A prior cesarean section and incidence of obstetric anal sphincter injury

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.

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.

Effect of the length of the second stage of labor on pelvic floor dysfunction

BACKGROUND

Pelvic floor dysfunction refers to any combination of incontinence, overactive bladder, pelvic organ prolapse, and sexual dysfunction. Pelvic floor dysfunction affects approximately 25% to 30% of women and is linked to parity and age. Some obstetrical risk factors have been highlighted, though the second stage of labor has not been as thoroughly investigated. Allowing a longer second stage has been suggested as a method of reducing the rates of cesarean delivery in nulliparous women, though it has also been linked to pelvic floor injuries.

OBJECTIVE

This study aimed to determine the effect of the length of the second stage of labor on self-reported pelvic floor dysfunction.

STUDY DESIGN

This was a single-center prospective cohort study in a tertiary referral obstetrical unit. Nulliparous women attending routine antenatal clinics were recruited to complete the Australian Pelvic Floor Questionnaire during pregnancy and again 3 months after delivery. The primary outcome in this study was the effect of the length of the second stage of labor on total pelvic floor scores when analyzed using multiple regression. The models were adjusted for the mother's age, mother's body mass index, length of the second stage of labor, fetal birthweight, mode of delivery, and perineal trauma. The secondary outcomes included the comparison of maternal, obstetrical, and functional pelvic floor outcomes based on the mode of delivery and the length of the second stage of labor.

RESULTS

Among the 295 women who were recruited, the length of the second stage of labor and body mass index were associated with self-reported bladder dysfunction on multiple regression, whereas maternal age was protective. Compared with those with 60 to 120 minutes or <60 minutes of second stage of labor, women with that longer than 120 minutes had higher rates of stress incontinence (85.7% [>120 minutes] vs 41.7% [60-120 minutes] or 52.5% [<60 minutes], P=.001), urinary urgency (89.3% [>120 minutes] vs 39.6% [60-120 minutes] or 53.8% [<60 minutes], P<.001), and fecal incontinence (10.7% [>120 minutes] vs 0% [60-120 minutes] or 1.2% [<60 minutes], P=.027). There were no differences in the rates of sexual activity or dyspareunia. Women delivering vaginally had higher rates of stress incontinence (57.6% vs 38.0%, P=.006) than those undergoing cesarean delivery, though there were no differences in other pelvic floor symptoms or pelvic floor scores.

CONCLUSION

A prolonged second stage of labor is associated with more self-reported bladder dysfunction at 3 months postnatal in primiparous women. Women with a longer second stage of labor should be informed about the risk of short-term bladder dysfunction, though the prevalence of long-term sequelae is unknown.

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: 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.

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..

The effect of two midwives during the second stage of labour to reduce severe perineal trauma (Oneplus): a multicentre, randomised controlled trial in Sweden

BACKGROUND

Severe perineal trauma (SPT) affecting the anal sphincter muscle complex is a serious complication following childbirth, associated with short-term and long-term maternal morbidity. Effective preventive strategies are still scarce. The aim of the Oneplus trial was to test the hypothesis that the presence of a second midwife during the second stage of labour, with the purpose of preventing SPT, would result in fewer injuries affecting the anal sphincter than if attended by one midwife.

METHODS

In this multicentre, randomised, controlled parallel group, unmasked trial done at five obstetric units in Sweden, women were randomly assigned to be assisted by either one or two midwives in late second stage. Nulliparous women and women planning the first vaginal birth after caesarean section who were age 18-47 years were randomly assigned to an intervention when reaching the second stage of labour. Further inclusion criteria were gestational week 37+0, carrying a singleton live fetus in vertex presentation, and proficiency in either Swedish, English, Arabic, or Farsi. Exclusion criteria were a multiple pregnancy, intrauterine fetal demise, a planned caesarean section, or women who were less than 37 weeks pregnant. Randomisation to the intervention group of two midwives or standard care group of one midwife (1:1) was done using a computer-based program and treatment groups were allocated by use of sealed opaque envelopes. All women and midwives were aware of the group assignment, but the statistician from Clinical Studies Forum South, who did the analyses, was masked to group assignment. Midwives were instructed to implement existing prevention models and the second midwife was to assist on instruction of the primary midwife, when asked. Midwives were also instructed to complete case report forms detailing assistance techniques and perineal trauma prevention techniques. The primary outcome was the proportion of women who had SPT, for which odds ratios (ORs) and 95% CIs were calculated, and logistic regression was done to adjust for study site. All analyses were done according to intention to treat. The trial is registered with ClinicalTrials.gov, NCT0377096.

FINDINGS

Between Dec 10, 2018, and March 21, 2020, 8866 women were assessed for eligibility, and 4264 met the inclusion criteria and agreed to participate. 3776 (88·5%) of 4264 women were randomly assigned to an intervention after reaching the second stage of labour. 1892 women were assigned to collegial assistance (two midwives) during the second stage of labour and 1884 women were assigned to standard care (one midwife). 13 women in each group did not meet the inclusion criteria and were excluded. After further exclusions, 1546 women spontaneously gave birth in the intervention group and 1513 in the standard care group. 1546 women in the intervention group and 1513 in the standard care group were included in the intention-to-treat analysis of the primary outcome. There was a significant reduction in SPT in the intervention group (3·9% [61 of 1546] vs 5·7% [86 of 1513]; adjusted OR 0·69 (0·49-0·97).

INTERPRETATION

The presence of two midwives during the active second stage can reduce SPT in women giving birth for the first time.

FUNDING

The Swedish Research Council for Health, Working Life and Welfare; Jan Hains Research Foundation; and Skane County Council's Research and Development Foundation.

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.

Predicting obstetrical anal sphincter injuries in patients who undergo vaginal birth after cesarean delivery

BACKGROUND

Women with a history of previous cesarean delivery must weigh the numerous potential risks and benefits of elective repeat cesarean delivery or trial of labor after cesarean delivery. Notably, 1 important risk of vaginal delivery is obstetrical anal sphincter injuries. Furthermore, the rate of obstetrical anal sphincter injuries is high among women undergoing vaginal birth after cesarean delivery. However, the risk of obstetrical anal sphincter injuries is not routinely included in the trial of labor after cesarean delivery counseling, and there is no tool available to risk stratify obstetrical anal sphincter injuries among women undergoing vaginal birth after cesarean delivery.

OBJECTIVE

This study aimed to develop and validate a predictive model to estimate the risk of obstetrical anal sphincter injuries in the setting of vaginal birth after cesarean delivery population to improve antenatal counseling of patients regarding risks of trial of labor after cesarean delivery.

STUDY DESIGN

This study was a secondary subgroup analysis of the Maternal-Fetal Medicine Units Network Trial of Labor After Cesarean Delivery prospective cohort (1999-2002). We identified women within the Maternal-Fetal Medicine Units Network cohort with 1 previous cesarean delivery followed by a term vaginal birth after cesarean delivery. This Maternal-Fetal Medicine Units Network Vaginal Birth After Cesarean Delivery cohort was stratified into 2 groups based on the presence of obstetrical anal sphincter injuries, and baseline characteristics were compared with bivariate analysis. Significant covariates in bivariate testing were included in a backward stepwise logistic regression model to identify independent risk factors for obstetrical anal sphincter injuries and generate a predictive model for obstetrical anal sphincter injuries in the setting of vaginal birth after cesarean delivery. Internal validation was performed using bootstrapped bias-corrected estimates of model concordance indices, Brier scores, Hosmer-Lemeshow chi-squared values, and calibration plots. External validation was performed using data from a single-site retrospective cohort of women with a singleton vaginal birth after cesarean delivery from January 2011 to December 2016.

RESULTS

In this study, 10,697 women in the Maternal-Fetal Medicine Units Network Trial of Labor After Cesarean Delivery cohort met the inclusion criteria, and 669 women (6.3%) experienced obstetrical anal sphincter injuries. In the model, factors independently associated with obstetrical anal sphincter injuries included use of forceps (adjusted odds ratio, 5.08; 95% confidence interval, 4.10-6.31) and vacuum assistance (adjusted odds ratio, 2.64; 95% confidence interval, 2.02-3.44), along with increasing maternal age (adjusted odds ratio, 1.05; 95% confidence interval, 1.04-1.07 per year), body mass index (adjusted odds ratio, 0.99; 95% confidence interval, 0.97-1.00 per unit kg/m²), previous vaginal delivery (adjusted odds ratio, 0.19; 95% confidence interval, 0.15-0.23), and tobacco use during pregnancy (adjusted odds ratio, 0.59; 95% confidence interval, 0.43-0.82). Internal validation demonstrated appropriate discrimination (concordance index, 0.790; 95% confidence interval, 0.771-0.808) and calibration (Brier score, 0.047). External validation used data from 1266 women who delivered at a tertiary healthcare system, with appropriate model discrimination (concordance index, 0.791; 95% confidence interval, 0.735-0.846) and calibration (Brier score, 0.046). The model can be accessed at oasisriskscore.xyz.

CONCLUSION

Our model provided a robust, validated estimate of the probability of obstetrical anal sphincter injuries during vaginal birth after cesarean delivery using known antenatal risk factors and 1 modifiable intrapartum risk factor and can be used to counsel patients regarding risks of trial of labor after cesarean delivery compared with risks of elective repeat cesarean delivery.

Vaginal birth after Cesarean section and levator ani avulsion: a case-control study

OBJECTIVE

The aim of this study was to explore the risk of levator ani muscle (LAM) avulsion and enlargement of the levator hiatus following vaginal birth after Cesarean section (VBAC) in comparison with vaginal delivery in primiparous women.

METHODS

In this two-center observational case-control study, we identified all women who had a term VBAC for their second delivery at the Departments of Obstetrics and Gynecology at the Faculty of Medicine in Pilsen and the 1^st Faculty of Medicine in Prague, Charles University, Czech Republic, between 2012 and 2016. Women with a repeat VBAC, preterm birth or stillbirth were excluded from the study. As a control group, we enrolled a cohort of primiparous women who delivered vaginally during the study period. To increase our control sample, we also invited all primiparous women who delivered vaginally in both participating units between May and June 2019 to participate. All participants were invited for a four-dimensional pelvic floor ultrasound scan to assess LAM trauma. LAM avulsion and the area of the levator hiatus were assessed offline from the stored pelvic floor volumes obtained at rest, during maximum contraction and during Valsalva maneuver. The laterality of the avulsion was also noted. The cohorts were then compared using the χ² test and Wilcoxon's two-sample test according to the normality of the distribution. P < 0.05 was considered statistically significant. Multivariate regression analysis, controlling for age and body mass index (BMI), was also performed.

RESULTS

A total of 356 women had a VBAC for their second delivery during the study period. Of these, 152 (42.7%) attended the ultrasound examination and full data were available for statistical analysis for 141 women. The control group comprised 113 primiparous women. A significant difference was observed between the VBAC group and the control group in age (32.7 vs 30.1 years; P < 0.05), BMI (28.4 vs 27.4 kg/m² ; P < 0.05) and duration of the first and second stages of labor (293.1 vs 345.9 min; P < 0.05 and 27.6 vs 35.3 min; P < 0.05, respectively) at the time of the index birth. The LAM avulsion rate was significantly higher in the VBAC compared with the control group (32.6% vs 18.6%; P = 0.01). The difference between the groups was observed predominantly in the rate of unilateral avulsion and remained significant after controlling for age and BMI (adjusted odds ratio 2.061 (95% CI, 1.103-3.852)). There was no statistically significant difference in the area of the levator hiatus at rest (12.0 vs 12.6 cm² ; P = 0.28) or on maximum Valsalva maneuver (18.6 vs 18.7 cm² ; P = 0.55) between the VBAC and control groups. The incidence of levator hiatal ballooning was comparable between the groups (17.7% and 18.6%; P = 0.86).

CONCLUSIONS

VBAC is associated with a significantly higher rate of LAM avulsion than is vaginal birth in nulliparous women. The difference was significant even after controlling for age and BMI. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Short statured primigravidae: Options for the obstetric management from a survey of UK obstetricians

OBJECTIVE

To assess the current antenatal and intrapartum management options for primigravid women of short stature with a clinically large fetus by a survey of UK Obstetricians.

STUDY DESIGN

An online survey comprised of 15 questions including the options on timing and mode of delivery, counselling about the risk of long-term pelvic floor morbidity following spontaneous vaginal and instrumental deliveries, choice of instruments and the role of episiotomy. The survey was sent to the participants as a part of Royal College of Obstetricians and Gynaecologists (RCOG) Newsletter between September 2017 to October 2018. The scenario described was of a primigravid short stature woman (i.e. height of 160 cm or less) who presents with a clinically large fetus at 38 weeks gestation.

RESULTS

424 Obstetricians participated in the survey. The participation ratio cannot be identified as the survey was emailed as a part of the RCOG Newsletter. Sixty five percent respondents stated that they would scan for estimated fetal weight, 48 % would offer induction of labour at 40 weeks and 14 % would offer an elective/planned caesarean section (CS) at 39-40 weeks. Fifty nine percent would discuss all these risks: obstructed labour, shoulder dystocia, instrumental delivery and obstetric anal sphincter injury (OASI). 73 % would not discuss the long-term risks of urinary and/or faecal incontinence and pelvic organ prolapse. In the presence of failure to progress in the second stage of labour, 69 % would attempt a rotational instrumental delivery and 5% would offer a caesarean section. Manual rotation and 'straight' forceps application were the most frequent type of rotational delivery, followed by Ventouse and Kiellands forceps. Thirty four percent stated that they do not routinely perform an episiotomy in this scenario. Seventy three percent stated that their choice of instrument was not based on the long-term risk of urinary and faecal incontinence.

CONCLUSION

The results suggest that 40 % of the respondents would not discuss all of the complications after vaginal delivery in women of short stature. The most common delivery option would be vaginal delivery.

One Plus One Equals Two-will that do? A trial protocol for a Swedish multicentre randomised controlled trial to evaluate a clinical practice to reduce severe perineal trauma {1}

Background

Severe perineal trauma sustained during childbirth is a serious complication since it can lead to both short- and long-term consequences for women. Some of the methods used to prevent perineal injuries have been evaluated in clinical trials, but there are still gaps in the evidence. A new clinical practice has been introduced, adopted by more than half of the maternity wards in Sweden with the aim of reducing severe perineal trauma. This procedure involves two midwives assisting the woman during the second stage of labour.

Methods/design

In this multicentre randomised controlled trial, 2946 women will be randomised to be assisted by one or two midwives during the second stage of labour. Women age 18–47, who plan for their first vaginal birth, with a singleton pregnancy in cephalic presentation, will be asked to participate when admitted to the maternity ward. Five maternity wards comprising 19,500 births/year in different parts of Sweden will participate in this study. The sample size is powered to demonstrate a 50% reduction (from 4.1–2.0%) in primary outcome, which is the prevalence of severe perineal trauma (3rd and 4th degree). Secondary outcomes will include maternal and neonatal outcomes, women’s experiences, midwives’ experiences of the intervention, incontinence, and pelvic floor symptoms. The primary analysis is intention to treat. Questionnaires will be sent to the women at 1 month and 1 year after the birth to assess women’s experiences, pain, incontinence, pelvic floor symptoms, sexual function, and mental health.

Discussion

It is important for care during labour and birth to be evidence based. There is a strong desire among midwives to reduce the risk of severe perineal trauma. This may lead to new strategies and practices being implemented into practice without scientific evidence. The intervention might have negative side effects or unintended consequences. On the other hand, there is a possibility of the intervention improving care for women.

Trial registration {2a}

ClinicalTrials.gov NCT03770962. Registered on 10 December 2018

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

INTRODUCTION

We wanted to evaluate whether secundiparas who achieved vaginal birth after cesarean (VBAC) were at an increased risk for obstetric anal sphincter injury (OASI) compared to primiparas who delivered vaginally, with a stratification by the mode of delivery-spontaneous or operative vaginal delivery.

MATERIAL AND METHODS

We conducted a retrospective cohort study of primiparous women who delivered by vacuum-assisted delivery between March 2011 and June 2019. Primiparas delivering vaginally and secundiparas undergoing VBAC were compared. The cohort was further stratified into two categories: spontaneous vaginal delivery and operative vaginal delivery.

RESULTS

Overall, 23 822 primiparas who delivered vaginally and 1596 secundiparas who underwent VBAC were analyzed. Operative vaginal delivery was performed in 4561 deliveries. OASI rate did not differ between the VBAC and primipara groups (1.3% vs 1.8%, P = .142). A total of 20 857 women delivered by spontaneous vaginal delivery, among them 1180 (5.7%) women were secundiparas and 19 677 (94.3%) were primiparas. OASI rate was comparable between the secundiparas undergoing VBAC and primiparas delivering vaginally (17 [1.4%] vs 338 [1.7%], P = .436). A total of 4561 women delivered by operative vaginal delivery, among them 416 (9.1%) were secundiparas and 4145 (90.9%) were primiparas. The rate of operative vaginal deliveries was higher among the VBAC group compared with the primipara group (6.1% vs 17.4%, P < .001). However, women undergoing successful VBAC had lower rates of OASI compared with primiparas (3 [0.7%] vs 96 [2.3%]; odds ratio [OR] 0.30, 95% CI 0.09-0.97, P = .032). After multivariate logistic regression including all statistically significant factors, OASI was not associated with VBAC in spontaneous or operative vaginal deliveries (adjusted OR 0.85, 95% CI 0.51-1.40 and 0.39, 95% CI 0.12-1.28, respectively).

CONCLUSIONS

Secundiparas undergoing VBAC were not at a higher risk of OASI when compared with primiparas delivering vaginally, either in spontaneous or operative vaginal deliveries. This information might aid when counseling women contemplating a trial of labor after cesarean--to address their concerns regarding the risks and benefits of VBAC.

Delivery after an obstetric anal sphincter tear

Purpose

The present study aimed to assess the risk of obstetric anal sphincter injuries (OASIS) of a subsequent delivery after the previous OASIS in countries with low (Finland) and high rates (Norway and Sweden) of OASIS.

Methods

This population-based case–control study included women who experienced OASIS 1997–2002. 26,598 women with OASIS were included from countries with low (Finland) and high (Norway and Sweden) OASIS incidences. Each case was matched with one background-adjusted control without OASIS. A follow-up data, including all subsequent deliveries between 1998 and 2011 were then collected. Statistics significances were calculated using chi-square test, test for relative proportions and Students t test, where appropriate.

Results

OASIS in the first birth was associated with increased recurrences in subsequent births, 6.9% vs. 1.7% in Norway (p < 0.001); 4.5% vs. 0.7 (p < 0.001) in Sweden; and 2.1% vs. 0.8% in Finland (p = 0.038). In Norway, more than two deliveries occurred in 4.8% of cases and 6.2% of controls (p = 0.001), 4.2% vs. 5.1% in Sweden (p < 0.001), and 5.7% vs. 6.3% in Finland (p = 0.572). For women with OASIS in a previous delivery, the rates of cesarean deliveries in subsequent pregnancies were 16.4% (7.9% for controls) in Norway, and 16.3% (6.0% for controls) in Sweden, and 50.2% (14.2% for controls) in Finland. In all countries, the differences between cases and controls were significant (p < 0.001).

Conclusion

Next deliveries after OASIS are associated with increased frequency of new OASIS, more cesarean deliveries, and less subsequent deliveries in the high-risk population than women without previous OASIS.

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.

Timing of cesarean and its impact on labor duration and genital tract trauma at the first subsequent vaginal birth: a retrospective cohort study

Background

The objectives of this study were to explore the course of labor and the risk of obstetric anal sphincter injury at the first vaginal birth after cesarean section (fVBAC) in comparison to primiparous vaginal birth (PVB) in women without epidural analgesia and to assess if laboring before the previous cesarean affected these outcomes.

Methods

All fVBACs without epidural analgesia and the subsequent PVBs (controls) between 2012 and 2016 were included in this retrospective cohort study. Data were collected from health records and included maternal demographics, gestational age, and labor details (duration of 1st and 2nd stages, labor induction or augmentation, birthweight, operative vaginal birth, estimated blood loss, extent of childbirth trauma) in both groups as well as cervical dilation at the time of previous cesarean in the fVBAC group. Wilcoxon and Chi-square tests were used for data analyses.

Results

The study comprised 510 women; 255 fVBACs and 255 controls. The majority of fVBACs were after a pre-labor cesarean section – 177 (69.4%). There was a statistically significant difference in the recorded duration of first stage between the fVBACs and controls (289 vs. 347 min respectively, p < .001). Women were less likely to have an intact perineum in the fVBAC group (29.8 vs. 43.1%, p < 0.01), however, there was no statistically significant difference in anal sphincter injury rates between both groups (2.3 vs. 1.9%, p = 0.76). The groups differed in rates of cervical tears requiring suturing (21.2 vs. 12.9%, p = 0.01). On further subgroup analysis, the duration of first stage of labor was shorter in women who previously had a caesarean section late in labor (≥ 8 cm cervical dilatation) compared to a pre-labor cesarean section, however, there were no differences in other outcomes.

Conclusion

Compared to primiparous women having a vaginal birth, women having their first vaginal birth after a cesarean section have a shorter 1st stage of labor (particularly if the cesarean was performed in advanced labor), a higher risk of sustaining cervical lacerations and perineal trauma. However, there was no difference in the risk of sustaining obstetric anal sphincter injuries between the study groups.

Electronic supplementary material

The online version of this article (10.1186/s12884-019-2359-7) contains supplementary material, which is available to authorized users.

Severe perineal trauma among women undergoing vaginal birth after cesarean delivery: A population-based cohort study

BACKGROUND

To examine risk of severe perineal trauma among nulliparous women and those undergoing vaginal birth after cesarean delivery (VBAC).

METHODS

This is a population-based cohort study of all births to women with their two first consecutive singleton pregnancies in Stockholm-Gotland Sweden between 2008 and 2014. Risk of severe perineal trauma was compared between nulliparous women and those undergoing VBAC with severe perineal trauma being the main outcome measure. Associations between indication and timing of primary cesarean delivery and risk of severe perineal trauma in subsequent vaginal birth were analyzed using Poisson regression analysis.

RESULTS

The rate of severe perineal trauma among nulliparous women and those undergoing VBAC was 7.0% and 12.3%, respectively. Compared with nulliparous women, those undergoing VBAC were significantly older, had a shorter stature, and gave birth in a non-upright position to heavier infants with larger head circumferences. The rate of instrumental vaginal delivery among nulliparous women and those undergoing VBAC was 19.3% and 20.2%, respectively (P = 0.331). An increased risk of severe perineal trauma remained after adjustments among those undergoing VBAC (adjusted risk ratio 1.42, 95% CI 1.23-1.63). Level of risk was not associated with indication (dystocia or signs of fetal distress) of primary cesarean delivery, nor how far the woman had progressed in labor (fully dilated versus planned cesarean delivery) before delivering by cesarean.

CONCLUSIONS

Compared with nulliparous women, those undergoing VBAC are at increased risk of severe perineal trauma, irrespective of indication and timing of primary cesarean delivery.

Genital tract tears in women giving birth on a birth seat: A cohort study with prospectively collected data

BACKGROUND

Birth positions may influence the risk of tears in the genital tract during birth. Birth positions are widely studied yet knowledge on genital tract tears following birth on a birth seat is inconclusive.

AIM

The objective of this study was to describe the proportion of genital tract tears in women who gave birth on a birth seat compared to women who did not.

METHOD

An observational cohort study based on birth information collected prospectively. In total 10 629 live, singleton, non-instrumental births in cephalic presentation were studied.

RESULTS

Fewer women who gave birth on a birth seat experienced an overall intact genital tract compared to women who gave birth in any other position. Women who gave birth on a birth seat were less likely to have an episiotomy performed. Women who gave birth vaginally on a birth seat after a previous caesarean section may have an increased risk for sustaining a sphincter tear.

DISCUSSION

It is important to be aware of the decreased chance of an overall intact genital tract area when giving birth on a birth seat. Furthermore, there is a possibly increased risk of sphincter tear in women having a vaginal birth after caesarean. It is required and of importance to provide pregnant women with evidence-based information on factors associated with genital tract tears including birth positions.

Diabetes Mellitus and lower genital tract tears after vaginal birth: A cohort study

INTRODUCTION

Diabetes Mellitus in pregnancy is increasing. No existing studies have examined Diabetes Mellitus as the primary exposure for lower genital tract tears after vaginal birth. The objective was to study the association between Diabetes Mellitus (all types combined), Type 1 Diabetes Mellitus, Type 2 Diabetes Mellitus and Gestational Diabetes Mellitus and lower genital tract tears after vaginal birth.

MATERIAL AND METHODS

A register-based cohort study of women with singleton pregnancy and without a previous cesarean section at near-term (≥ 35 + 0 weeks) and term (≥ 37 + 0 weeks) gestational age, n = 31,297 at Aarhus University Hospital, Denmark from 1 January 2004 to 31 December 2012. The associations between Diabetes Mellitus and lower genital tract tears were analysed using a fixed multiple logistic regression analyses.

RESULTS

Approximately 32,000 women were eligible for the study; 796 women had diabetes (2.5%) and 1318 experienced anal sphincter injury (4.3%). The overall risk of lower genital tract tears was similar among women with a diagnosis of diabetes (Type1 Diabetes Mellitus, Type 2 Diabetes Mellitus, and Gestational Diabetes Mellitus) compared to women without diabetes, except for nulliparous women with Type1 Diabetes Mellitus who experienced a higher risk of episiotomies, crude and adjusted odds ratios (OR 2.13, 95% CI 1.14-3.97) and (OR 2.48, 95% CI 1.21-5.10), respectively.

CONCLUSIONS

Women with Diabetes Mellitus without a previous cesarean section who gave birth vaginally to a single child at term or near term did not experienced an increased risk of lower genital tract tears. However, nulliparous women with Type 1 Diabetes Mellitus experienced a higher risk of episiotomy. These results may be used to individualised counselling of women with Diabetes Mellitus regarding mode of birth and may reduce worries about genital tract tears in women with Diabetes Mellitus considering vaginal birth.

Single prior caesarean section and risk of anal sphincter injury

INTRODUCTION AND HYPOTHESIS

Injury to the anal sphincter at vaginal delivery remains the leading cause of faecal incontinence in women. Previous studies reported an increased incidence of obstetric anal sphincter injury (OASI) in women attempting vaginal birth after caesarean section (VBAC). The aim of the paper was to establish whether women in their second pregnancy, with one previous uterine scar, are at a higher risk of OASI compared with nulliparous women.

METHODS

All primiparous and secundiparous women with a previous caesarean section who delivered from 2008 to 2017 were analysed in a single-centre retrospective study. The primary endpoint was OASI. Labour characteristics in both groups were compared, and a multiple regression model was created.

RESULTS

There were 8573 vaginal deliveries of nulliparous women and 3453 deliveries of women in their second pregnancy with a previous caesarean section, of whom 550 had a successful VBAC. There was no significant difference in the rate of OASI between primiparous women and those who had a successful VBAC: 3.5% (297/8573) versus 3.1% (17/550), P = 0.730). Foetal macrosomia (>4 kg) and forceps delivery were risk factors for sphincter injury, while episiotomy and epidural anaesthesia were protective.

CONCLUSIONS

VBAC does not confer an increased risk of OASI after a first delivery by caesarean section when compared with nulliparous women. The rate of successful VBAC may be contributory and suggests that the risk conferred by VBAC may be unit-specific. Unit and national-level audit is necessary to investigate this risk further.

Perineal trauma with vaginal birth after a previous caesarean section: A retrospective cohort study

BACKGROUND

There is a paucity of information regarding perineal injuries in women who achieve vaginal birth after caesarean section (VBAC).

AIMS

To ascertain the rate of severe perineal injuries in women achieving VBAC at a major tertiary obstetric hospital, and to determine if vaginal birth is more likely to be associated with perineal injuries in women with one previous caesarean section compared with nulliparous women.

MATERIALS AND METHODS

A retrospective cohort study was undertaken of women with singleton pregnancies at term who delivered vaginally between 2013 and 2016. We compared nulliparous women with women who had undergone one previous caesarean section. The primary outcome analysed was the rate of third and fourth degree tears in each group. Secondary outcomes were major post-partum haemorrhage and instrumental delivery.

RESULTS

Totals of 10 663 nulliparous women and 629 VBAC women achieved vaginal birth. Of the VBAC women, 418 achieved their first vaginal birth (first VBAC group). Overall, there was no significant difference in the rate of third and fourth degree tears in the VBAC group compared with the nulliparous group (6.0% vs 5.6%; P = 0.73). There was no significant increase in anal sphincter injuries in the first VBAC group compared with the nulliparous group (6.0% vs 7.4%; P = 0.25).

CONCLUSION

No overall difference in the rate of severe perineal injuries between VBAC women and nulliparous women who achieve vaginal birth was observed in this study.

Episiotomy Technique and Management of Anal Sphincter Tears-A Survey of Clinical Practice and Education

OBJECTIVE

To ascertain current techniques of episiotomy used by obstetrics and gynaecology faculty members and residents in an academic department and to determine the current management strategies for third and fourth degree tears.

METHOD

A 14-question anonymous online survey was circulated to all faculty members and residents in the University of Toronto Department of Obstetrics and Gynaecology between October 2015 and March 2016. Results were analyzed descriptively or with Fisher exact test.

RESULTS

The survey response rate was 65.5% (169/258) among 108 faculty members and 61 residents. A history of clinical teaching regarding episiotomy was reported by 87% of faculty members and 75.4% of residents. Right mediolateral episiotomy was the most frequently used method among faculty members (88.0%) and residents (95.1%). The majority of respondents indicated that they would use an end-to-end technique for repair in the labour and delivery room under regional anaesthesia. Prophylactic antibiotics were never prescribed by 18.5% of faculty members and 13.1% of residents for third or fourth degree tears. In analysis by type of training, respondents who had taken a workshop or formal class were significantly more likely to prescribe physiotherapy postpartum (P = 0.001).

CONCLUSION

The most common reported method of learning episiotomy was clinical experience. A substantial number of responses differed from current SOGC guidelines for episiotomy technique and repair and management of anal sphincter injury. We propose developing a workshop and/or simulation-based method of instruction for episiotomy technique and repair.

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

INTRODUCTION

An awareness of risk factors for obstetric anal sphincter injuries (OASIS) is essential in order to reduce the occurrence of the primary event. These risk factors are demographic, obstetric and intrapartum related. We aimed to identify the risk factors for OASIS and to examine how modifiable risk factors may be used in order to reduce the incidence of OASIS.

METHODS

A retrospective, matched case-control study was conducted in the delivery ward of a single university teaching hospital in Israel, using data from January 2004 to July 2012. All singleton vaginal deliveries at term with OASIS were included. The controls included women matched at a ratio of 1:2 based on gestational age and deliveries that occurred immediately before and after the delivery of the women in the study group.

RESULTS

Overall, 113 OASIS were identified. Stepwise conditional logistic regression revealed that the first vaginal birth (OR = 7.6; 95% confidence interval (CI), 3.5-16.3; p < 0.001) particularly after a previous caesarean section (OR = 13.6; 95% CI, 4.7-39.3; p < 0.001) and the length of the second stage (OR 1.5; 95% CI, 1.1-2.1, p = 0.045) were the only risk factors for OASIS. Among 24 primiparous women who already had a prolonged second stage, 15 delivered by vacuum extraction and nine spontaneously; OASIS occurred in eight (53%) and three (33%) women, respectively. Multivariate analysis showed that this difference was not significant (OR = 2.3; 95% CI, 0.4-12.7; p = 0.35).

CONCLUSIONS

The first vaginal birth particularly after a caesarean delivery and the length of the second stage increased the risk of OASIS. Vacuum extraction performed to shorten a prolonged second stage is not necessarily protective.

Birth position and obstetric anal sphincter injury: a population-based study of 113 000 spontaneous births

BACKGROUND

The association between birth position and obstetric anal sphincter injury (OASIS) in spontaneous vaginal deliveries is unclear.

METHODS

The study was based on the Stockholm-Gotland Obstetric Database (Sweden) from Jan 1(st) 2008 to Oct 22(nd) 2014 and included 113 279 singleton spontaneous vaginal births with no episiotomy. We studied risk of OASIS with respect to the following birth positions: a) sitting, b) lithotomy, c) lateral, d) standing on knees, e) birth seat, f) supine, g) squatting, h) standing and i) all fours. All analyses were stratified for parity. General linear models were used to calculate risk ratios (RR) adjusted for maternal, pregnancy and fetal characteristics.

RESULTS

The rates of OASIS among nulliparous women, parous women and women undergoing vaginal birth after a caesarean (VBAC) were 5.7%, 1.3% and 10.6%, respectively. The rates varied by birth position: from 3.7 to 7.1% in nulliparous women, 0.6% to 2.6% in parous women and 5.6% to 18.2% in women undergoing VBAC. Regardless of parity, the lowest rates were found among women giving birth in standing position and the highest rates among women birthing in the lithotomy position. Compared with sitting position, the lithotomy position involved an increased risk of OASIS among nulliparous (adjusted RR 1.17, 95% CI 1.06-1.29) and parous women (adjusted RR 1.66, 95% CI 1.35-2.05). Birth seat and squatting position involved an increased risk of OASIS among parous women (adjusted RR [95% CI] 1.36 [1.03-1.80] and 2.16 [1.15-4.07], respectively). Independent risk factors for OASIS were maternal age, head circumference ≥35 cm, birth weight ≥4000 g, length of gestation ≥ 40 weeks, prolonged second stage of labour, non-occiput anterior presentation and oxytocin augmentation.

CONCLUSIONS

Compared with sitting position, lateral position has a slightly protective effect in nulliparous women whilst an increased risk is noted among women in the lithotomy position, irrespective of parity. Squatting and birth seat position involve an increase in risk among parous women.

Are there modifiable risk factors that may predict the occurrence of brachial plexus injury?

OBJECTIVE

To identify risk factors, particularly modifiable, associated with brachial plexus injury.

STUDY DESIGN

A retrospective case-control study conducted at a single hospital between the years 1993 and 2012. All neonates who were diagnosed of brachial plexus injury were included. A control group matched at a ratio of 1:2 was randomly selected. Demographic and obstetric data were obtained from the hospital discharge register with ICD-9 codes and crosschecked with the labor medical records. All medical files were manually checked and validated. A stepwise logistic regression model was performed to identify independent predictors for brachial plexus injury before delivery among those found significant in the univariate analysis.

RESULTS

Of all 83 806 deliveries that took place during this period, 144 cases of brachial plexus injury were identified (1.7/1000 deliveries). Overall, 142 cases and 286 controls had available data. Among the study group, 41 (28.9%) had documented shoulder dystocia compared with 1 (0.4%) among the controls (P<0.0001). Logistic regression analysis revealed that maternal age above 35 years (P=0.01; odds ratio (OR) 2.7; 95% confidence interval (CI) 1.3 to 5.7), estimated fetal weight before delivery (P<0.0001; OR 2.5; 95% CI 1.7 to 3.8, for each 500 g increase), vaginal birth after cesarean (P=0.02; OR 3.3; 95% CI 1.2 to 8.8) and vacuum extraction (P=0.02; OR 3.6; 95% CI 1.2 to 10.3) were all found to be independent predictors for developing brachial plexus injury. When stratifying the analysis according to parity, vacuum delivery was found to be an independent risk factor only among primiparous women (OR 6.0; 95% CI 1.7 to 21.6).

CONCLUSIONS

The findings suggest that very few factors contributing to brachial plexus injury are modifiable. For that reason, it remains an unpredictable and probably an unavoidable event.