Risk of anal sphincter injury in trial of labor post cesarean section

How to Avoid Becoming a Risk Factor of Fecal Incontinence Due to OASIS-A Narrative Review

Third- and fourth-degree anal sphincter injuries are among the most severe traumas women can experience during childbirth, often leading to lifelong continence issues. Despite extensive research, current repair techniques are often inadequate, failing to provide long-term efficiency. The repair of OASIS tends to worsen with time as fecal or anal incontinence increases. This article presents the risk factors for primary repair failure differently from those previously described in the literature, specifically focusing on avoidable risk factors related to obstetricians and surgeons who perform OASIS repair. After reviewing the literature, the following risk areas were identified and described: recurrent OASIS, pitfalls of the current WHO classification, surgical techniques, place in which the repair should be performed, surgical training, factors related to low volumes of patients with grade III-IV injuries, timing of the repair, and failure of primary repair.

Is vaginal birth after cesarean section a risk factor for obstetric anal sphincter injury?

OBJECTIVE

To investigate whether women undergoing their first vaginal delivery after a previous cesarean section (secundiparous) are at increased risk for obstetric anal sphincter injury (OASI) compared with primiparous women.

METHODS

A retrospective cohort study of 85 428 women who delivered vaginally over a 10-year period in a single tertiary medical center. Incidence of OASI, risk factors, and clinical characteristics were compared between primiparous women who delivered vaginally and secundiparous women who underwent their first vaginal birth after cesarean section (VBAC). A multivariable logistic regression analysis was used to study the association between VBAC and OASI.

RESULTS

Overall, 36 250 primiparous and 1602 secundiparous women were enrolled, 309 of whom had OASI. The rates of OASI were similar among secundiparous women who had VBAC and primiparous women who underwent vaginal delivery (15 [0.94%] vs 294 [0.81%], P = 0.58). The proportions of third- and fourth-degree tears were also similar among secundiparous and primiparous women who experienced OASI (87% vs 91.5%, and 13% vs 8.5%, respectively, P = 0.68). Furthermore, the rates of OASI were similar in both study groups, although secundiparous women who underwent VBAC had higher rates of birth weights exceeding 3500 g (414 [25.8%] vs 8284 [22.8%], P = 0.016), and higher rates of vacuum-assisted deliveries (338 [21%] vs 6224 [17.2%], P < 0.001). A multivariate logistic regression analysis failed to establish a statistically significant association between VBAC and OASI (odds ratio 0.672, 95% confidence interval 0.281-1.61, P = 0.37).

CONCLUSIONS

No increased risk for OASI was found in secundiparous women who underwent VBAC compared with primiparous women at their first vaginal birth.

Risk indicators for obstetrical anal sphincter injury in vaginal birth after caesarean section compared to first vaginal delivery

OBJECTIVES

Comparison of the rate of obstetric anal sphincter injury (OASI) between women having their first vaginal birth after caesarean section (CS) and true nulliparous women with a vaginal delivery. Assessment of risk indicators for OASI in women with vaginal birth after one CS (VBAC).

STUDY DESIGN

28 535 women with their first VBAC and a cohort of 275 439 nulliparous women with a vaginal delivery of a liveborn infant in a cephalic position from the Dutch perinatal registry were analyzed. We compared the OASI rate with univariate and multivariate analysis. In women with VBAC possible risk indicators for OASI were assessed using univariate and multivariate logistic regression analysis.

RESULTS

The rate of OASI was 5.2% in women with vaginal birth after CS and 4.0% in women with a first vaginal delivery. The adjusted OR (aOR) for vaginal birth after an elective CS was higher (aOR 1.34, 95% CI 1.23-1.47) compared to vaginal birth after an emergency CS (aOR 1.16, 95% CI 1.08-1.25). In women with vaginal birth after emergency CS, the aOR for the indication non-progressive labor was 1.18 (95% CI 1.08-1.29), whereas CS for suspected fetal distress was not significantly associated with obstetric anal sphincter injury in VBAC. In the 28 535 women with a VBAC, mediolateral episiotomy (MLE), birth weight < 3000 g and maternal age < 25 years were associated with a significantly lower rate of OASI. A gestational age of 42 weeks, birth weight ≥ 3500 g, operative vaginal delivery and duration of the 2nd stage of labour of ≥ 60 min were associated with a significantly higher rate of OASI.

CONCLUSIONS

Women with a VBAC have a higher rate of OASI in comparison with women with a first vaginal delivery, with the exception of women with a vaginal birth after an emergency CS for suspected fetal distress. Factors associated with a significantly lower rate for OASI were MLE, maternal age < 25 and birth weight < 3000 g. A gestational age of 42 weeks, birth weight between 3500 and 4000 g and ≥ 4000 g, operative vaginal delivery and duration of the 2nd stage of delivery longer dan 60 min were associated with a significantly higher rate of OASI.

Three-Dimensional Ultrasound Imaging under Optimized Nuclear Regression Reconstruction Algorithm in the Diagnosis Vaginal Delivery and Cesarean Section on the Anal Sphincter Complex of Primiparas

This study was aimed at analyzing the injury of anal sphincter (AS) for primipara caused by the vaginal delivery and cesarean section under the guidance of three-dimensional (3D) ultrasound images. A total of 160 patients who underwent postpartum reexamination were enrolled as the research subjects, including 80 cases of natural delivery (group A) and 80 cases of cesarean section pregnant women (group B), all of whom underwent three-dimensional ultrasound imaging scans. At the same time, an optimized kernel regression reconstruction (KRR) algorithm was proposed for the enhancement of ultrasound images. It was found that the running time after acceleration by the graphics processing unit (GPU) was obviously superior to that of a single-threaded CPU and a multithreaded CPU, showing statistical differences (P < 0.05). The thickness of the proximal and distal external AS in group A was much thinner in contrast to that in group B, showing statistical difference (P < 0.05). Therefore, the 3D ultrasound image based on the optimized KRR algorithm can accurately assess the morphology of AS injury in primipara, and the adverse effect of natural delivery on the AS complex in primipara was greater than that of cesarean section.

Increased risk of obstetric anal sphincter injury in women undergoing vaginal delivery after caesarean section: A systematic review and meta-analysis

BACKGROUND

There is increased focus on obstetric anal sphincter injury (OASI) and there are several well-established risk factors such as birthweight, instrumental delivery and median episiotomy. Some studies have found increased risk of OASI in women delivering vaginally after a previous caesarean section (VBAC).

OBJECTIVE

To evaluate whether there is increased prevalence of OASI in VBAC compared with primiparous women.

SEARCH STRATEGY

Literature search using PubMed, Embase and Cochrane databases.

SELECTION CRITERIA

All studies with data on both primiparous women and women undergoing VBAC were included. All included studies were evaluated using the "SIGN - methodology checklist" to verify if the quality was acceptable.

DATA COLLECTION AND ANALYSIS

This systematic review included 23 articles conducted in 11 countries over 19 years. Included studies were analysed using RevMan version 5.4.

MAIN RESULTS

We found increased prevalence of OASI in the VBAC group; 8.18% (95% confidence interval [CI] 8.07-8.29) compared with 6.59% (95% CI 6.56-6.62) in primiparous women. Correspondingly, the meta-analysis revealed increased prevalence for OASI in the VBAC group (odds ratio 1.27, 95% CI 1.10-1.47). We found a high level of heterogeneity (I²  = 98%).

CONCLUSION

Women undergoing VBAC had a higher prevalence of OASI compared with primiparous women.

Risk factors for obstetric anal sphincter injury among women undergoing a trial of labor after cesarean

OBJECTIVE

Data regarding the risks of obstetrical anal sphincter injury (OASI) among women who never delivered vaginally undergoing a trial of labor after cesarean (TOLAC) are scarce. We aimed to evaluate the risk factors and the rate of OASI among women undergoing TOLAC who never delivered vaginally.

STUDY DESIGN

A retrospective cohort study of all women undergoing a TOLAC and never delivered vaginally between 3/2011 and 6/2020. Maternal and intrapartum characteristics were compared between OASI and no-OASI groups. We matched groups to earliest gestational age in which OASI has occurred. A further comparison was made between the study cohort and a cohort of primiparous women undergoing a vaginal delivery, including gestational ages at which OASI has occurred in that cohort.

RESULTS

During the study period there were 2061 TOLACs among women without prior vaginal delivery. Of these, 76 % (1566/2061) had a successful vaginal delivery. Overall, 22/2061 (1.1 %) cases of OASI occurred. There was no difference in maternal demographic, obstetrical and medical history characteristics between the study groups. The mean gestational age at TOLAC was lower in the OASI group (39^0/7 ± 1^2/7 vs. 39^5/7 ± 1^2/7, p = 0.012). In multivariable regression analysis, gestational age was negatively associated with OASI [adjusted odds ratio, 95 % (confidence interval) 0.95 (0.91-0.99), for each day increase in gestational age)]. The rate of OASI in the study cohort did not differ from the rate of OASI among primiparous women during the same study period (347/27975, 1.2 %, p = 0.686).

CONCLUSION

Gestational age at delivery is the only predictor of OASI among women with no prior vaginal deliveries undergoing a TOLAC. The incidence of OASI in this population is 1.1 % and does not differ from that of primiparous women.