The aim of this study is to compare frequency of anal sphincter tears among the four Nordic countries, and to discuss the possible reasons for the development. STUDY DESIGN Ecological register study. Anal sphincter ruptures are registered as third and fourth degree perineal tears in the national birth and hospital registries in the Nordic countries. Data from these registries were sampled from Denmark, Finland, Norway and Sweden. The incidences of anal sphincter ruptures were calculated as percentages of all vaginal deliveries and caesarean sections were excluded. The test of relative proportions, Chi-square and linear regression modelling were used to study the difference between countries and time trends. RESULTS The frequency of anal sphincter rupture was significantly higher in three countries, Denmark 3.6%, Norway 4.1% and Sweden 4.2%, compared to Finland 0.6%. The trend was clearly increasing from the early 1970s in all countries. CONCLUSIONS There is a significant difference in the Nordic countries in the incidence of anal sphincter tears and a significant increment in the incidence over three decades. Our hypothesis is that change in the routines during labour may be one reason for this increment. Higher episiotomy frequency in Finland may be one contributing reason. We assume that there has been a change in the conduct of labour during the last decades, and protecting the perineum may have lost its importance in the three Nordic countries, while the classic method of protecting perineum is still in use in Finland.

Decreasing the Incidence of Anal Sphincter Tears During Delivery

OBJECTIVE: To estimate if an interventional program causes a decrease in the frequency of anal sphincter ruptures. METHODS: A total of 12,369 vaginal deliveries between 2002 and March 2007 were enrolled in the interventional cohort study. Slowing the delivery of the infant’s head and instructing the mother not to push while the head is delivered was the intervention. Data were analyzed in relation to occurrence of anal sphincter tears. RESULTS: The proportion of parturients with anal sphincter tears decreased significantly during the study period from 4.03% (285 of 7,069) to 1.17% (42 of 3,577) (P<.001). A similar decrease was observed for instrumental deliveries (from 16.26% to 4.90%; P<.001) and noninstrumental deliveries (from 2.70% to 0.72%; P<.001). Although the number of patients with fourth-degree anal sphincter ruptures from 2002 through 2004 was 10, 13, and 11 per year, respectively, there was just one fourth-degree anal sphincter rupture during the whole study period of 18 months (P<.001). The number of episiotomies increased from 13.9% (980 of 7,069) in the years 2002–2004, to 23.1% during the first 9 months of the intervention (416 of 1,776; P<.001), but decreased to 21.1% (381 of 1,801) during the last 9 months of the intervention. CONCLUSION: As a result of this intervention the number of anal sphincter ruptures was reduced from 4.03% to 1.17%. LEVEL OF EVIDENCE: II

Incidence of obstetric anal sphincter injuries after training to protect the perineum: cohort study.

Objective To compare the incidence of obstetric anal sphincter injuries (OASIS) in two time periods, before and after implementing a training programme for improved perineal support aimed at reducing the incidence of obstetric anal sphincter injuries. The secondary aim was to study incidence of obstetric anal sphincter injuries in subgroups defined by risk factors for OASIS. Design Population-based cohort study. Setting University hospital setting in Oslo, Norway. Participants Two cohorts of all delivering women in the largest hospital in Norway during two time periods (2003–2005 and 2008–2010) were studied. After excluding caesarean sections and preterm deliveries (< week 32), the study population consisted of 31 709 deliveries, among which 907 women were identified with obstetric anal sphincter injury. Primary and secondary outcome measures Incidence of OASIS in two time periods. Maternal, obstetrical and foetal risk factors for OASIS were collected from the hospital obstetric database. Univariate analyses and multivariate logistic regression analyses, presenting adjusted ODs for OASIS, were performed. Results The OASIS incidence was significantly reduced by 50%, from 4% (591/14787) in the first time period to 1.9% (316/16 922) in the second. This reduction could not be explained by changes in population characteristics or OASIS risk factors during the study years. The reduction of incidence of OASIS between the two study periods was consistent across subgroups of women; regardless of parity, delivery method and infant birth weight. Conclusions A marked reduction in the incidence of OASIS was observed in all studied subgroups of women after implementing the training programme for perineal protection. Further, this reduction could not be explained by the differences in patient characteristics across the study period. These findings indicate that the training programme with improved perineal protection markedly reduced the risk of OASIS.

Classification of episiotomy: towards a standardisation of terminology

Please cite this paper as: Kalis V, Laine K, de Leeuw J, Ismail K, Tincello D. Classification of episiotomy: towards a standardisation of terminology. BJOG 2012;119:522–526.

Prevalence and risk factors for anal incontinence after obstetric anal sphincter rupture

Objective. To study prevalence and risk factors for anal incontinence (AI) after obstetric anal sphincter rupture. Material and methods. This was a retrospective clinical observational study. Among 14 959 vaginal deliveries, 591 women were diagnosed with obstetric anal sphincter ruptures (3.9%) at one Norwegian University Hospital in 2003–2005. Patients were examined and interviewed approximately 10 months after delivery. Anal continence was classified with St. Marks incontinence score (0, complete anal continence; ≥3, anal incontinence), and defects in anal sphincter muscles were diagnosed by endoanal ultrasound. Prevalence of anal incontinence was assessed in relation to obstetrical and maternal characteristics as well as the correlation between anal incontinence and ultrasound‐detectable defects of sphincter muscle. Results. Anal incontinence with a St. Marks score of ≥3 was reported by 21% of women with obstetric anal sphincter rupture, with inability to control gas as the most prevalent symptom. Women with AI were more likely to report urinary incontinence compared with women having no AI. In a multiple regression analysis of maternal and obstetrical risk factors, fourth degree sphincter tear was the only significant risk factor for AI. Anal incontinence was more frequent in patients diagnosed with than without ultrasound‐identified anal sphincter muscle defects at 10 months postpartum follow‐up. Conclusion. Anal as well as urinary incontinence after delivery with obstetric anal sphincter rupture is common, and prenatal obstetric and maternal variables could not predict anal incontinence. Fourth degree perineal tear and a persistent ultrasound‐detected defect in the anal sphincter muscles are associated with AI.

Evaluation of the incision angle of mediolateral episiotomy at 60 degrees

To study the angle of mediolateral episiotomy at the time of cut, after primary repair, and 6 months postpartum; and the incidence and severity of perineal pain and anal incontinence 6 months after delivery.

Are obstetric anal sphincter ruptures preventable?– Large and consistent rupture rate variations between the Nordic countries and between delivery units in Norway

Objective. To study changes in the incidence of obstetric anal sphincter rupture (OASR) during recent years in Denmark, Finland, Sweden and Norway and hospital‐based incidence in recent years in Norway. Design. Retrospective birth register study. Setting. Unselected population of delivering women in four Nordic countries. Sample. All deliveries (574 175) registered in Denmark, Finland, Norway and Sweden, 2004–2010. Methods. Parity data, including maternal, obstetrical and fetal characteristics, were obtained. The incidence of OASR was calculated from vaginal deliveries. A chi‐squared test was used to analyse differences between countries and time periods. Main outcome measures. Incidence of OASR. Results. During the study period, the OASR incidence in Finland was notably lower (0.7–1.0%) than in the other three Nordic countries (4.2–2.3%). A significant and constant reduction in OASR incidence was observed in Norway only (from 4.1 to 2.3%, from 2004 to 2010, p < 0.001). This reduction occurred simultaneously with introduction of a national intervention program of improved delivery techniques that aimed to reduce the incidence of OASR. No major alterations in maternal or fetal risk factors for OASR or registration routines could explain this rapid reduction in the rate of OASR. Differences in the incidence of OASR between Norwegian delivery units were significant, with a threefold difference when comparing the units with lowest and highest incidences. Conclusions. Obstetric anal sphincter rupture seems to be preventable to a considerable extent, as indicated by the rapid and lasting reduction of OASR incidence after implementation of perineal protection programs in Norway. Improved delivery techniques should be implemented in all delivery units to prevent OASR as much as possible.

Changing associations of episiotomy and anal sphincter injury across risk strata: results of a population-based register study in Finland 2004-2011.

Objectives To evaluate the changing association between lateral episiotomy and obstetric anal sphincter injury (OASIS) for women with low and high baseline risk of OASIS. Design A population-based register study. Setting Data gathered from the Finnish Medical Birth Register for the years 2004−2011. Participants All women with spontaneous vaginal or vacuum-assisted singleton births in Finland (n=384 638). Main outcome measure OASIS incidence. Results During the study period, the incidence of OASIS increased from 1.3% to 1.7% in women with first vaginal births, including women admitted for first vaginal birth after a prior caesarean section and from 0.1% to 0.3% in women with at least one prior birth, whereas episiotomy rates declined from 56.7% to 45.5% and 10.1– 5.3%, respectively. At the study onset, when episiotomy was used more widely, it was negatively associated with OASIS in women with first vaginal births, but as episiotomy use declined it became positively associated with OASIS. Women with episiotomy were complicated by OASIS with clearly higher risk scores than women without episiotomy suggesting that episiotomy was clearly protective against OASIS. OASIS occurred with lower mean risk scores among women with and without episiotomy over time. However, OASIS incidences increased only among women with episiotomy, whereas it decreased or remained among women without episiotomy. Conclusions The cross-over effect between episiotomy and OASIS could be explained by increasing disparity in baseline OASIS risk between treated and untreated women, since episiotomy use declined most in women at low OASIS risk. Episiotomy rate can be safely reduced in low-risk women but interestingly along with the policy change the practice to cut the episiotomy became less protective among high-risk women.

Anal sphincter tears at spontaneous delivery: A comparison of five hospitals in Norway

Objective. To analyze circumstances relating to severe anal sphincter tears occurring at spontaneous delivery, in view of reported differences in practice regarding manual perineal protection during delivery. Design. Cohort study of midwife‐conducted non‐operative vaginal deliveries. Setting. Five Norwegian hospitals with 12,438 consecutive deliveries during a 12‐month period. Methods. Data from 357 women sustaining third and fourth grade anal sphincter tears (2.9%) were analyzed. Main outcome measures. Different incidence of major perineal tears. Results. Sphincter tear incidence varied significantly between the five hospitals, from 1.3 to 4.7% (p <0.001, RR=3.14 (CI: 2.38–5.56)). There was no significant difference between the five hospitals when other risk variables were compared. Use of oxytocin in the second phase of labor and of epidural analgesia was significantly more often applied in the hospital with the lowest rate of sphincter tears. The midwives’ perception of having applied perineal support was not significantly different between the two hospitals with the highest and the lowest incidence of sphincter tear. Conclusion. The observed difference in incidence of sphincter tear between the hospitals remains unexplained, but could be due to different perineal protection handling techniques.

The association of episiotomy with obstetric anal sphincter injury--a population based matched cohort study.

Objectives To estimate the independent association of episiotomy with obstetric anal sphincter injuries (OASIS) using first a cross-sectional and then a matched pair analysis. Design A matched cohort. Setting Data was gathered from the Finnish Medical Birth Register from 2004–2011. Population All singleton vaginal births (n = 303,758). Methods Women resulting matched pairs (n = 63,925) were matched based on baseline risk of OASIS defined based on parity (first or second/subsequent vaginal births), age, birth weight, mode of delivery, prior caesarean section, and length of active second stage of birth. Results In cross-sectional analysis episiotomy was associated with a 12% lower incidence of OASIS (adjusted odds ratio (aOR) 0.88, 95% confidence interval (CI) 0.80 to 0.98) in first vaginal births and with a 132% increased incidence of OASIS in second or subsequent vaginal births (aOR 2.32, 95% CI 1.77 to 3.03). In matched pair analysis episiotomy was associated with a 23% (aOR 0.77, 95% CI 0.69 to 0.86) lower incidence of OASIS in first vaginal births and a 61% (aOR 1.61, 95% CI 1.14 to 2.29) increased incidence of OASIS in second or subsequent vaginal births compared to women who gave birth without an episiotomy. The matched pair analysis showed a 12.5% and a 31.6% reduction in aORs of OASIS associated with episiotomy, respectively. Conclusions A matched pair analysis showed a substantial reduction in the aORs of OASIS with episiotomy, due to confounding by indication. This indicates that results of observational studies evaluating an association between episiotomy and OASIS should be interpreted with caution.