Temporal trends in the incidence of and associations between the risk factors for obstetrical anal sphincter injuries

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.

Effect of the "shoulder-up" bundle on the incidence of spontaneous perineal injury after vaginal delivery: comparison of 2 historic cohorts after propensity score matching

BACKGROUND

Perineal injury following vaginal delivery represents a major cause of long-term maternal morbidity, and its prevention is among the priorities of modern obstetrical practice.

OBJECTIVE

This study aimed to investigate whether the systematic implementation of a bundle of maneuvers to prevent perineal injury (ie, the "shoulder-up" bundle) may reduce the rate of spontaneous perineal tears in women delivering at a single tertiary maternity unit.

STUDY DESIGN

This was a single-center retrospective intervention study including all vaginal deliveries between April 1, 2020 and March 31, 2022. On March 1, 2021, a bundle focused on perineal injury prevention in vaginal deliveries was implemented and introduced as a standard of care. The "shoulder-up" bundle includes the addition of a hands-on technique for the delivery of the posterior shoulder, which is slowly lifted up under the direct visualization of the perineal body, immediately after the disengagement of the anterior shoulder. The labor ward staff underwent dedicated training to acquire expertise on the "shoulder-up" bundle. Little changes in terms of medical and midwifery staffing were recorded during the study period. The incidence of spontaneous second-degree or higher perineal tears was compared between the patients who gave birth before the clinical implementation of the bundle (standard-care group) and those who were delivered following the implementation of the bundle (shoulder-up group). A 1:1 propensity score matching of the 2 groups was done for the variables that proved to be independently associated with the perineal outcome.

RESULTS

From April 1, 2020 to March 31, 2022, 3671 patients had a vaginal birth at our tertiary care unit (1786 in the standard-care group and 1885 in the "shoulder-up" group) and were enrolled in the study population. Of these, 1191 (32.4%) had a spontaneous second-degree or higher perineal tear. At univariate analysis, nulliparity (59.6% vs 39.1%; P<.001), higher gestational age at delivery (39.8±1.28 vs 39.4±1.97 weeks; P<.001), epidural analgesia (40.6% vs 31.2%; P<.001), vacuum-assisted delivery (9.6% vs 4.0%; P<.001), and birthweight >4 kg (11.0% vs 6.3%; P<.001) were independently associated with the perineal outcome. Following propensity score matching for the above cited factors, the 1703 patients of each group were compared. A significant increase in the rate of intact perineum (71.0% vs 64.1%; P=.014) and a reduction in the incidence of second- (27.2% vs 32.9%; P=.006) and third to fourth-degree perineal tears (1.3% vs 3.0%; P<.001) was demonstrated in the "shoulder-up" group. Among the subgroup of patients undergoing vacuum-assisted delivery, a borderline significant reduction in the rate of obstetrical anal sphincter injury (10.4% vs 2.9%; P=.052) was also observed.

CONCLUSION

Our study showed that the clinical implementation of the "shoulder-up" bundle at vaginal delivery is associated with a significant reduction in the incidence of spontaneous second-degree or higher perineal tears.

Substantial Obstetric Anal Sphincter Injury during Vacuum Assisted Delivery: An Obstetrical Issue or Device Related?

BACKGROUND

Obstetric anal sphincter injuries (OASIS) might be associated with long-term urinary and anorectal morbidities. The aim of the study was to investigate the risk factors and clinical implications of OASIS associated with vacuum-assisted deliveries versus normal vaginal deliveries.

METHODS

A series of 413 consecutive OASIS cases were retrospectively analyzed. A comparison was made between OASIS cases diagnosed following vacuum-assisted deliveries versus OASIS cases diagnosed following normal vaginal deliveries. Multivariable analysis was used to study the association between vacuum-assisted deliveries and superficial (3A and 3B) versus deep (3C and 4) perineal tears.

RESULTS

The study population comprised 88,123 singleton vaginal deliveries. Diagnosis of OASIS was made in 413 women (0.47% of the total cohort), 379 (91.8%) of whom had third-degree tears and 34 (8.2%) of whom had fourth-degree tears. Among the 7410 vacuum-assisted deliveries, 102 (1.37%) had OASIS, whereas, among the 80,713 normal vaginal deliveries, only 311 (0.39%) had OASIS. In a multivariate analysis, only vacuum-assisted delivery was found to be associated with a significant risk of deeper (3C or 4) perineal tears (OR = 1.72; 95% CI 1.02-2.91; p = 0.043).

CONCLUSIONS

Vacuum-assisted instrumental intervention is a significant risk factor for OASIS and especially for deeper tears, independent of other maternal and obstetric risk factors.

Postpartum ultrasound for the diagnosis of obstetrical anal sphincter injury

This review presents the available data on the diagnosis of obstetrical anal sphincter injury by postnatal ultrasound imaging. There is increasing evidence that anal sphincter tears are often missed after childbirth and, even when diagnosed, often suboptimally repaired, with a high rate of residual defects after reconstruction. Even after postpartum diagnosis and primary repair, 25% to 50% of patients will have persistent anal incontinence. As clinical diagnosis may fail in the detection and classification of obstetrical anal sphincter injury, the use of imaging has been proposed to improve the detection and treatment of these lacerations. Notably, 3-dimensional endoanal ultrasound is considered the gold standard in the detection of obstetrical anal sphincter injury, and recently, 4-dimensional transperineal ultrasound, commonly available in obstetrical and gynecologic settings, has proven to be effective as well. Avoidance of forceps delivery when possible, performance of a rectal examination after vaginal delivery and before repair of any severe perineal tear, and offering sonographic follow-up at 10 to 12 weeks after vaginal delivery in high-risk women (maternal age of ≥35 years, vaginal birth after cesarean delivery, forceps, prolonged second stage of labor, overt obstetrical anal sphincter injury, shoulder dystocia, and macrosomia) may help reduce morbidity arising from anal sphincter tears.

Obstetric anal sphincter injury following previous vaginal delivery

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injury (OASI) is a debilitating complication of vaginal delivery. The aim of this study was to identify risk factors for OASI in women with a previous vaginal delivery. We further attempted to detect specific risk factors for severe OASI in this subgroup.

METHODS

We conducted a retrospective cohort study between 2003 and 2019. The study group included women who had a singleton, live, vertex, vaginal delivery at term and who also had at least one previous vaginal delivery. The control group included women with at least one previous vaginal delivery without OASI. General medical history, obstetric history, and ante-, intra- and post-partum data were collected and compared between groups.

RESULTS

Following implementation of the inclusion criteria, 79,176 women were included. Allocation to study groups was according to OASI occurrence: 135 patients (0.2%) had a third- or fourth-degree perineal tear, while 79,041 patients (99.8%) had no such injury. Multivariate analysis revealed that one previous vaginal delivery, birthweight ≥ 3900 g (90th percentile), vacuum-assisted vaginal delivery and episiotomy were associated with increased risk of OASI. Comparison of more severe OASI (3C and 4th-degree) cases to the control group showed similar results with the addition of prolonged second stage and younger age to risk factors associated with severe OASI while episiotomy was no longer significant.

CONCLUSION

In women with a previous vaginal delivery, one vs. two or more previous vaginal deliveries, increased birthweight, vacuum-assisted vaginal delivery and episiotomy are risk factors for OASI.

Fourth degree perineal tears: Surgical repair technique in 10 steps

Obstetrical anal sphincter injury (OASIS) may lead to significant comorbidities, including anal incontinence, rectovaginal fistula, and pain. A correct repair is required to avoid improper healing, as a persistent defect in the external anal sphincter after delivery can increase the risk of complications and worsening of symptoms following subsequent vaginal deliveries. Herein is described the surgical repair technique for a fourth degree perineal tear. Regarding resident education, there are challenges associated with the proper training in OASIS repair. The procedure is illustrated by an instructive video article that standardizes the essential steps to make the technique ergonomic and easy to perform with step-by-step explanations.