Risk factors for rupture of the anal sphincter

Relationship between Perineal Body Length and Degree of Perineal Tears in Primigravidas Undergoing Vaginal Delivery with Episiotomy

Background

Perineal tears are one of the most common complications of vaginal delivery. Severe perineal tears can cause various morbidities. There are many factors that affect the occurrence of perineal tears. One of the major factors related to the occurrence of perineal tears is the length of the perineal body. However, until now, no research in Indonesia has concluded that the length of perineal body can predict the perineal tears.

Objective

To find the relationship between perineal body length and perineal tears, so it can provide a reference on the use of perineal body length to predict severe perineal tears in vaginal delivery with episiotomy.

Methods

This nested case-control study was conducted at RSUD Tangerang and RSUD Karawang in Indonesia from February to September 2017. A total of 126 primigravida patients participated in the study consecutively. The length of the perineal body was then measured and followed until the start of the second stage of labor. Afterwards, the perineal length and degree of perineal tears were assessed using unpaired T-test for bivariate analysis, multivariate analysis, and scoring test to predict the occurrence of third- and fourth-degree of perineal tears with power calculation (β) 80% and Zβ 0.842.

Results

There was a significant difference in mean length of the perineal body between the group with first- and second-degree perineal tears and the group with third- and fourth-degree perineal tears (p < 0.001). From the multivariate analysis, adjusted OR was 5.26 (95% CI 1.52-18.17). Score test was performed to predict the occurrence of third- and fourth-grade perineal tears. Perineal body length and head circumference could be used as predicting factors of perineal tears. Perineum length ≤ 3.0 cm and head circumference ≥ 33.5 cm posed a risk of perineal tears of third and fourth degrees (70.52%).

Conclusion

The length of the perineal body has a good ability to predict the occurrence of perineal tears.

Modifiable risk factors of obstetric anal sphincter injury in primiparous women: a population-based cohort study

OBJECTIVE

To determine modifiable risk factors and incidence of obstetric anal sphincter injury (OASIS) in primiparous women.

STUDY DESIGN

We performed a population-based retrospective cohort study, using data from the Danish Medical Birth Registry. The population consisted of primiparous women with a vaginal delivery in the time period 2000-2010. Univariable and multivariable logistic regressions were used to determine risk factors of OASIS. Main outcome measures were incidence of OASIS in first vaginal delivery, odds ratios for possible risk factors: age, body mass index, birthweight, head circumference, gestational age, presentation, induction of labor, oxytocin augmentation, epidural, mediolateral episiotomy, vacuum extraction, forceps, shoulder dystocia, and year of delivery.

RESULTS

Of 214,256 primiparous women with a vaginal delivery, 13,907 (6.5%; 95% confidence interval [CI] 6.4-6.6%) experienced an OASIS. The incidence of OASIS increased in the time period (adjusted odds ratio [aOR], 1.02; 95% CI, 1.02-1.03; P < .0001, per year). We found a protective effect of epidural analgesia (aOR, 0.84; 95% CI, 0.81-0.88; P = .0001). Vacuum extraction without episiotomy was a significant risk factor of OASIS (aOR, 2.99; 95% CI, 2.86-3.12; P < .0001), and episiotomy was protective in vacuum-assisted deliveries compared with vacuum-assisted deliveries without episiotomy (aOR, 0.60; 95% CI, 0.56-0.65; P < .0001). Birthweight was found to be an important nonmodifiable risk factor (aOR, 2.76; 95% CI, 2.62-2.90; P < .0001).

CONCLUSION

Epidural analgesia in itself was protective against OASIS. Vacuum extraction increased the risk of OASIS, although mediolateral episiotomy was protective when applied in deliveries assisted by vacuum extraction.

Immediate or delayed repair of obstetric anal sphincter tears-a randomised controlled trial

OBJECTIVE

To investigate if an 8- to 12-hour time delay of primary repair affects anal incontinence at 1-year follow up.

DESIGN

Randomised controlled trial.

SETTING

University hospital in Sweden.

POPULATION

A total of 165 women diagnosed with a third- to fourth-degree perineal tear.

METHODS

The participants were randomised to immediate or delayed (8- to 12-hour delay) end-to-end repair; 78 were allocated to immediate operation and 87 to a delayed repair. An incontinence and pelvic floor symptom questionnaire was completed by the participants at baseline and at 6- and 12-month follow up.

MAIN OUTCOME MEASURES

Anal incontinence measured by the validated Pescatori incontinence score.

RESULTS

A total of 161 (98%) and 155 (94%) women completed the two follow-up questionnaires. There was no significant difference in anal incontinence between the groups. There were no significant differences in pelvic floor symptoms between the groups. A multivariate proportional odds model revealed that increasing maternal age was significantly associated with both increased symptoms of faecal urgency and inability to discriminate flatus from faeces.

CONCLUSION

Delayed repair provided the same functional outcome at 1-year follow up. Delaying the repair should thus not be recommended routinely, but can be an alternative under special circumstances when appropriate surgical expertise is not readily available.

Risk scoring system for prediction of obstetric anal sphincter injury

OBJECTIVE

The objective was to begin the process of developing an antenatal risk scoring system, as a first step towards examining whether elective Caesarean section for women at high risk of injury could be an effective and acceptable intervention.

DESIGN

Retrospective study.

SETTING

Tertiary maternity unit in the UK.

POPULATION

One hundred and twenty-three women who sustained an obstetric anal sphincter injury (OASI) and 123 controls without OASI.

METHODS

Case notes of women with a third or fourth degree tear between 1997 and 1999 were examined for risk factors. Controls matched for age and week of delivery were identified from the maternity record database and case records reviewed for the presence of risk factors. Unweighted and weighted risk scores were produced using odds ratios, and compared between cases and controls. Receiver operating characteristics (ROC) curve analysis of the risk scores was performed to discriminate between cases and controls and to calculate the sensitivity and specificity of each scoring system.

MAIN OUTCOME MEASURES

Odds ratio (OR) and 95% confidence interval (CI) for each risk factor. Sensitivity and specificity from ROC curves for weighted and unweighted risk score.

RESULTS

Among the cases there were more nulliparous women (OR 1.77; CI 1.05-2.99) and a trend towards more women with an episiotomy (OR 1.57; CI 0.99-2.47). Among women with sphincter injury, trends towards more epidurals (OR 1.64; CI 0.97-2.75), and more babies weighing more than 4000 g among (OR 1.45; CI 0.85-2.49) were noted. The median unweighted risk score was 2 for cases and 2 for controls (P= 0.05), while the weighted risk score was 2.1 and 1.37 (P= 0.03), respectively. The ROC curves approximated to a straight line demonstrating very poor discrimination between cases and controls.

CONCLUSION

The predictive test performed poorly, suggesting that the risk factors identified do not exert a large enough effect in a cohort of this size.

Rupture of the sphincter ani: the recurrence rate in second delivery

BACKGROUND

Injury to the genital tract sustained during childbirth can lead to transient or protracted morbidity. Attention should be paid to avoidable risk factors that can cause this complication.

AIM

To analyse the recurrence, at a later delivery, of trauma to the genital tract, subsequent to perineal laceration of the sphincter ani (third or fourth degree), sustained at an earlier delivery.

DESIGN

A population-based study.

SETTING

In Sweden, 1973-1997 inclusive.

POPULATION

All women with a vaginal, singleton delivery in Sweden.

METHODS

The Medical Birth Registry, the National Board of Health and Welfare, was used to identify cases of ruptured sphincter ani.

MAIN OUTCOME MEASURES

OR was calculated with 95% confidence interval. A stratified analysis was performed using the Mantel-Haenszel technique. Major end point Rupture of the sphincter ani (third or fourth degree) at second delivery.

RESULTS

The incidence of anal sphincter rupture increased sixfold during the study period, from 0.5% in 1973 to 3.0% in 1997. Women who had sustained a laceration of this type ran a significantly increased risk of a recurrence at a later delivery. This effect persisted even after stratification for birthweight, year of birth, parity and maternal age (OR 4.74, 95% confidence interval 4.34-5.17). When only fourth degree rupture was considered (rupture of both anal sphincter and rectum), the corresponding figures were 6.52 (95% CI 5.29-8.04). This effect also persisted after stratification for birthweight, year of birth, parity and maternal age. The OR for giving birth a second time, subsequent to a third or fourth degree perineal laceration at first delivery, was 0.68 (95% CI 0.67-0.70).

CONCLUSION

Our findings suggest that the risk of an anal sphincter rupture at delivery increases five to sevenfold when there has been a similar rupture at a previous delivery. Further study is needed before safe recommendations can be made concerning the subsequent mode of delivery to be adopted, following rupture in the sphincter ani at a previous birth.

Vaginal birth and perineal trauma

Vaginal birth has been recognized as being potentially traumatic to the pelvic floor. It is important that contributory obstetric factors are identified and their occurrence minimized. Women who have sustained significant anal sphincter injury are at greater risk of further damage and faecal incontinence with subsequent deliveries. This review reports on recent developments in this field, and examines ways in which morbidity might be reduced.