Trends in obstetric anal sphincter injuries and associated risk factors for vaginal singleton term births in New South Wales 2001-2009

Prediction models for perineal lacerations during childbirth: A systematic review and critical appraisal

BACKGROUND

Perineal lacerations could lead to substantial morbidities for women. A reliable prediction model for perineal lacerations has the potential to guide the prevention. Although several prediction models have been developed to estimate the risk of perineal lacerations, especially third- and fourth-degree perineal lacerations, the evidence about the model quality and clinical applicability is scarce.

OBJECTIVES

To systematically review and critically appraise the existing prediction models for perineal lacerations.

METHODS

Seven databases (PubMed, Embase, The Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, SinoMed, China National Knowledge Infrastructure, and Wanfang Data) were systematically searched from inception to July 2022. Studies that developed prediction models for perineal lacerations or performed external validation of existing models were considered eligible to include in the systematic review. Two reviewers independently conducted data extraction according to the Checklist for critical Appraisal and data extraction for systematic Reviews of prediction Modelling Studies. The risk of bias and the applicability of the included models were assessed with the Prediction Model Risk of Bias Assessment Tool. A narrative synthesis was performed to summarize the characteristics, risk of bias, and performance of existing models.

RESULTS

Of 4345 retrieved studies, 14 studies with 22 prediction models for perineal lacerations were included. The included models mainly aimed to estimate the risk of third- and fourth-degree perineal lacerations. The top five predictors used were operative vaginal birth (72.7 %), parity/previous vaginal birth (63.6 %), race/ethnicity (59.1 %), maternal age (50.0 %), and episiotomy (40.1 %). Internal and external validation was performed in 12 (54.5 %) and seven (31.8 %) models, respectively. 13 studies (92.9 %) assessed model discrimination, with the c-index ranging from 0.636 to 0.830. Seven studies (50.0 %) evaluated the model calibration using the Hosmer-Lemeshow test, Brier score, or calibration curve. The results indicated that most of the models had fairly good calibration. All the included models were at higher risk of bias mainly due to unclear or inappropriate methods for handling missing data and continuous predictors, external validation, and model performance evaluation. Six models (27.3 %) showed low concerns about applicability.

CONCLUSIONS

The existing models for perineal lacerations were poorly validated and evaluated, among which only two have the potential for clinical use: one for women undergoing vaginal birth after cesarean delivery, and the other one for all women undergoing vaginal birth. Future studies should focus on robust external validation of existing models and the development of novel models for second-degree perineal laceration.

PROSPERO REGISTRATION NUMBER

CRD42022349786.

TWEETABLE ABSTRACT

The existing models for perineal lacerations during childbirth need external validation and updating. Tools are needed for second-degree perineal laceration.

Management of Third and Fourth-Degree Perineal Tears After Vaginal Birth. Guideline of the DGGG, OEGGG and SGGG (S2k-Level, AWMF Registry No. 015/079, December 2020)

Purpose This guideline provides recommendations for the diagnosis, treatment and follow-up care of 3rd and 4th degree perineal tears which occur during vaginal birth. The aim is to improve the management of 3rd and 4th degree perineal tears and reduce the immediate and long-term damage. The guideline is intended for midwives, obstetricians and physicians involved in caring for high-grade perineal tears.

Methods A selective search of the literature was carried out. Consensus about the recommendations and statements was achieved as part of a structured process during a consensus conference with neutral moderation.

Recommendations After every vaginal birth, a careful inspection and/or palpation by the obstetrician and/or the midwife must be carried out to exclude a 3rd or 4th degree perineal tear. Vaginal and anorectal palpation is essential to assess the extent of birth trauma. The surgical team must also include a specialist physician with the appropriate expertise (preferably an obstetrician or a gynecologist or a specialist for coloproctology) who must be on call. In exceptional cases, treatment may also be delayed for up to 12 hours postpartum to ensure that a specialist is available to treat the individual layers affected by trauma. As neither the end-to-end technique nor the overlapping technique have been found to offer better results for the management of tears of the external anal sphincter, the surgeon must use the method with which he/she is most familiar. Creation of a bowel stoma during primary management of a perineal tear is not indicated. Daily cleaning of the area under running water is recommended, particularly after bowel movements. Cleaning may be carried out either by rinsing or alternate cold and warm water douches. Therapy should also include the postoperative use of laxatives over a period of at least 2 weeks. The patient must be informed about the impact of the injury on subsequent births as well as the possibility of anal incontinence.

Risk factors for obstetric anal sphincter injury recurrence: A systematic review and meta-analysis

BACKGROUND

Women with previous obstetric anal sphincter injuries (OASIs) are at a higher risk of recurrence in the subsequent pregnancy, which may lead to the development or worsening of anal incontinence. Due to a lack of evidence, few recommendations can be made about the factors that may affect the risk of OASI recurrence.

OBJECTIVE

We sought to conduct a systematic review and meta-analysis to investigate potential risk factors for recurrent OASIs.

SEARCH STRATEGY

Studies up to May 2019 were identified from PubMed, Scopus, Cochrane Library, and ISI Web of Science.

SELECTION CRITERIA

Studies assessing the impact of risk factors on OASI recurrence in subsequent pregnancies were included. Reviews, letters to the editor, conference abstracts, book chapters, guidelines, Cochrane reviews, and expert opinions were excluded.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent reviewers. Odds ratio and standardized mean difference were chosen as effect measures. Pooled estimates were calculated using the random-effects model.

MAIN RESULTS

The meta-analysis showed that maternal age, gestational age, occiput posterior presentation, oxytocin augmentation, operative delivery, and shoulder dystocia were associated with the risk of recurrent OASIs in the subsequent delivery.

CONCLUSION

Prenatal and intrapartum risk factors are associated with recurrence of OASI. PROSPERO registration no. CRD42020178125.

Mediolateral/lateral episiotomy with operative vaginal delivery and the risk reduction of obstetric anal sphincter injury (OASI): A systematic review and meta-analysis

Introduction and hypothesis

OASI complicates approximately 6% of vaginal deliveries. This risk is increased with operative vaginal deliveries (OVDs), particularly forceps. However, there is conflicting evidence supporting the use of mediolateral/lateral episiotomy (MLE/LE) with OVD. The aim of this study was to assess whether MLE/LE affects the incidence of OASI in OVD.

Methods

Electronic searches were performed in OVID Medline, Embase and the Cochrane Library. Randomised and non-randomised observational studies investigating the risk of OASI in OVD with/without MLE/LE were eligible for inclusion. Pooled odds ratios (OR) were calculated using Revman 5.3. Risk of bias of was assessed using the Cochrane RoB2 and ROBINS-I tool. The quality of evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

Results

A total of 703,977 patients from 31 studies were pooled for meta-analysis. MLE/LE significantly reduced the rate of OASI in OVD (OR 0.60 [95% CI 0.42–0.84]). On sub-group analysis, MLE/LE significantly reduced the rate in nulliparous ventouse (OR 0.51 [95% CI 0.42–0.84]) and forceps deliveries (OR 0.32 [95% CI 0.29–0.61]). In multiparous women, although the incidence of OASI was lower when a ventouse or forceps delivery was performed with an MLE/LE, this was not statistically significant. Heterogeneity remained significant across all studies (I² > 50). The quality of all evidence was downgraded to “very low” because of the critical risk of bias across many studies.

Conclusions

MLE/LE may reduce the incidence of OASI in OVDs, particularly in nulliparous ventouse or forceps deliveries. This information will be useful in aiding clinical decision-making and counselling in the antenatal period and during labour.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00192-022-05145-1.

Modifiable and non-modifiable risk factors for obstetric anal sphincter injury in a Norwegian Region: a case-control study

Background

Obstetric anal sphincter injury (OASI) is a common and severe complication of vaginal delivery and may have short- and long-term consequences, including anal incontinence, sexual dysfunction and reduced quality of life. The rate of OASI varies substantially between studies and national birth statistics, and a recent meta-analysis concluded that there is a need to identify unrecognized risk factors. Our aim was therefore to explore both potential modifiable and non-modifiable risk factors for OASI.

Methods

We performed a case–control study in a single center maternity clinic in South-Eastern Norway. Data were extracted retrospectively from an institutional birth registry. The main outcome measure was the occurrence of the woman’s first-time 3^rd or 4^th degree perineal lesion (OASI) following singleton vaginal birth after 30 weeks’ gestation. For each woman with OASI the first subsequent vaginal singleton delivery matched for parity was elected as control. The study population included 421 women with OASI and 421 matched controls who gave birth during 1990–2002. Potential risk factors for OASI were assessed by conditional logistic regression analyses.

Results

The mean incidence of OASI was 3.4% of vaginal deliveries, but it increased from 1.9% to 5.8% during the study period. In the final multivariate regression model, higher maternal age and birthweight for primiparous women, and higher birthweight for the multiparous women, were the only non-modifiable variables associated with OASI. Amniotomy was the strongest modifiable risk factor for OASI in both primi- (odds ratio [OR] 4.84; 95% confidence interval [CI] 2.60–9.02) and multiparous (OR 3.76; 95% CI 1.45–9.76) women, followed by augmentation with oxytocin (primiparous: OR 1.63; 95% CI 1.08–2.46, multiparous: OR 3.70; 95% CI 1.79–7.67). Vacuum extraction and forceps delivery were only significant risk factors in primiparous women (vacuum: OR 1.91; 95% CI 1.03–3.57, forceps: OR 2.37; 95% CI 1.14–4.92), and episiotomy in multiparous women (OR 2.64; 95% CI 1.36–5.14).

Conclusions

Amniotomy may be an unrecognized independent modifiable risk factor for OASI and should be further investigated for its potential role in preventive strategies.

Mediolateral episiotomy and risk of obstetric anal sphincter injuries and adverse neonatal outcomes during operative vaginal delivery in nulliparous women: a propensity-score analysis

Background

The potential protective effect of mediolateral episiotomy for obstetrical anal sphincter injuries (OASIs) remains controversial during operative vaginal delivery because of the difficulties to take into account the risk factors and clinical conditions at delivery; in addition, little is known about the potential benefits of mediolateral episiotomy on neonatal outcomes.

The objectives were to investigate the associations between mediolateral episiotomy and both OASIs and neonatal outcomes, using propensity scores.

Methods

We performed a retrospective population-based observational study from a perinatal registry that includes all births in a French region between 2010 and 2017. All nulliparous women with singleton pregnancy delivering by operative vaginal deliveries at 37 weeks gestational age or later were included. Inverse-probability-of-treatment weighting with propensity scores was used to minimize indication bias. OASIs was defined as third and fourth-degree tears according to Royal College of Obstetricians and Gynecologists. Two neonatal outcomes were studied: condition at birth (5-min Apgar score less than 7 and/or umbilical artery pH less than 7.10), and admission to neonatal intensive care unit.

Results

The study population consisted of 7589 women; 2880 (38.0%) received mediolateral episiotomy. After applying propensity scores, episiotomy was associated with a lower rate of OASIs in forceps/spatula delivery (2.3 vs 6.8%, Risk Ratio (RR) 0.38, 95% Confidence Interval (CI) 0.28–0.52) and in vacuum delivery (1.3 vs 3.4%, RR 0.27, 95% CI 0.20–0.38) as compared with no episiotomy. Mediolateral episiotomy was associated with better condition at birth in case of forceps/spatula delivery (4.5 vs 8.8%, RR 0.56, 95% CI 0.39–0.81). In cases of fetal distress (40.7%), mediolateral episiotomy was associated with better condition of infant at birth in women who delivered by forceps/spatula (4.2 vs 13.5%, RR 0.52, 95% CI 0.31–0.89). No association was found with neonatal unit admission (RR 0.93, 95% CI 0.50–1.74).

Conclusions

Use of mediolateral episiotomy was associated with a lower rate of OASIs during operative vaginal delivery, and in infants it was associated with better condition at birth following forceps/spatula delivery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04396-6.

Association between second stage of labour length and risk of obstetrical anal sphincter injury in nulliparous women: a population-based retrospective cohort study

INTRODUCTION AND HYPOTHESIS

Obstetrical anal sphincter injury (OASIS) is a common consequence of vaginal delivery in nulliparas and carries the risk of short- and long-term morbidity. The objective of this study was to estimate the association between the duration of the second stage of labour and OASIS risk.

METHODS

A population-based, retrospective cohort of nulliparas delivering singleton, vertex, non-anomalous fetuses at term in Nova Scotia, Canada, from 2005 to 2019, were identified using the Nova Scotia Atlee Perinatal Database. Poisson regression models were used to estimate risk ratios (RR) with robust 95% confidence intervals (CI) adjusting for confounding variables to investigate the association between the length of the second stage and OASIS in the entire cohort and in operative vaginal deliveries.

RESULTS

Of 36,662 participants, 7.6% sustained an OASIS (6.8% third-degree, 0.8% fourth-degree tear). The proportion of participants who sustained an OASIS increased over the study period. For each 30-min increase in the length of second stage, the OASIS risk increased by 11% (RR 1.11, 95% CI 1.10-1.12). When stratified by mode of delivery, second stage length ≥ 90 min was associated with an increased OASIS risk in spontaneous (RR 1.35, 95% CI 1.15-1.58) and vacuum-assisted vaginal deliveries (RR 1.42, 95% CI 1.11-1.81). In forceps-assisted vaginal deliveries, OASIS risk was increased, with shorter and longer durations of the second stage.

CONCLUSION

Increasing length of the second stage of labour was associated with increasing risk of OASIS overall, but the association was heterogeneous between modes of delivery. Length of the second stage should be considered in counseling about OASIS risk.

Identifying the factors that influence midwives' perineal practice at the time of birth in the United Kingdom

OBJECTIVE

The Obstetric Anal Sphincter Injuries (OASI) Care Bundle is designed to reduce the incidence of obstetric anal sphincter injuries. However, introducing behavioural change requires an understanding of current practice. This study aims to establish midwives practise at the time of birth, and the factors that influence this.

DESIGN

Quantitative research - a national online survey.

SETTING

Nationwide - United Kingdom (UK). Participants 563 midwives from across the UK.

METHODS

An online survey of midwives' practice. Midwives were invited to participate through the Supervisor of Midwives network. Consent was sought on the landing page. Data analysis using descriptive and inferential statistics, with sub group analyses were used to explore variations in practice. Measurements Number of midwives using "hands on" the perineum and the influences on midwives' perineal practice at the time of birth.

FINDINGS

Most midwives preferred to use "hands on" the perineum at the time of birth (61.4%). "Hands on" practise was significantly associated with where midwives worked (p<0.001), risk factors for OASI (p<0.001), and the approach that they were taught in their midwifery training (p<0.01). Midwives expressed lack of confidence in some areas with a third unsure that they could identify the third degree tear category b (38.2%) or c (34.3%).

KEY CONCLUSIONS

There has been a growth in the number of midwives using "hands on" at the time of birth but midwives feel that they require additional training in regards to identifying an OASI. The study should be repeated following the roll out of the OASI care bundle, to identify its impact on midwives' perineal practice.

IMPLICATIONS FOR PRACTICE

The study identified that there needs to be an improvement in the recognition of OASI by midwives, and in future repeating the study would identify whether the OASI care bundle has influenced midwives' practice.

How a perineal care bundle impacts midwifery practice in Australian maternity hospitals: A critical, reflexive thematic analysis

BACKGROUND

A care bundle to reduce severe perineal trauma (the bundle) was introduced in 28 Australian maternity hospitals in 2018. The bundle includes five components of which only one - warm perineal compresses - has highest level evidence. There is scant published research about the impact of implementation of perineal bundles.

QUESTION

How does a perineal care bundle impact midwifery practice in Australian maternity hospitals?

METHODS

Purposively sampled midwives who worked in hospitals where the bundle had been implemented. Interested midwives were recruited to participate in one-to-one, semi-structured interviews. The researchers conducted critical, reflexive thematic analysis informed by Foucauldian concepts of power.

FINDINGS

We interviewed 12 midwives from five hospitals in one state of Australia. Participants varied by age, clinical role, experience, and education. Three themes were generated: 1) bundle design and implementation 2) changing midwifery practice: obedience, subversion, and compliance; and 3) obstetric dominance and midwifery submission.

DISCUSSION

The bundle exemplifies tensions between obstetric and midwifery constructs of safety in normal birth. Participants' responses appear consistent with oppressed group behaviour previously reported in nurses and midwives. Women expect midwives to facilitate maternal autonomy yet decision-making in maternity care is commonly geared towards obtaining consent. In our study midwives encouraged women to consent or decline depending on their personal preferences.

CONCLUSION

The introduction of the perineal bundle acts as an exemplar of obstetric dominance in Australian maternity care. We recommend midwives advocate autonomy - women's and their own - by using clinical judgement, evidence, and woman-centred care.

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

AIM

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

METHOD

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

RESULTS

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

CONCLUSION

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

Management of obstetric anal sphincter injury: Colorectal surgeons' perspectives in Australia and New Zealand

BACKGROUND

Obstetric anal sphincter injuries (OASIs) are a significant complication of vaginal delivery, and a leading cause of anal incontinence in women.

AIMS

The aims were to explore the management of OASIs in Australia and New Zealand (ANZ) by colorectal surgeons and how this compares with current recommendations and international experience, and to identify the deterrents to the provision of best-practice care among colorectal surgeons.

MATERIALS AND METHODS

Three hundred colorectal surgeons of the Colorectal Surgical Society of ANZ were mailed questionnaires. Areas of interest included: surgeon demographics; exposure to OASIs; understanding of current recommendations; and opinions regarding the importance of symptoms and assessment tools in OASIs.

RESULTS

There were 94 completed questionnaires (response rate 31.3%). Fifty-seven surgeons (60.6%) reported low exposure to OASIs during their fellowship training. Greater than 90% believed patients with grade three tears and above should have anal sphincter assessment. Sixty-six (70.2%) reported that they routinely review women who have had OASIs. However, 56.4% were unaware if their obstetrics department followed a standard protocol for OASIs. Surgeons practising in metropolitan centres reported higher rates of their obstetrics department following a protocol (P = 0.013), and greater access to investigative tools (P < 0.001), when compared to rural-based surgeons.

CONCLUSIONS

Most ANZ colorectal surgeons have had minimal training in OASI management. Colorectal surgeons are more commonly involved with OASI patients in the non-acute setting. Management protocols involving a multidisciplinary team of both colorectal surgeons and obstetricians should be clearly defined, and the gap between metropolitan and rural centres needs to be reviewed.

Evaluation of a policy of restrictive episiotomy on the incidence of perineal tears among women with spontaneous vaginal delivery: A ten-year retrospective study

INTRODUCTION

Routine episiotomy is no longer recommended to limit obstetrical anal sphincter injuries (OASIs). We aimed to evaluate the effect of a restrictive policy of episiotomy on the risk of OASIs during spontaneous vaginal deliveries.

MATERIAL AND METHODS

We performed a retrospective single-center observational study among women with a term singleton cephalic fetus, with spontaneous vaginal delivery. The occurrence of episiotomy, intact perineum, first, second, third or fourth-degree (OASIs) perineal tears were compared before (period A, from 01/01/2006 to 12/31/2008) and after (period B, from 01/01/2012 to 12/31/2016) implementation of the restrictive policy. Odds of perineal tear were estimated using multivariable logistic regression models, stratified by parity.

RESULTS

From 2006-2016, the rate of episiotomy decreased, from 14.9 % (n/N=200/1141) to 4.7 % (94/1912). In period B (N=8984) vs A (N=8984), the rates of episiotomy were, 12.9 vs 26.6 % for nulliparas (p<0.01) and 2.3 vs 6.8 % for multiparas (p<0.01). Odds of OASIs were not different in period B vs A, both for nulliparas (0.9 vs 0.8 %, AOR=0.88(0.38-2.05)) and multiparas (0.4 vs 0.2 %, AOR=2.28(0.63-8.29). Odds of second-degree tear were higher in period B vs A, both for nulliparas (39.8 vs 17.4 %, AOR=2.55(2.11-3.08) and multiparas (26.2 vs 12.8 %, AOR=2.26(1.95-2.66)); and odds of intact perineum were lower (for nulliparas, 15.8 vs 24.9 %, AOR=0.61(0.42-0.90) and for multiparas, 47.1 vs 56.0 %, AOR=0.61(0.49-0.76)). No difference was observed for first-degree tears.

CONCLUSION

The progressive implementation of a restrictive policy of episiotomy during spontaneous vaginal delivery was not associated with an increased risk of OASIs over a ten-year period.

Selective use of episiotomy: what is the impact on perineal trauma? Results from a retrospective cohort study

PURPOSE

To evaluate the effects of selective use of episiotomy on perineal trauma.

METHODS

We performed a retrospective cohort study on consecutive vaginal deliveries from January 2010 to December 2016. From January 2010 to December 2011 episiotomy was performed liberally, based only on individual midwife/doctor's decision. Since January 2012, a shared selective use of episiotomy policy has been introduced. To evaluate the range of perineal trauma in spontaneous second-degree perineal tears, a sub-classification of second-degree lacerations has been introduced dividing them into two sub-groups: A (smaller than the average episiotomy) and B (spontaneous vaginal tear larger than the average episiotomy). The primary outcomes were the incidence and type of perineal trauma, with the proportion of type A and type B second-degree spontaneous tears under a policy of selective episiotomy.

RESULTS

Deliveries not exposed to selective use of episiotomy were 1583 (Group 1), those exposed to selective use of episiotomy were 6409 (Group 2). In Group 2 episiotomy rate decreased, and incidence of intact perineum, first- and second-degree lacerations increased. The incidence of third- and fourth-degree lacerations did not change. Spontaneous second-degree lacerations occurred in 19.4% and 36.8% of women in group 1 and 2, respectively. With a selective episiotomy policy, 88.3% of second-degree tears was classified as type A.

CONCLUSIONS

The selective use of episiotomy is clinically feasible and effective. This policy seems to be associated with a lower delivery-related perineal trauma as showed by the sub-classification, that could be a useful tool to monitor obstetric care.

The impact of maternal body mass index on the rate of obstetric anal sphincter injury in nulliparous women: A Victorian retrospective cohort study

BACKGROUND

Maternal obesity is an important comorbidity in contemporary obstetrics practice and is associated with significantly increased perinatal complications. Obstetric anal sphincter injury (OASIS) sustained during labour can lead to faecal incontinence, chronic pain and effects on quality of life. Currently, it is unclear if maternal body mass index (BMI) influences the risk of sustaining OASIS.

AIM

To investigate the impact of increased BMI on the rate of OASIS among nulliparous women.

MATERIALS AND METHODS

A retrospective cohort study was conducted, which included nulliparous women with singleton, vaginal deliveries ≥37 weeks gestation at a Victorian regional centre between 2007 and 2017 (n = 3335). Logistic regression was performed to calculate unadjusted and adjusted odds ratios (aOR). Women were grouped by World Health Organization BMI categories, and the rates of OASIS were evaluated.

RESULTS

Women with a BMI ≥ 25 were significantly less likely to develop OASIS compared to women with a BMI < 25 (aOR 0.60, 95% CI 0.41-0.89). Women with a BMI ≥ 35 had significantly decreased odds of OASIS compared to normal weight women (aOR 0.27, 0.10-0.78). While not statistically significant, the odds of OASIS decreased with each increase in BMI class. Other statistically significant risk factors were maternal age, birth weight, forceps delivery, non-smokers (aOR 4.03, 1.46-11.1) and diabetes mellitus (aOR 9.48, 2.1-41.4).

CONCLUSION

Women with a BMI ≥ 25 were less likely to sustain OASIS compared to women with a BMI < 25. Furthermore, the odds of OASIS decreased for each increase in BMI category. These findings warrant further investigation into the mechanism of this protective effect.

What is the total impact of an obstetric anal sphincter injury? An Australian retrospective study

Introduction

Most data on obstetric anal sphincter injury (OASI) reflect short-term (< 12 months) or much longer term (> 10 years) impact. This study aimed to collate the extent of medium-term symptomology (1–6 years) and observe the effect on future birth choices to evaluate the cumulative impact of OASI in affected women.

Methods

A retrospective cohort of women affected by OASI completed a questionnaire covering bowel symptomology, sexual function, life impact and future birth choices. A custom-created adverse composite outcome for OASI incorporating effects on daily life, flatal/fecal incontinence and sexual function (OASIACO) was used as a threshold score to identify women with high levels of symptoms.

Results

Of 265 eligible and contactable women, 210 questionnaires were received (response rate 79%) at a mean of 4 years post-OASI. More than half (54%) experienced an OASIACO. A forceps birth (p = 0.03) or more severe grade of tear (p = 0.03) was predictive of OASIACO. One hundred one women had further children, with 48% reporting their delivery choices were impacted, 32% electing a cesarean delivery and 26% shifting to private care. Eighty women (40%) had not given birth again, and 29 (36%) of these indicated their OASI influenced this decision.

Conclusions

The total impact of an OASI on women affected is substantial. More than half experience ongoing symptoms and close to half report an impact on their future birth choices. It follows there would be a consequential load on the healthcare sector, and improved management and prevention programs should be implemented.

Electronic supplementary material

The online version of this article (10.1007/s00192-019-04108-3) contains supplementary material, which is available to authorized users.

Incidence and risk factors for obstetric anal sphincter ruptures, OASIS, following the introduction of preventive interventions. A retrospective cohort study from a Norwegian hospital 2012-2017

OBJECTIVE

A decrease of obstetric anal sphincter injuries (OASIS) was observed after preventive interventions were implemented at a Norwegian university hospital. The aim was to investigate whether the improvement had sustained over the following years.

MATERIALS AND METHODS

We performed a retrospective cohort study of 18 258 singleton vaginal cephalic births, ≥37 + 0 weeks of gestation during 2012-2017, examining data from the hospital's birth journals and separate registration forms. Interventions to prevent OASIS were implemented in 2011, and training in practical skills was repeated each year.

MAIN OUTCOME MEASURES

The main outcome was OASIS (n = 377).

RESULTS

Frequency of OASIS overall decreased from 3.6% prior to 2011 to 2.1% after the intervention and sustained at that level throughout the study period. A trend of fewer OASIS among spontaneous deliveries, decreasing from 2.1% to 1.2% (p = 0.01) was observed, but no trend was seen for instrumental deliveries (p = 0.37), where the incidence fluctuated between 4.0% and 9.3% with an average of 6.5%. Primiparity, increased maternal age and increased fetal head circumference were associated with more OASIS in spontaneous deliveries. In instrumental deliveries, primiparity, occiput posterior position and increased fetal head circumference were associated with more OASIS, whilst episiotomy was associated with fewer OASIS.

CONCLUSION

The incidence of obstetric anal sphincter injuries maintained at a similar level of around 2.1% during the six following years after introducing preventive interventions. Regularly repetition and practical training seemed to be effective.

Risk factors for perineal trauma in the primiparous population during non-operative vaginal delivery

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injuries (OASIS) are more common in the primiparous population, especially during operative vaginal delivery (OVD). It would therefore be interesting to establish what factors influence the risk of OASIS when adjusting for the risk bias of OVD.

METHODS

Retrospective analysis of prospectively collected data from the maternity database at University of Southampton NHS Foundation Trust of primiparous women sustaining OASIS during a singleton, term, cephalic, non-operative vaginal delivery between 2004 and 2015. A control comparison was made of women with otherwise identical birthing conditions but resulting with intact perinea, delivering between 2014 and 2015. Univariate and multivariate logistic regression compared maternal, intrapartum and neonatal factors of those sustaining OASIS with those with an intact perineum.

RESULTS

Seven hundred fifty-six women sustaining an OASI met the criteria, and comparisons were made with a control population of 212. Those sustaining an OASI were significantly older (p < 0.001), more likely to be Asian (4.6-fold, p < 0.001) and had heavier babies, with a 3.6-fold greater proportion over 4 kg (p = 0.001). They were more likely to have delivered post-term and had longer second stages of labour (both p < 0.001). Epidural anaesthesia was associated with a 67% reduction in OASIS.

CONCLUSIONS

These findings support previous research regarding risk factors for OASIS. By controlling for bias of risk associated with operative vaginal delivery, this revealed a potential protective effect of the use of regional anaesthesia.

The impact of third- or fourth-degree perineal tears on the second pregnancy: A cohort study of 182,445 Scottish women

This study aimed to investigate the reproductive impact of a third- or fourth-degree tear in primigravid women. A retrospective population-based cohort study was conducted using data from Scottish Morbidity Records (SMR02). Primigravid women with a vaginal birth in Scotland from 1997 until 2010 were included. Exposure was third- or fourth-degree tear in the first pregnancy. The second pregnancy rate, interpregnancy interval and third- or fourth-degree tear in a second pregnancy were the primary outcomes. A nested case-control study was used to determine factors associated with repeat third- or fourth-degree tears in a second vaginal birth. Cox regression analysis and logistic regression were used to look for associations. Initial third- or fourth-degree tear occurred in 2.8% women (5174/182445). The percentage of third- or fourth-degree tears in first vaginal births increased from 1% in 1997 to 4.9% in 2010. There was no difference in having a second pregnancy (adjusted Odds Ratio (aOR) 0.98 (99%CI 0.89–1.09)) or the median interpregnancy interval to second pregnancy (adjusted Hazard Ratio (aHR) 1.01 (99%CI 0.95–1.08)) after an initial third- or fourth-degree tear. Women were over four times more likely to have a repeat injury in a subsequent vaginal birth (n = 149/333, aOR 4.68 (99% 3.52–6.23)) and were significantly more likely to have an elective caesarean section in their second pregnancy (n = 887/3333, 26.6%; 12.75 (11.29–14.40)). Increased maternal age and birthweight ≥4500g were risk factors for repeat injury. Third- and fourth-degree tears are increasing in Scotland. Women do not delay or avoid childbirth after initial third- or fourth-degree tear. However, women are more likely to have a repeat third- or fourth-degree tear or an elective caesarean section in the second pregnancy. Strategies to prevent third- or fourth-degree tears are needed.

Obstetrical and epidemiological factors influence the severity of anal incontinence after obstetric anal sphincter injury

BACKGROUND

Obstetric anal sphincter injury (OASI) is one of the most severe obstetrical complications. Although risk factors for OASI have been identified, little is known about various parameters that can influence symptoms' severity. The aim of this study is to explore whether obstetrical and epidemiological factors can have an effect on the severity of symptoms after OASI.

METHODS

11.483 deliveries between January 2010 and December 2014 were reviewed, and data from 88 women with OASI are presented.

RESULTS

The only statistically significant differences between symptomatic and asymptomatic women were age (p = 0.02), body mass index (p = 0.04) and the use of forceps (p = 0.04). Women with more severe symptoms were more likely to have received oxytocin during the second stage of labor (p = 0.03) and had shorter delivery to follow-up interval (p = 0.008).

CONCLUSIONS

Modifiable factors such as use of forceps and oxytocin should be taken into consideration in clinical practice.

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.

Enhancing recognition of obstetric anal sphincter injuries in six maternity units in Palestine: an interventional quality improvement study

OBJECTIVE

To explore the impact of a training intervention on obstetric anal sphincter injuries' (OASIS) detection rate.

DESIGN

Prospective quality improvement interventional study.

SETTING

Six secondary and tertiary maternity units in Palestine.

POPULATION

Women having singleton vaginal births ≥23 weeks' gestation or babies weighing ≥500 g (n=22 922). Caesarean births (n=5431), multiple gestations (n=443) and vaginal births of unregistered perineum status (n=800) were excluded.

INTERVENTIONS

Training programme for enhancing OASIS detection was conducted between 31 January and 31 December 2015. International experts delivered 2-day standardisation workshop teaching OASIS diagnosis and repair to each maternity unit. They also provided additional training to three research fellows employed in three of the maternity units. This was followed by 13-week period of data collection (phase 1). Research fellows then delivered training intervention over 15-week interval (phase 2), including theoretical teaching and 'onsite' training in perineal trauma assessment within the six maternity units. Finally, 13-week postintervention observation (phase 3) followed.

PRIMARY OUTCOME MEASURE

OASIS rates were used as surrogate for OASIS recognition. OASIS rates were compared between different phases and between the two maternity unit groups (research fellow and non-research fellow based) using Pearson's χ² test.

RESULTS

A total 22 922 women were included. Among primiparous women, OASIS rate was higher in phase 2 (2.8%, p<0.001) and phase 3 (3.1%, p<0.001) than phase 1 (0.5%). However, no significant differences were detected in the rates of severe OASIS (third-degree 3c and fourth-degree tears) between phase 1 and 2 (0.5% vs 0.3%), because this would have required at least 103 women with severe OASIS to be included in each phase. Among parous women, OASIS rate was significantly higher in phase 2 (0.6%, p=0.002) but not in phase 3 (0.4%, p=0.071) compared with phase 1 (0.2%). Research fellows' maternity units showed higher OASIS rates among primiparous women in phase 2 (3.6% vs 1.4%, p=0.001) and phase 3 (4.3% vs 0.8%, p<0.001) than non-research fellows' maternity units.

CONCLUSIONS

This work is basically an epidemiological study which has identified the prevalence of perineal lacerations and their severity on a large sample of women representative of an entire geographical ethnic region. The quality improvement intervention improved OASIS detection mainly in the research fellows' maternity units. Regular mandatory national programmes in obstetric perineal trauma assessment and management by local champions are essential to mitigate the risk of missing significant degrees of trauma.

Perineal length among Vietnamese women

OBJECTIVE

Vietnamese clinicians routinely perform episiotomies in the belief that 3rd-4th degree tears may be prevented, based partly on the view that Vietnamese women have a short perineal length that puts them at increased risk of tears. However, there is no evidence to suggest Vietnamese women have a short perineum compared with other populations. We aimed to determine the mean perineal length among Vietnamese women in early labor and in the second stage, and to compare this to findings from similar studies in other populations.

MATERIALS AND METHODS

We undertook an observational study in a tertiary obstetric hospital in Vietnam from October 2014 to June 2015. Pregnant women who presented in early labor with a live singleton cephalic presentation at ≥37 weeks gestation were eligible. Perineal length was measured early in the 1st stage of labor (≤4 cm dilation) and in 2nd stage of labor (10 cm dilation). Mean perineal length was compared to other populations using t-tests.

RESULTS

Of 395 women, 159 (40.3%) were nulliparous and 236 (59.8%) multiparous. Overall the mean perineal length in early labor was 3.4 cm (±0.4), and did not differ by parity. Mean perineal length among Vietnamese women was significantly shorter (P < 0.001) than other populations (means 3.8-4.6 cm). Among 365 women who reached 2nd stage the mean perineal length was 4.3 cm (±0.6).

CONCLUSION

The perception that Vietnamese women have a relatively shorter perineal length appears to have some basis and outcomes reported from episiotomy trials may not be generalizable to Vietnamese women.

Factors associated with obstetric anal sphincter injuries in midwife-led birth: A cross sectional study

INTRODUCTION

Obstetric anal sphincter injurie (OASI) in vaginal births are a serious complication, and are associated with maternal morbidity. Focus on modifiable factors in midwives clinical skills and competences contributing to prevent the occurrence of OASI are essential. The objective of this study was to investigate the association between OASI and factors related to midwife-led birth such as manual support of perineum, active delivery of baby's shoulders, maternal birth position, and pushing and breathing techniques in second stage of labour.

METHODS

A prospective cross sectional study including primiparous (n = 129) and multiparous (n = 628) women in midwife-led non-instrumental deliveries with OASI (n = 96) or intact perineum (n = 661). Data were collected in a university hospital in Norway with two different birth settings: an alongside midwife-led unit with approximately 1500 births per year and an obstetrical unit with approximately 3500 births per year. In midwife-led births, there were a total of 2.6% OASI and 18.9% intact perineum.

RESULTS

The sample consisted of 757 women, 12.7% suffered OASI and 87.3% of participating women had an intact perineum. This selected sample compares the most serious outcome (OASI), and the optimal outcome (intact perineum).In primiparous women, 61 women suffered OASI and 68 women had intact perineum, while for multipara women, 35 women suffered OASI and 593 women had intact perineum. There was an increased risk of OASI if women actively pushed when the head was crowning compared to breathing the head out (adjusted OR: 3.10; 95% CI: 1.75 to 5.47). The maternal birth position associated with the lowest risk of OASI was kneeling position (adjusted OR: 0.15; 95% CI: 0.03 to 0.70), supine maternal birth position (adjusted OR: 2.52; 95% CI: 1.04 to 4.90) and oxytocin augmentation more than 30 min in second stage (OR: 1.93; 95% CI: 1.68 to 15.63) were associated with an increased risk of OASI, when adjusting for maternal, foetal, and obstetric factors.

CONCLUSION

Our study suggests that actively pushing when the baby's head is crowning, a supine maternal birth position and oxytocin augmentation more than 30 min in second stage, were associated with increased risk of OASI when compared to intact perineum. A kneeling maternal birth position was associated with a decreased risk of OASI.

Prospective comparison of obstetric anal sphincter injury incidence between an Asian and Western hospital

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injury (OASIS) rates are reported to be higher in Asian women living in Western countries than in those living in Asia, but the reasons for the differences remain unclear. The objectives of this study were for a single examiner to prospectively compare OASIS rates in primiparous Asian women in an Asian and Western birth unit and determine potential birth factors that may influence the possible difference in OASIS incidence.

METHODS

This was a prospective observational study based in Hong Kong, China, and Sydney, Australia, involving primiparous women > 36 weeks gestation of Asian descent undergoing vaginal delivery. A single examiner recorded basic patient demographics, observed all the deliveries at both sites, noting birthing techniques, and then examined the women, including a rectal examination, to determine OASIS incidence.

RESULTS

Seventy births in Hong Kong and 66 in Sydney were studied. The incidence of OASIS was 34% in Sydney and 10% in Hong Kong (p = 0.001). Birthweight, epidural rate, body mass index, and instrumental delivery were higher in Sydney. Episiotomy rates were higher in Hong Kong (59.2% vs. 82.9%; p = 0.007). When comparing OASIS with no-OASIS, perineal length (OR = 0.36, 95% CI 0.17 to 0.76, p = 0.004) and birthweight (OR = 1.14, 95% CI 1.00 to 1.30, p = 0.039) were independent risk factors for OASIS.

CONCLUSIONS

The incidence of OASIS in Asian women is significantly higher in a Western than in an Asian setting. In Asian women, perineal length and birthweight can affect the risk of OASIS at the time of vaginal delivery.

Anal Sphincter Injuries After Operative Vaginal Versus Spontaneous Delivery-Is There a Difference in Postpartum Symptoms?

OBJECTIVE

The aim of this study was to determine whether there is a difference in pelvic floor symptoms between women who had obstetric anal sphincter injuries (OASIS) after an operative vaginal delivery versus those who had OASIS after a spontaneous delivery.

METHODS

This was a secondary analysis of a prospective cohort study of women who sustained OASIS. Women were evaluated at 1 week postpartum and again at 12 weeks; at both of these visits, they completed a battery of validated questionnaires including a visual analog scale for pain, Patient Health Questionnaire 9 depression inventory, Fecal Incontinence Severity Index, Urogenital Distress Inventory 6, and Incontinence Impact Questionnaire 7.

RESULTS

Two hundred sixty-eight women with OASIS were included in this analysis (194 operative vaginal, 74 spontaneous). Ninety-one percent of those with operative vaginal delivery had a forceps-assisted delivery. After multivariate regression, operative OASIS was independently associated with greater Urogenital Distress Inventory 6 scores (P = 0.02), Fecal Incontinence Severity Index scores (P = 0.04), and visual analog scale pain scores (P = 0.03) and higher rates of urgency urinary incontinence (P = 0.04), stress urinary incontinence (P = 0.02), and anal incontinence (P = 0.04) at 1 week postpartum. At 3 months postpartum, symptoms were no different between the groups.

CONCLUSIONS

Women who sustain OASIS secondary to operative vaginal delivery report more bothersome urinary symptoms and higher rates of anal incontinence immediately postpartum as compared with women with OASIS secondary to spontaneous delivery. These differences may resolve by 3 months postpartum.

Risk of obstetric anal sphincter injury increases with maternal age irrespective of parity: a population-based register study

Background

Obstetric anal sphincter injury (OASI) is a rare but serious outcome of vaginal birth. Based on concerns about the increasing number of women who commence childbearing later than previous generation, this study aimed at investigating age-related risk of OASI in women of different parity.

Methods

A population-based register study including 959,559 live singleton vaginal births recorded in the Swedish Medical Birth Register 1999 to 2011. In each parity group risks of OASI at age 25–29 years, 30–34 years, and ≥35 years compared with age < 25 years were investigated by logistic regression analyses, adjusted for year of birth, education, region of birth, smoking, Body Mass Index, infant birthweight and fetal presentation; and in parous women, history of OASI and cesarean section. Additional analyses also adjusted for mediating factors, such as epidural analgesia, episiotomy, and instrumental delivery, and maternal age-related morbidity.

Results

Rates of OASI were 6.6%, 2.3% and 0.9% in first, second and third births respectively. Age-related risk increased from 25-29 years in first births (Adjusted OR 1.66; 95% CI 1.59–1.72) and second births (Adjusted OR 1.78; 95% CI 1.58–2.01), and from 30-34 years in third births (Adjusted OR 1.60; 95% CI 1.00–2.56). In all parity groups the risk was doubled at age ≥ 35 years, compared with the respective reference group of women under 25 years. Adding mediating factors and maternal age-related morbidity only marginally reduced these risk estimates.

Conclusion

Maternal age is an independent risk factor for OASI in first, second and third births. Although age-related risks by parity are relatively similar, more nulliparous than parous women will be exposed to OASI due to the higher baseline rate.

Electronic supplementary material

The online version of this article (10.1186/s12884-017-1473-7) contains supplementary material, which is available to authorized users.

The association between maternal age at first delivery and risk of obstetric trauma

BACKGROUND

There are a number of poor birth outcomes with advancing maternal age. Although there is some evidence of a higher risk of trauma to obstetric anal sphincter and the levator ani muscle with advancing age, findings to date are inconclusive.

OBJECTIVE

The aim of this study was to assess the risk of pelvic floor injury using translabial 3- and 4-dimensional ultrasound relative to advancing maternal age in primiparous women after a singleton vaginal delivery at term and to determine any association between maternal age and obstetric trauma, including obstetric anal sphincter injuries, levator avulsion, and irreversible overdistension of the levator hiatus.

STUDY DESIGN

This is a subanalysis of a perinatal intervention trial conducted in a specialist urogynecology referral unit at 2 tertiary units. All primiparous women with singleton birth at term underwent 3- and 4-dimensional translabial pelvic floor ultrasound both ante- and postnatally for the assessment of the obstetric trauma including levator ani muscle avulsion, hiatal overdistension to 25 cm(2) or more, and obstetric anal sphincter injuries. A multivariate logistic regression analysis was performed to examine the association between maternal age and obstetric trauma diagnosed on 3- and 4-dimensional translabial ultrasound. Multiple confounders were included, and the most significant (forceps and vacuum delivery) were used for probability modeling.

RESULTS

Of 660 women recruited for the original study, a total of 375 women who had a vaginal delivery with complete data sets were analyzed. A total of 174 women (46.4%) showed evidence of at least 1 form of major pelvic floor trauma. Advancing maternal age at first delivery carries with it a significant incremental risk of major pelvic floor trauma with an odds ratio of 1.064 for overall risk of injury for each increasing year of age past age 18 years (P = .003). The probability of any type of trauma appears to be substantially higher for forceps delivery. Vacuum delivery appears to increase the risk of obstetric anal sphincter injuries but not of levator avulsion.

CONCLUSION

There is a significant association between the risk of major pelvic floor injury and increasing maternal age at first delivery.

Obstetric anal sphincter injuries after episiotomy: systematic review and meta-analysis

Introduction

There is conflicting evidence on whether mediolateral episiotomy (MLE) reduces the risk of obstetric anal sphincter injuries (OASI) in spontaneous vaginal deliveries (SVD).

Objectives

A systematic review was undertaken to compare rates of OASI amongst women who had undergone mediolateral episiotomy versus those who did not.

Methods

ᅟ

Search strategy

Electronic searches were performed in literature databases: CINAHL, Cochrane, EMBASE, Medline and MIDIRS from database inception to July 2015. Studies were eligible if MLE was compared to spontaneous tears and if OASI was the outcome of interest.

Two reviewers independently selected and extracted data on study characteristics, quality and results. We computed events of OASI in those who did and did not have an episiotomy from individual studies and pooled these results in a meta-analysis where possible.

Main results

Of the 2090 citations, 16 were included in the review. All were non-randomised, population based or retrospective cohort studies. There was great variation in quality amongst these studies. Data from 7 studies was used for meta-analysis. On collating data from these studies where the majority of women (636755/651114) were nulliparous, MLE reduced the risk of OASI (RR 0.67 95 % CI 0.49-0.92) in vaginal delivery.

Conclusion

The pooled analysis of a large number of women undergoing vaginal birth, most of who were nulliparous, indicates that MLE has a beneficial effect in prevention of OASI. An accurately given MLE might have a role in reducing OASI and should not be withheld, especially in nulliparous women. Caution is advised as the data is from non-randomised studies.

Risk factors for recurrent obstetric anal sphincter injury (rOASI): a systematic review and meta-analysis

Objectives

The objective of this study was to estimate the risk of recurrent obstetric anal sphincter injury (rOASI) in women who have suffered anal sphincter injury in their previous pregnancy and analyse risk factors for recurrence through a systematic review and meta-analysis.

Data sources

A review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Searches were made in Ovid MEDLINE (1996 to May 2015), PubMed, EMBASE and Google Scholar, including bibliographies and conference proceedings.

Methods of study selection

Observational studies (cohort/case–control) evaluating rOASI and risk factors were selected by two reviewers who also analysed methodological quality of those studies. Pooled odds ratios (OR) for rOASI and individual risk factors were calculated using RevMan 5.3.

Tabulation, integration and results

From the eight studies assessed, overall risk of rOASI was 6.3 % compared with a 5.7 % risk of OASI in the first pregnancy. The risk in parous women with no previous OASI was 1.5 %. Factors that increased the risk in a future pregnancy were instrumental delivery with forceps [OR 3.12, 95 % confidence interval (CI) 2.42–4.01) or ventouse (OR 2.44, 95 % CI 1.83–3.25), previous fourth-degree tear (OR 1.7, 95 % CI 1.24–2.36) and birth weight ≥4 kg (OR 2.29, 95 % CI 2.06–2.54). Maternal age ≥35 years marginally increased the risk (OR 1.16, 95 % CI 1–1.35).

Conclusion

The overall rate of rOASI and associated risk factors for recurrence are similar to the rate and risk factors of primary OASI. Antenatal decisions could be based on assessment of foetal weight and intrapartum decisions based upon the requirement for an instrumental delivery.

Electronic supplementary material

The online version of this article (doi:10.1007/s00192-015-2893-4) contains supplementary material, which is available to authorized users.

A retrospective study on perineal lacerations in vaginal delivery and the individual performance of experienced mifwives

BACKGROUND

Medical staff's influence on patient outcomes has become a subject of interest. We evaluated experienced midwives and compared their performance concerning perineal lacerations (PL).

METHODS

In a retrospective cohort study, 1937 women with singleton pregnancies who had delivered spontaneously with a cephalic presentation by experienced midwives in the Medical University of Vienna from January 2009 to April 2014 were included. As predictive parameters, we included basic patient-, pregnancy- and delivery-related characteristics including the individual midwife who delivered the child. The incidence of PL was the main outcome measure.

RESULTS

Overall PL and severe PL were found in 508/1937 (26.2%) and 19/1937 women (1.0%), respectively. In a multivariate analysis for PL of any degree, maternal age (ß = 0.170 ± 0.080), gestational age at delivery (ß = 0.190 ± 0.320), and birth weight (ß = 0.002 ± 0.000) significantly increased the risk, whereas multiparity (ß = -0.379 ± 0.141) and mediolateral episiotomy (ß = -1.514 ± 0.284) decreased it (p < 0.05). In addition, the individual midwife who delivered the child was a significant influencing factor, with ß-values ranging from -0.028 to 0.899 compared to the reference midwife. For severe PL, the midwife was not of significant influence.

CONCLUSIONS

The individual midwife is an independent factor that influences the risk for overall PL, not for severe PL. Other risk factors include maternal age, gestational age at delivery, birth weight, parity and episiotomy.

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.

Obstetric perineal injury: risk factors and prevalence in a resource-constrained setting

The prevalence of obstetric perineal injuries and risk factors vary between affluent and resource-constrained settings. This prospective observational study reports on the factors associated with perineal lacerations in a cohort of Black African and Indian women delivering at two regional hospitals in South Africa. Binary logistic regression analysis was used to test for associations between independent variables and the dependent variable on multivariate analysis. All variables significant on bivariate analysis ( P < 0.05) were included in the multivariate model. There were 202 (16.2%) perineal tears. Variables significant with having a perineal tear on bivariate and multivariate analysis included: Black African race (OR: 2.4; 95% CI: 1.2–4.6); duration of labour ≥6.3h (OR: 1.5; 95% CI: 1.1–2.1); and epidural analgesia (OR: 2.9; 95% CI: 1.9–4.7). Having an episiotomy was protective against perineal tears (OR: 0.06; 95% CI: 0.03–0.1). Obstetric perineal injury commonly occurs in our resourced-constrained setting and the risk factors are similar to those in well-resourced settings. Identification of those at risk may reduce obstetric perineal injury.

Obstetric anal sphincter injury rates among primiparous women with different modes of vaginal delivery

OBJECTIVE

To determine whether rates of obstetric anal sphincter injuries (OASIS) are continuing to increase and whether risk of OASIS according to mode of delivery is constant over time.

METHODS

In a retrospective population-based study, data were obtained for vaginal singleton vertex deliveries at 37-41 weeks of pregnancy among primiparous women in New South Wales, Australia, between January 2001 and December 2011. Annual OASIS rates were determined among non-instrumental, forceps, and vacuum deliveries with and without episiotomy. Multivariable logistic regression was used to determine adjusted odds ratios for each delivery mode category by year. Trends in adjusted odds ratios over time for each delivery category were compared.

RESULTS

OASIS occurred in 955 (4.1%) of 23 081 deliveries in 2001 and 1487 (5.9%) of 25 081 deliveries in 2011. After adjustment for known risk factors, the only delivery categories to show statistically significant increases in OASIS over the study period were non-instrumental deliveries without episiotomy (linear trend P<0.001) and forceps deliveries with episiotomy (linear trend P=0.004).

CONCLUSION

Overall, OASIS rates have continued to increase. Known risk factors do not fully explain the increase in OASIS rates in non-instrumental deliveries without an episiotomy and in forceps deliveries with an episiotomy.

Is the risk of obstetric anal sphincter injuries increased in vaginal twin deliveries?

OBJECTIVE

Vaginal twin deliveries have a higher rate of intrapartum interventions. We aimed to determine whether these characteristics are associated with an increased rate of obstetric anal sphincter injuries compared with singleton.

STUDY DESIGN

Retrospective study of all twin pregnancies undergoing vaginal delivery trial was conducted from January 2000-September 2014. Sphincter injury rate compared with all concurrent singleton vaginal deliveries. Multivariable analysis was used to determine twin delivery association with sphincter injuries while adjusting for confounders.

RESULTS

About 717 eligible twin deliveries. Outcome was compared with 33 886 singleton deliveries. Twin pregnancies characterized by a higher rate of nulliparity (54.8% versus 49.5%, p = 0.005), labor induction (42.7% versus 29.1%, p < 0.001), and instrumental deliveries (27.5% versus 16.7%, p < 0.001), lower gestational (34.6 ± 3.3 versus 38.8 ± 2.3, p < 0.001), and lower birth weight. Total breech extraction was performed in 29.0% (208/717) of twin deliveries. Overall obstetric sphincter injury rate was significantly lower in the twins group (2.8% versus 4.4%, p = 0.03, OR = 0.6, 95% CI 0.4-0.9), due to lower rate of 3rd degree tears in twins versus singletons (2.2% versus 4.0%, p = 0.02), rate of 4th degree tears similar among the groups (0.6% versus 0.4%, p = 0.5). In multivariable analysis, sphincter injuries were associated with nulliparity (OR = 3.9, 95% CI 3.4-4.5), forceps (OR = 6.8, 95% CI 5.8-7.8), vacuum (OR = 2.9, 95% CI 2.5-3.3), earlier gestational age (OR = 0.2, 95% CI 0.1-0.3), episiotomy (OR = 0.8, 95% CI 0.7-0.9), and birth weight over 3500 g (OR = 1.8, 95% CI 1.6-2.0). However, the association between twins (versus singletons) deliveries and sphincter injuries was lost after adjustment for delivery gestational age (OR = 0.7, 95% CI 0.4-1.2).

CONCLUSION

Despite a higher rate of intrapartum interventions, the rate of sphincter injuries is lower in twins versus singleton deliveries, mainly due to a lower gestational age at delivery.

Obstetric anal sphincter injuries: review of anatomical factors and modifiable second stage interventions

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injuries (OASIs) are the leading cause of anal incontinence in women. Modification of various risk factors and anatomical considerations have been reported to reduce the rate of OASI.

METHODS

A PubMed search (1989-2014) of studies and systematic reviews on risk factors for OASI.

RESULTS

Perineal distension (stretching) of 170 % in the transverse direction and 40 % in the vertical direction occurs at crowning, leading to significant differences (15-30°) between episiotomy incision angles and suture angles. Episiotomies incised at 60° achieve suture angles of 43-50°; those incised at 40° result in a suture angle of 22°. Episiotomies with suture angles too acute (<30°) and too lateral (>60°) are associated with an increased risk of OASI. Suture angles of 40-60° are in the safe zone. Clinicians are poor at correctly estimating episiotomy angles on paper and in patients. Sutured episiotomies originating 10 mm away from the midline are associated with a lower rate of OASIs. Compared to spontaneous tears, episiotomies appear to be associated with a reduction in OASI risk by 40-50 %, whereas shorter perineal lengths, perineal oedema and instrumental deliveries are associated with a higher risk. Instrumental deliveries with mediolateral episiotomies are associated with a significantly lower OASI risk. Other preventative measures include warm perineal compresses and controlled delivery of the head.

CONCLUSIONS

Relieving pressure on the central posterior perineum by an episiotomy and/or controlled delivery of the head should be important considerations in reducing the risk of OASI. Episiotomies should be performed 60° from the midline. Prospective studies should evaluate elective episiotomies in women with a short perineal length and application of standardised digital perineal support.

Perineal management techniques among midwives at five hospitals in New South Wales - a cross-sectional survey

BACKGROUND

Midwives are reported to have changed from 'hands on' to 'hands poised or off' approaches to birth at the same time as obstetric anal sphincter injuries (OASIs) are increasing. As perineal management details are not routinely collected, it is difficult to quantify practice.

AIMS

To determine which perineal protections techniques midwives prefer for low-risk non-water births; whether preference is associated with technique taught or with other characteristics; and whether midwives change preference according to clinical scenario.

MATERIALS AND METHODS

Midwives in Northern Sydney Local Health District (NSLHD) were surveyed during a 2-week period in 2014. Multiple-choice questions were used, with free text option. Descriptive analyses, chi-square and McNemar tests were undertaken.

RESULTS

One hundred and eight midwives participated (response rate 76.7%). 'Hands poised or off' was preferred by 63.0% for a low-risk birth. Current practice was associated with technique taught (P < 0.01). For scenarios with increased OASI risk midwives reported switching to 'hands on', with 83.4% employing 'hands on' whether there was concern about an impending OASI. There has been a shift over time from teaching 'hands on' to 'hands poised or off'.

CONCLUSION

The preferred technique for a low-risk birth appears to have changed from 'hands on' to 'hands poised or off', but most midwives adopt 'hands on' in situations of high risk for OASI. Further research is needed to establish whether there is an association with the rising OASI rate and the change in preferred perineal management technique for a low-risk birth.

Knowledge, attitude and experience of episiotomy use among obstetricians and midwives in Viet Nam

Background

Episiotomy remains a routine procedure at childbirth in many South-East Asian countries but the reasons for this are unknown. The aim of this study was to determine the knowledge of, attitudes towards and experience of episiotomy use among clinicians in Viet Nam.

Methods

All obstetricians and midwives who provide delivery care at Hung Vuong Hospital were surveyed about their practice, knowledge and attitudes towards episiotomy use. Data were analysed using frequency tabulations and contingency table analysis.

Results

148 (88%) clinicians completed the questionnaire. Fewer obstetricians (52.2%) than midwives (79.7%) thought the current episiotomy rate of 86% was about right (P < 0.01). Most obstetricians (82.6%) and midwives (98.7%) reported performing episiotomies on nulliparous women over 90% of the time. Among multipara, 24.6% of obstetricians reported performing episiotomy less than 60% of the time compared with only 3 (3.8%) midwives (P < 0.01). Aiming to reduce 3rd-4th degree perineal tears was the most commonly reported reason for performing an episiotomy by both obstetricians (76.8%) and midwives (82.3%), and lack of training in how to minimize tears and keep the perineum intact was the mostly commonly reported obstacle (obstetricians 56.5%, midwives 36.7% P = 0.02) to reducing the episiotomy rate.

Conclusion

Although several factors that may impede or facilitate episiotomy practice change were identified by our survey, training and confidence in normal vaginal birth without episiotomy is a priority.