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

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.

Trends in obstetric anal sphincter injury in spontaneous vaginal delivery versus operative vaginal delivery over a 10-year period: Lessons learned

OBJECTIVE

To evaluate trends in the incidence of women with obstetric anal sphincter injuries (OASIS) over a 10-year period comparing spontaneous vaginal delivery (SVD) and operative vaginal delivery (OVD).

METHODS

A retrospective study was performed in which all women who underwent vaginal delivery over a 10-year period (n = 86 242, 2009-2018) at the Rotunda Hospital were reviewed. The overall incidence of OASIS was compared with incidence rates stratified by parity and type of vaginal birth.

RESULTS

The 10-year vaginal delivery rate was 69% (n = 59 187) where 24 580 women (42%) were primiparous and 34 607 women (58%) were multiparous. SVD rate was 74% and OVD rate was 26%. The overall incidence of OASIS was 2.9%. The incidence of OASIS in OVD was 5.5% and the incidence in SVD was 2%. Of 498 multipara who sustained OASIS, 366 (73%) had an SVD without episiotomy compared with 14 (3%) who had an episiotomy. There was a significant reduction of OASIS over the 10-year period in primipara who had an OVD but no reduction in the other groups.

CONCLUSION

The primiparous OVD group had a significant reduction of OASIS. Continued education around perineal protection and episiotomy at SVD could positively impact further reduction in OASIS, particularly in the SVD groups.

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.

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.

High Incidence of Obstetric Anal Sphincter Injuries among Immigrant Women of Asian Ethnicity

(1) Background: Obstetric anal sphincter injuries (OASI) may complicate vaginal deliveries. The aim of the present study was to explore the incidence and clinical characteristics of OASI among Asian women living in a Western country compared to local Caucasian women. (2) Methods: A retrospective cohort study of 380 women diagnosed with OASI, following singleton vaginal deliveries, during a 10-year period (January 2011 to December 2020). Exclusion criteria: age < 18 years, stillbirth, and breech presentation. Demographic, clinical, and obstetrical data were obtained, and a comparison between Asian and Caucasian women was performed. (3) Results: There were 35 cases of OASI among 997 women of Asian ethnicity compared to 345 cases of OASI among 86,250 Caucasian women (3.5% vs. 0.4%, respectively, p < 0.001). Asian women endured a significantly higher rate of fourth-degree OASI (17.1%) even though they bore smaller newborns (3318 g vs. 3501 g, p = 0.004), and birth weights rarely exceeded 3800 g (2.8% vs. 25.8%, p < 0.001). Asian ethnicity was also associated with a significantly higher risk for blood transfusion following OASI and a lower tendency for postpartum follow up. (4) Conclusions: Immigrant women of Asian ethnicity had a nine-fold higher rate of OASI, much higher than previously reported. Furthermore, Asian women had higher rates of fourth-degree OASI.

Influence of previous delivery mode on perineal trauma risk

OBJECTIVE

To evaluate the impact of a previous pregnancy and delivery on perineal trauma rates in the subsequent vaginal birth.

METHODS

Retrospective cohort study. The perineal outcomes of secundiparous women with history of previous (first) delivery in one of three categories: failed operative vaginal delivery (FOVD) and second-stage emergency cesarean section (EmCS); elective cesarean section (ElCS), and vaginal delivery (VD) with intact perineum, were compared with a control primiparous group.

RESULTS

The percentage obstetric anal sphincter injuries (OASIS)at first vaginal delivery was 17.3% (n = 9) after previous FOVD+EmCS, 12.9% (n = 18) after previous ElCS, and 0.6% (n = 9) after previous VD maintaining an intact perineum, compared with 6% (n = 1193) in the control primiparous group of women. Multivariate regression analysis demonstrated that previous FOVD+EmCS and ElCS were associated with a statistically significant increased risk of OASIS of 180% and 110% when compared with control (odds ratio [OR] 2.80; 95% confidence interval [CI] 1.35-5.78 and OR 2.10; 95% CI 1.27-3.48, respectively). Previous VD with intact perineum was associated with a statistically significantly reduced risk of OASIS (OR 0.09; 95% CI 0.04-0.17).

CONCLUSIONS

Previous FOVD+EmCS and ElCS were associated with increased risk of OASIS in subsequent vaginal delivery compared with control, whereas previous VD with intact perineum was associated with decreased risk.

Planned mode of birth after previous cesarean section and risk of undergoing pelvic floor surgery: A Scottish population-based record linkage cohort study

BACKGROUND

The global rise in cesarean sections has led to increasing numbers of pregnant women with a history of previous cesarean section. Policy in many high-income settings supports offering these women a choice between planned elective repeat cesarean section (ERCS) or planned vaginal birth after previous cesarean (VBAC), in the absence of contraindications to VBAC. Despite the potential for this choice to affect women's subsequent risk of experiencing pelvic floor disorders, evidence on the associated effects to fully counsel women is lacking. This study investigated the association between planned mode of birth after previous cesarean section and the woman's subsequent risk of undergoing pelvic floor surgery.

METHODS AND FINDINGS

A population-based cohort study of 47,414 singleton term births in Scotland between 1983 to 1996 to women with 1 or more previous cesarean sections was conducted using linked Scottish national routine datasets. Cox regression was used to investigate the association between planned as well as actual mode of birth and women's subsequent risk of having any pelvic floor surgery and specific types of pelvic floor surgery adjusted for sociodemographic, maternal medical, and obstetric-related factors. Over a median of 22.1 years of follow-up, 1,159 (2.44%) of the study population had pelvic floor surgery. The crude incidence rate of any pelvic floor surgery per 1,000 person-years was 1.35, 95% confidence interval (CI) 1.27 to 1.43 in the overall study population, 1.75, 95% CI 1.64 to 1.86 in the planned VBAC group and 0.66, 95% CI 0.57 to 0.75 in the ERCS group. Planned VBAC compared to ERCS was associated with a greater than 2-fold increased risk of the woman undergoing any pelvic floor surgery (adjusted hazard ratio [aHR] 2.38, 95% CI 2.03 to 2.80, p < 0.001) and a 2- to 3-fold increased risk of the woman having surgery for pelvic organ prolapse or urinary incontinence (aHR 3.17, 95% CI 2.47 to 4.09, p < 0.001 and aHR 2.26, 95% CI 1.79 to 2.84, p < 0.001, respectively). Analysis by actual mode of birth showed these increased risks were only apparent in the women who actually had a VBAC, with the women who needed an in-labor non-elective repeat cesarean section having a comparable risk of pelvic floor surgery to those who had an ERCS. The main limitation of this study is the potential for misclassification bias.

CONCLUSIONS

This study suggests that among women with previous cesarean section giving birth to a singleton at term, planned VBAC compared to ERCS is associated with an increased risk of the woman subsequently undergoing pelvic floor surgery including surgery for pelvic organ prolapse and urinary incontinence. However, these risks appear to be only apparent in women who actually give birth vaginally as planned, highlighting the role of vaginal birth rather than labor in pelvic floor dysfunction requiring surgery. The findings provide useful additional information to counsel women with previous cesarean section about the risks and benefits associated with their future birth choices.

Planned mode of birth after previous cesarean section: A structured review of the evidence on the associated outcomes for women and their children in high-income setting

In many high-income settings policy consensus supports giving pregnant women who have had a previous cesarean section a choice between planning an elective repeat cesarean section (ERCS) or planning a vaginal birth after previous cesarean (VBAC), provided they have no contraindications to VBAC. To help women make an informed decision regarding this choice, clinical guidelines advise women should be counseled on the associated risks and benefits. The most recent and comprehensive review of the associated risks and benefits of planned VBAC compared to ERCS in high-income settings was published in 2010 by the US Agency for Healthcare Research and Quality (AHRQ). This paper describes a structured review of the evidence in high-income settings that has been published since the AHRQ review and the literature in high-income settings that has been published since 1980 on outcomes not included in the AHRQ review. Three databases (MEDLINE, EMBASE, and PsycINFO) were searched for relevant studies meeting pre-specified eligible criteria, supplemented by searching of reference lists. Forty-seven studies were identified as meeting the eligibility criteria and included in the structured review. The review suggests that while planned VBAC compared to ERCS is associated with an increased risk of various serious birth-related complications for both the mother and her baby, the absolute risk of these complications is small for either birth approach. The review also found some evidence that planned VBAC compared to ERCS is associated with benefits such as a shorter length of hospital stay and a higher likelihood of breastfeeding. The limited evidence available also suggests that planned mode of birth after previous cesarean section is not associated with the child’s subsequent risk of experiencing adverse neurodevelopmental or health problems in childhood. This information can be used to manage and counsel women with previous cesarean section about their subsequent birth choices. Collectively, the evidence supports existing consensus that there are risks and benefits associated with both planned VBAC and ERCS, and therefore women without contraindications to VBAC should be given an informed choice about planned mode of birth after previous cesarean section. However, further studies into the longer-term effects of planned mode of birth after previous cesarean section are needed along with more research to address the other key limitations and gaps that have been highlighted with the existing evidence.

Obstetric anal sphincter injuries-Maternal, fetal and sociodemographic risk factors: A retrospective register-based study

INTRODUCTION

Obstetric anal sphincter injuries (OASIS) are severe complications to vaginal births with potentially serious long-term consequences and large impact on quality of life. The aim was to determine risk and protective factors for OASIS.

MATERIAL AND METHODS

We performed a retrospective register-based observational study. A cohort of 988 988 singleton term deliveries 2005-2016 in Sweden were included. Data from the Swedish Medical Birth Registry and Statistics Sweden were extracted to identify cases of OASIS and maternal and fetal characteristics. Modified Poisson Regression analyses were performed to assess risk factors.

RESULTS

The rate of OASIS was 3.5% (n = 34 583). Primiparity (adjusted risk ratio [aRR] 3.13, 95% CI 3.05-3.21), vacuum extraction (aRR 2.79, 95% CI 2.73-2.86), forceps (aRR 4.27, 95% CI 3.86-4.72), and high birthweight (aRR 2.61, 95% CI 2.50-2.72) were associated with a significantly increased risk of OASIS. Increasing maternal age and decreasing maternal height also increased the risk of OASIS. Obesity increased the risk of OASIS (aRR 1.04, 95% CI 1.04-1.08), if fetal birthweight was not adjusted for. Smoking (aRR 0.74, 95% CI 0.70-0.79) and low maternal education (aRR 0.87, 95% CI 0.83-0.92) were associated with a decreased frequency of reported OASIS. Previous cesarean section increased the risk of OASIS (aRR 1.41, 95% CI 1.36-1.47).

CONCLUSIONS

Primiparity, instrumental delivery, and high birthweight significantly increased the risk of OASIS. Obesity, low height, increasing age, and previous cesarean section also increased the risk whereas smoking and low maternal educational level were associated with a lower OASIS rate.

A step towards better audit: The Robson Ten Group classification system for outcomes other than cesarean section

INTRODUCTION

The Robson Ten Group Classification System is widely used for the audit of cesarean section (CS) rates. However, CS rate alone is a poor quality indicator and should be balanced with other obstetric endpoints. The aim of this study was to evaluate whether Swedish national data on obstetric outcomes other than CS, stratified by the Robson classification, could be analyzed in a useful way.

MATERIAL AND METHODS

All births in Sweden from 2017 through 2020 recorded in the nationwide Swedish Pregnancy Register were categorized using the Robson classification with subdivision of some groups. Five outcomes were explored: CS, operative vaginal delivery, postpartum hemorrhage, obstetric anal sphincter injury (OASIS) and Apgar score <7 at 5 minuteutes. Rates of each outcome and contribution of each group to the total outcome rate were calculated.

RESULTS

The largest Robson groups were nulliparous and multiparous women with single-term cephalic pregnancies, unscarred uterus and spontaneous labor. Intrapartum CS rates were highest for multiple pregnancies, women with induced labor after previous CS, and nulliparous women with induced labor. Nulliparous women and multiparous women with a previous CS with attempted vaginal birth had the highest operative vaginal delivery and OASIS rates. The postpartum hemorrhage rate was highest for multiple pregnancies and transverse lie, followed by prelabor CS in nulliparous and multiparous women with single-term cephalic pregnancies and unscarred uterus. The highest rates of Apgar score <7 at 5 minute were observed in preterm deliveries, multiple pregnancies, transverse lie and breech presentation. The largest contribution to the total CS rate was made by women with previous CS delivered by prelabor CS, and nulliparous women with induced or spontaneous labor. The largest contribution to all other outcomes was made by nulliparous women with spontaneous or induced labor and, notably, multiparous women with spontaneous labor and unscarred uterus.

CONCLUSIONS

The Robson classification provides a useful framework for analyzing CS rates along with rates of operative vaginal delivery, OASIS, postpartum hemorrhage and low Apgar score. Parallel interpretation of several outcomes allows a systematic and multidimensional audit, helpful for families and healthcare professionals, and can be used for comparisons, assessment of trends and subpopulations.

Risk of obstetric anal sphincter injuries at the time of admission for delivery: A clinical prediction model

OBJECTIVE

To develop and validate a model to predict obstetric anal sphincter injuries (OASIS) using only information available at the time of admission for labour.

DESIGN

A clinical predictive model using a retrospective cohort.

SETTING

A US health system containing one community and one tertiary hospital.

SAMPLE

A total of 22 873 pregnancy episodes with in-hospital delivery at or beyond 21 weeks of gestation.

METHODS

Thirty antepartum risk factors were identified as candidate variables, and a prediction model was built using logistic regression predicting OASIS versus no OASIS. Models were fit using the overall study population and separately using hospital-specific cohorts. Bootstrapping was used for internal validation and external cross-validation was performed between the two hospital cohorts.

MAIN OUTCOME MEASURES

Model performance was estimated using the bias-corrected concordance index (c-index), calibration plots and decision curves.

RESULTS

Fifteen risk factors were retained in the final model. Decreasing parity, previous caesarean birth and cardiovascular disease increased risk of OASIS, whereas tobacco use and black race decreased risk. The final model from the total study population had good discrimination (c-index 0.77, 95% confidence interval [CI] 0.75-0.78) and was able to accurately predict risks between 0 and 35%, where average risk for OASIS was 3%. The site-specific model fit using patients only from the tertiary hospital had c-stat 0.74 (95% CI 0.72-0.77) on community hospital patients, and the community hospital model was 0.77 (95%CI 0.76-0.80) on the tertiary hospital patients.

CONCLUSIONS

OASIS can be accurately predicted based on variables known at the time of admission for labour. These predictions could be useful for selectively implementing OASIS prevention strategies.

Is there an Association between Vaginal Birth after Cesarean Prediction and Obstetric Anal Sphincter Injury?

OBJECTIVE

This study aimed to estimate whether there is an association between the predicted probability of vaginal birth after cesarean delivery (VBAC) and the occurrence of obstetric anal sphincter injuries (OASIS).

STUDY DESIGN

This was a single-site retrospective cohort study of all women with a singleton vaginal birth after a previous cesarean section between January 2011 and December 2016. Women were divided into four ordinal groupings by the predicted probability of achieving vaginal birth after cesarean using the Maternal-Fetal Medicine Units Network VBAC calculator (less than 41%, 40.1-60%, 60.1-80%, and greater than 80%). The primary outcome was OASIS, defined as a 3rd or 4th degree perineal laceration. Bivariable and multivariable analyses were used to examine the association between predicted VBAC probability and OASIS.

RESULTS

In total, 1,411 women met inclusion criteria and 73 (5.2%) sustained OASIS. The median predicted probability of VBAC was lower in women with OASIS compared with those without OASIS (60% [interquartile range {IQR}: 48-70%] vs. 66% (IQR: 52-80%), p = 0.02]. On bivariable and multivariable logistic regression, predicted probability of VBAC was associated with increased odds of OASIS (less than 41% probability: adjusted odds ratio [aOR]: 3.18, 95% confidence interval [CI]: 0.90-11.21; 41-60% probability: aOR: 3.76, 95% CI: 1.34-10.57; 61-80% probability aOR: 3.47, 95% CI: 1.25-9.69) relative to women with a predicted probability of VBAC of greater than 80%.

CONCLUSION

Having a lower predicted probability of VBAC is associated with an increased risk of OASIS at the time of a VBAC relative to those with greater than 80% predicted probability. Incorporation of this aspect of maternal morbidity may inform risk-stratification at the time of trial of labor after cesarean, as well as the choice of performing an operative vaginal delivery.

KEY POINTS

· Predicted probability of VBAC is associated with OASIS.. · Low predicted probability of VBAC is associated with increased odds of OASIS.. · Forceps delivery was associated with the highest odds of OASIS..

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.

Temporal trends in obstetric anal sphincter injury from the first vaginal delivery in Austria, Canada, Norway, and Sweden

INTRODUCTION

Obstetric anal sphincter injuries (OASI) are severe complications that can cause considerable short- and long-term morbidity. Austria, Canada, Norway, and Sweden have similar socio-economic characteristics, and all four countries have access to national birth registers. In this study, we hypothesized that the incidence of OASI should be very similar for different obstetric scenarios in these four countries. Therefore, the aim was to compare the incidence of OASI in these four countries in primiparous women, with spontaneous or instrumental delivery (vacuum or forceps), and in women with a first vaginal birth after cesarean section (VBAC).

MATERIAL AND METHODS

Aggregated data on 1 933 930 vaginally delivered primiparous women and women with VBAC were retrieved from the birth registers gathered in Austria, Canada, Norway, and Sweden. The annual rate of OASI (ICD-10 codes O70.2-O70.3) was presented as the percentage of women with a spontaneous delivery, vacuum or forceps delivery, and a VBAC during the period 2004-2016.

RESULTS

The incidence of OASI varied considerably between countries and over time. Canada and Sweden had the highest rates, and Austria and Norway the lowest. In Norway, the rate of OASI decreased consistently for all types of deliveries after introducing a perineal protection program in 2004 (p < 0.001). During vacuum delivery, the incidence of OASI varied between countries from 4.1% to 15.5% across the study period. In Canada and Norway, the rate of OASI after a forceps delivery was similar in 2004 at ~20% and with differing trajectories to 24.3% (β 0.49) and 6.2% (β -1.15) (trend, all p < 0.001) in 2016.

CONCLUSIONS

This comparative register study suggests that there may be considerable potential for lowering the incidence of OASI. The perineal protection program implemented by Norway has been successful. Each country should critically, without prejudice, analyze their current clinical practices and rate of OASI and consider the best preventive strategy.

Pelvic floor dysfunction in primiparous women up to 6 months after delivery: cohort study

OBJECTIVE

To analyze pelvic floor muscular strength (PFMS), urinary (UI) and anal (AI) incontinence and dyspareunia in primiparous women up to 6 months after normal or cesarean delivery.

METHODS

this is a prospective cohort with 169 women (128 normal births, 41 cesarean sections), followed between 50-70 and 170-190 days postpartum, when PFMS was measured using perineometry, and UI and AI and dyspareunia, through interview.

RESULTS

PFMS, UI and dyspareunia were similar between types of delivery. The difference was significant only for the time elapsed, with improvement in the studied period (2 and 6 months postpartum). Regarding AI, there was a significant difference between 2 and 6 months postpartum, with an interaction between type of delivery and time (p=0.022).

CONCLUSION

the type of delivery did not show any influence on pelvic floor dysfunctions, except for AI. For all outcomes, there was an improvement in the period studied.

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.

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.

Safety and feasibility of trial of vaginal labor after cesarean section: A retrospective study

By observing and analyzing the success rate of Tai'an City central hospital TOLAC and VBNC and various indicators after delivery, we make sure whether TOLAC is safe and feasible to be promoted in Tai'an area.Between January and December 2017, data of 144 cases undergoing TOLAC, 152 cases undergoing VBNC, 152 cases undergoing RCS and 142 case undergoing PCS in Tai'an City Central Hospital were retrospectively analyzed. The success rate of vaginal delivery, labor time, 24 hours postpartum hemorrhage, hospital stay, Apgar score of newborns and puerperal morbidity were observed.Primary study outcomes: The success rates of the TOLAC and VBNC groups were 93.06% and 93.42%, respectively, where the difference was not statistically significant (P = .901). Secondary study outcomes: There were no significant differences in labor time (P = .0249), amount of 24 hours postpartum hemorrhage (P = .206), Apgar score of newborns (P = .582), hospital stay (P = .194) and puerperal morbidity (P = .942) between the VBAC group and VBNC group. There were statistically significant differences in amount of 24 hours postpartum hemorrhage (P < .001), hospital stay (P < .001) and puerperal morbidity (P = .018), but no difference in Apgar score of newborns (P = .228) between the VBAC group and RCS group. There were significant differences in operation time (P = .011), amount of 24 hours hemorrhage (P = .001), hospital stay (P = .001) and puerperal morbidity (P = .041), but no significant difference in Apgar score of newborns (P = .300) between the RCS and PCS groups.The TOLAC is as safe and feasible as VBNC, and more favorable to the safety of mother and fetus than RCS in Tai'an area.

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

BACKGROUND

Obstetrical anal sphincter injuries are an important complication of vaginal deliveries that may result in short- and long-term pelvic floor morbidity and a diminished quality of life in young, healthy women. The prevalence of obstetrical anal sphincter injuries ranges from 0.1% to 8.7%. Over recent years, there seems to be a trend of increasing occurrence of obstetrical anal sphincter injuries worldwide. It is unclear why the rates are rising. Previous studies have examined the effect of different risk factors on the prevalence of obstetrical anal sphincter injuries. The change in the incidence of some risk factors for obstetrical anal sphincter injuries can partially explain the overall increase in obstetrical anal sphincter injuries. There is no previous study that explored the impact of the changes of individual risk factors over time on the risk for obstetrical anal sphincter injuries.

OBJECTIVE

The main aim of this study was to examine the temporal trends in the prevalence and odds ratio of the major risk factors known to be associated with obstetrical anal sphincter injuries in the period from 1988 to 2016.

STUDY DESIGN

This was a retrospective cohort study that included all women who underwent vaginal deliveries between 1988 and 2016 at a tertiary university medical center. The time intervals were divided into 4 periods (1988-1997, 1998-2007, 2008-2016, and the total time from 1988 to 2016) and the incidence of each risk factor was calculated for each time period. Correlation models and regression analysis were performed to examine the association between obstetrical anal sphincter injuries and the different risk factors over time. Furthermore, the trends in the odds ratios of the important risk factors over the time periods were evaluated using a multivariate regression analysis in which the primiparous women were separated from the multiparous women.

RESULTS

During the study period, there were 295,668 vaginal deliveries. Of these, 591 women were diagnosed with obstetrical anal sphincter injuries (0.2%). The significant risk factors for obstetrical anal sphincter injuries (P<.05) in the multivariable analysis were the following: primiparity, vaginal birth after cesarean delivery, vacuum extraction, and a birthweight of >4 kg. There was a significant (P<.05) increase in the incidence over the study period for the following risk factors: primiparity, vaginal birth after cesarean delivery, and vacuum extraction. No change was found in the incidence of the risk factor of a birthweight of >4 kg. In addition, we found a strengthening of the association between vaginal birth after cesarean delivery and macrosomia with obstetrical anal sphincter injuries, as opposed to a decline in the relative contribution of vacuum extraction to the overall risk for obstetrical anal sphincter injuries. Moreover, we found that obstetrical anal sphincter injuries among primiparous women increased 7-fold over the study period but was unchanged among multiparous women.

CONCLUSION

We have shown significant (P<.05) temporal trends in the incidence and odds ratio of some of the known risk factors for obstetrical anal sphincter injuries. A better understanding of the changes in the incidence and specific contribution of important risk factors for obstetrical anal sphincter injuries may explain, in part, the worldwide increase in the prevalence of this important and detrimental complication of vaginal birth.

Maternal Ethnicity and the Risk of Obstetrical Anal Sphincter Injury: A Retrospective Cohort Study

OBJECTIVE

To explore the role of maternal ethnicity as a risk factor for obstetrical anal sphincter injury (OASI).

METHODS

A retrospective cohort study of all women with singleton gestations who had a vaginal delivery at term, between January 2014 and October 2017, at a single center. OASI was defined as a third-degree perineal tear (anal sphincter complex) or a fourth-degree perineal tear (anorectal mucosa). The characteristics of women with and without OASIs were compared. Multiple logistic regression was performed to account for potential confounders, including ethnicity.

RESULTS

During the study period, 11 012 women were eligible for inclusion, of whom 336 (3.1%) had an OASI; 313 (93.1%) had a third-degree tear, and 23 (6.9%) had a fourth-degree tear. Women with OASIs were characterized by younger maternal age (<35 years), Asian ethnicity, nulliparity, neonatal birth weight ≥3500 grams, midline and mediolateral episiotomy, second stage of labour lasting ≥60 minutes, and assisted vaginal delivery. After adjusting for potential confounders, Asian ethnicity remained independently associated with increased risk of OASI (adjusted odds ratio 2.07; 95% CI 1.6-2.7) whereas mediolateral episiotomy was independently associated with decreased risk of OASI (adjusted odds ratio 0.64; 95% CI 0.5-0.9).

CONCLUSION

Asian ethnicity is independently associated with increased risk of OASI. Although midline episiotomy increases the risk of OASI, mediolateral episiotomy may protect against OASI, and should be considered in high-risk patients.