Risk factors for obstetric anal sphincter injury: To prolong or to vacuum?

Neonatal head circumference as a risk factor for obstetric anal sphincter injuries: a systematic review and meta-analysis

OBJECTIVE

Between 53% and 79% of women will sustain some degree of perineal laceration during vaginal delivery. Third- and fourth-degree perineal lacerations are known as obstetric anal sphincter injuries. Timely diagnosis and prompt treatment of obstetric anal sphincter injuries can help to prevent the development of severe consequences like fecal incontinence, urinary incontinence, and rectovaginal fistula. Neonatal head circumference is routinely measured postpartum but is often not mentioned as a risk factor for obstetric anal sphincter injuries in clinical guidelines. Thus far, no review article on the risk factors for obstetric anal sphincter injuries has discussed the role of neonatal head circumference. This study aimed to review and analyze the relationship between head circumference and the occurrence of obstetric anal sphincter injuries among previous studies to conclude whether head circumference should be recognized as an important risk factor.

DATA SOURCES

Through study screening on Google Scholar, PubMed, Scopus, and Science Direct for articles published between 2013 to 2023, followed by assessment of eligibility, this study ended up reviewing 25 studies, 17 of which were included in the meta-analysis.

STUDY ELIGIBILITY CRITERIA

Only studies that reported both the neonatal head circumference and the occurrence of obstetric anal sphincter injuries were included in this review.

METHODS

The included studies were appraised using the Dartmouth Library risk of bias assessment checklist. Qualitative synthesis was based on the study population, findings, adjusted confounding factors, and suggested causative links in each study. Quantitative synthesis was conducted using calculation and pooling of odds ratios and inverse variance using Review Manager 5.4.1.

RESULTS

A statistically significant association between head circumference and obstetric anal sphincter injuries was reported in 21 of 25 studies; 4 studies reported that head circumference was a true independent risk factor. A meta-analysis of the studies that reported neonatal head circumference as a dichotomous categorical variable with a cutoff point of 35±1 cm yielded statistically significant pooled results (odds ratio, 1.92; 95% confidence interval, 1.80-2.04).

CONCLUSION

The risk for obstetric anal sphincter injuries increased as the neonatal head circumference increased-this should be considered in decision-making during labor and postpartum management to attain the best outcome.

Anal incontinence after a prolonged second stage of labor in primiparous women

The objective was to investigate the effect of delivery mode on anal incontinence 1–2 years after delivery in primiparous women with prolonged second stage of labor. This population-based cohort and questionnaire study performed in Stockholm Region, Sweden, included 1302 primiparous women with a second stage ≥ 3 h from December 1st, 2017 through November 30th, 2018. Background characteristics and outcome data were retrieved from computerized records. Questionnaires based on Wexner score were distributed 1–2 years after delivery. Risk of anal incontinence, defined as Wexner score ≥ 2, was calculated using logistic regression and presented as crude and adjusted odds ratios (OR and aOR) with 95% confidence intervals (CI). Compared with cesarean section, vacuum extraction was associated with anal incontinence (aOR 2.25, 95% CI 1.21–4.18) while spontaneous delivery was not (aOR 1.55, 95% CI 0.85–2.84). Anal incontinence was independently associated with obstetric anal sphincter injuries (aOR 2.03, 95% CI 1.17–3.5) and 2nd degree perineal tears (aOR 1.36, 95% CI 1.03–1.81) compared with no or 1st degree perineal tear. Obstetric anal sphincter injury at vacuum extraction inferred the highest risk of anal incontinence (aOR 4.06, 95% CI 1.80–9.14), compared with cesarean section. Increasing duration of the prolonged second stage did not affect the risk.

Risk of obstetric anal sphincter injury among women who birth vaginally after a prior caesarean section: A state-wide cohort study

OBJECTIVE

Vaginal birth after caesarean (VBAC) has been suggested to be associated with an increased risk of obstetric anal sphincter injury (compared with primiparous women who birth vaginally). However, prior studies have been small, or used outdated methodology. We set out to validate whether the risk of obstetric anal sphincter injury among women having their first VBAC is greater than that among primiparous women having a vaginal birth.

DESIGN

State-wide retrospective cohort study.

SETTING

Victoria, Australia.

POPULATION

All births (455,000) between 2009-2014.

METHODS

The risk of severe perineal injury between first vaginal birth and first vaginal birth after previous caesarean section was compared, after adjustment for potential confounding variables. Covariates were examined using logistic regression for categorical data and Wilcoxon rank-sum test for continuous data. Missing data were handled using multiple imputation; the analysis was performed using regression adjustment and Stata v16 multiple imputation and teffects suites.

RESULTS

Women having a VBAC (n=5,429) were significantly more likely than primiparous women (n=123,353) to sustain a 3^rd or 4^th degree tear during vaginal birth (7.1 vs 5.7%, p<0.001). After adjustment for mode of birth, body mass index, maternal age, infant birthweight, episiotomy and epidural, there was a 21% increased risk of severe perineal injury (relative risk 1.21 (95%CI 1.07 - 1.38)).

CONCLUSIONS

Women having their first vaginal birth after caesarean section have a significant increased risk of sustaining a 3^rd or 4^th degree tear, compared with primiparous women having a vaginal birth. Patient counselling and professional guidelines should reflect this increased risk.

The impact of a nationwide hands-on workshop on the diagnostic rates and management of obstetrical anal sphincter Injuries in Israel

AIM

The aim was to evaluate the influence of a half day, hands-on, workshop on the detection and repair of obstetric anal sphincter injuries (OASIs).

METHOD

Starting in February 2011, hands-on workshops for the diagnosis and repair of OASIs were delivered by trained urogynaecologists in departments of tertiary medical centres in Israel. The structure of the hands-on workshop resembles the workshop organized at the International Urogynecological Association annual conferences. Participants included medical staff, midwives and surgical residents from each medical centre. We collected data regarding the rate of OASIs, 1 year before and 1 year following the workshop, in 11 medical centres. The study population was composed of parturients with the following inclusion criteria: singleton pregnancy, vertex presentation and vaginal delivery. Pre-viable preterm gestations (< 24 weeks), birth weight < 500 g, stillborn, and those with major congenital anomalies, multifoetal pregnancies, breech presentations and caesarean deliveries were excluded from the analysis.

RESULTS

In the reviewed centres, 70 663 (49.3%) women delivered prior to the workshop (pre-workshop group) and 72 616 (50.7%) women delivered following the workshop (post-workshop group). Third- or fourth-degree perineal tears occurred in 248 women (0.35%) before the workshop, and in 328 (0.45%) following the workshop, a significant increase of 28.7% (P = 0.002). The increase in diagnosis was significant also in women with third-degree tears alone, 226 women (0.32%) before the workshop and 298 (0.41%) following the workshop, an increase of 28.3% (P = 0.005).

CONCLUSION

The detection rate of OASIs has significantly increased following the hands-on workshop. The implementation of such programmes is crucial for increasing awareness and detection rates of OASI following vaginal deliveries.

Maternal and neonatal outcomes following a prolonged second stage of labor: A meta-analysis of observational studies

Several articles investigated the impact of prolonged second stage of labor on maternal and neonatal outcomes; however, strict consensus is still lacking. The purpose of the present meta-analysis is to investigate risk factors that contribute to the pathophysiology of prolonged labor as well as effect sizes of maternal and neonatal morbidity. We searched Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL and Google Scholar database. Observational studies (prospective and retrospective) were considered eligible for inclusion in the present meta-analysis. To minimize the possibility of article losses we avoided language, country and date restrictions. Meta-analysis was performed with the RevMan 5.3 and secondary analysis with Rstudio. Overall, 13 studies were included in the present systematic review that comprised 337.845 parturient. Prolonged second stage was associated with higher odds of postpartum hemorrhage, chorioamnionitis, endometritis, postpartum fever and obstetric anal sphincter injury. Persistent occiput posterior position and shoulder dystocia were also more prevalent compared to women with normal duration of the second stage. The need for admission to the neonatal intensive care unit was higher as well as the risk of developing neonatal sepsis. On the other hand, the odds of perinatal death were comparable among cases with prolonged and normal duration of the second stage. The results of the present meta-analysis clearly indicate that deliveries following a prolonged second stage of labor are at increased risk of maternal and neonatal complications. The presented effect estimates can be used in current clinical practice during patient counseling.

Risk factors for obstetric anal sphincter injuries at vaginal birth after caesarean: a retrospective cohort study

INTRODUCTION AND HYPOTHESIS

Vaginal birth after caesarean (VBAC) is associated with an increased risk of obstetric anal sphincter injuries (OASIS). However, specific factors that influence the risk of OASIS at VBAC have not been studied, particularly whether there are specific baseline characteristics of the first delivery which affect the subsequent perineal outcomes.

METHODS

Retrospective analysis of prospectively collected data from University of Southampton NHS Foundation Trusts' maternity database. This included secundiparous women with a previous caesarean delivery (CS) who achieved a singleton, term, cephalic vaginal delivery from 2004 to 2014. Univariate analysis compared maternal, intrapartum and neonatal factors of those who suffered OASIS at VBAC with those who did not. A binary logistic regression model calculated the adjusted, independent odds ratio (OR) of OASIS.

RESULTS

A total of 1375 women met the inclusion criteria. The OASIS rate was 8.1%, a 1.4-fold increase compared with primiparous women [difference 2.4% (95% CI 1.1, 3.6)]. Those sustaining OASIS at VBAC were older (p = 0.011) and had infants of greater birth weight at initial caesarean (p < 0.001) and VBAC (p = 0.04). Analysis of odds ratios revealed that mediolateral episiotomy (MLE) at VBAC halved the risk of OASIS [37.5% VBAC with OASIS vs. 52.2% VBAC without OASIS (OR 0.51, 95% CI 0.32-0.81)], whereas an urgent CS at initial delivery doubled the risk [52.3% VBAC with OASIS vs. 34.9% VBAC without OASIS (OR 2.05, 95% CI 1.31-3.21)].

CONCLUSIONS

Advanced maternal age, increased infant birth weight and an urgent category of initial CS increase the risk of OASIS at VBAC, whereas MLE is protective.

INCREASED OASIS INCIDENCE - INDICATOR OF THE QUALITY OF OBSTETRIC CARE?

In the era of new molecular, epigenetic and proteomic discoveries, birth canal injuries seem like outdated discussion. A vast increase in the incidence of obstetric anal sphincter injuries (OASIS) has been recorded in the last two decades despite advantages in modern medicine and new obstetric methods. This increase might be attributed to the new classification of perineal injury but also to the new imaging methods, including endoanal sonography, which earlier identifies injuries that previously were considered to be occult and actually underwent unrecognized, and which should have been recognized immediately postpartum. OASIS are third and fourth degree perineal injuries that occur during delivery. The reported incidence of OASIS varies from 0.1% to 10.9%. It is well known that third and fourth degree perineal injuries occur more often in primiparae, and in cases of macrosomic newborn, dorsoposterior position of fetal head and shoulder dystocia. The protective role of episiotomy is controversial. Birth canal injury during delivery can happen to any parturient woman. It is important for obstetricians to have this in mind at every delivery. Repercussions of OASIS are serious and can persist for life. They include emotional, psychological, social, physical and sexual disturbances. Therefore, it is very important to recognize the risk factors, diagnose the injury on time and treat it properly by a multidisciplinary team. Accordingly, it can be concluded that the increased incidence of OASIS is a result of better recognition of the risk factors, reduced rates of unrecognized sphincter injuries, adoption of the new classification and better postpartum imagining methods for detection of occult injuries.

Risk factors for obstetric anal sphincter injuries (OASIS) during vacuum extraction delivery in a university affiliated maternity hospital

Introduction: Instrumental delivery is a well-known risk factor for obstetric anal sphincter injuries (OASIS). The specific characteristics among patient undergoing vacuum extraction delivery (VE) are less studied. Therefore, we aimed to evaluate risk factors for OASIS among parturient that underwent a VE delivery in a large university affiliated maternity hospital.Material and methods: The study population contained 9116 women who delivered by VE in tertiary medical center from 1988 to 2015. Inclusion criteria included deliveries beyond 24-week gestation. Multiple gestations and pregnancies complicated with stillbirth were excluded from the analysis. Maternal obstetric variables were compared between parturient with and without OASIS. Independent risk factors for OASIS were assessed by multivariable logistic regression modeling.Results: OASIS was diagnosed in 94 women (1.03%) following vacuum extraction. Among patients who underwent a VE delivery, gravidity and parity were found to be significantly lower in patients with OASIS. A multivariable logistic regression model with OASIS as the outcome variable revealed that among women who underwent VE, while episiotomy and delivery of a macrosomic neonate were not independently associated with OASIS, a strong association between nulliparity and OASIS was found (OR 3.34; 95% CI 1.93-5.78; p < .001).Conclusions: OASIS is uncommon in our population. Vacuum extraction in nulliparous parturient is a significant risk factor for OASIS. Our results should be taken into account when managing nulliparous deliveries.

Obstetric Anal Sphincter Injuries (OASIs) in Israel: A Review of the Incidence and Risk Factors

Obstetric anal sphincter injuries (OASIs) following vaginal deliveries are the main reason for subsequent development of anal incontinence in women. The diagnosis of such tears is crucial for treating and preventing such a grave sequela. The reported rate of OASIs in Israel was between 0.1% and 0.6%, out of all vaginal births, which is 10-fold lower than that reported in Europe and the United States. Structured hands-on training in repair of OASIs in seven medical centers in Israel significantly increased the detection rate of third-degree perineal tears. The implementation of such programs is crucial for increasing awareness and detection rates of OASIs following vaginal deliveries.