Can the risk of obstetric anal sphincter injuries (OASIs) be predicted using a risk-scoring system?

The association between waterbirth and perineal injury or other adverse outcomes among low-risk women with physiological birth: Results from the Nordic Home Birth Cohort Study

PROBLEM/BACKGROUND

Immersion in water has known benefits, such as reducing pain and shortening the duration of labour. The relationship between waterbirth and perineal injury remains unclear.

AIM

To compare the incidence of perineal injury in waterbirth and birth on land among low-risk women. Secondary outcomes were postpartum haemorrhage and 5-minute Apgar scores <7.

METHODS

Prospective cohort study of 2875 low-risk women who planned a home birth in Denmark, Iceland, Norway, and Sweden in 2008-2013 and had a spontaneous vaginal birth without intervention. Descriptive statistics and logistic regression were performed.

FINDINGS

A total of 942 women had a waterbirth, and 1933 gave birth on land. The groups differed in their various background variables. Multiparous women had moderately lower rates of intact perineum (59.3% vs. 63.9%) and primiparous women had lower rates of episiotomies (1.1% vs. 4.8%) in waterbirth than in birth on land. No statistically significant differences were detected in adjusted regression analysis on intact perineum in waterbirth (primiparous women's aOR = 1.03, CI 0.68-1.58; multiparous women's aOR = 0.84, CI 0.67-1.05). The rates of sphincter injuries (0.9% vs. 0.6%) were low in both groups. No significant differences were detected in secondary outcomes.

DISCUSSION

The decreased incidence of intact perineum among multiparous women was modest and inconclusive, and the prevalence of sphincter injury was low.

CONCLUSION

Low-risk women contemplating waterbirth should be advised to weigh the risks and benefits detected in this study against previously established benefits of waterbirth and should make an informed choice based on their values.

The prevention of perineal trauma during vaginal birth

Perineal trauma after vaginal birth is common, with approximately 9 of 10 women being affected. Second-degree perineal tears are twice as likely to occur in primiparous births, with a incidence of 40%. The incidence of obstetrical anal sphincter injury is approximately 3%, with a significantly higher rate in primiparous than in multiparous women (6% vs 2%). Obstetrical anal sphincter injury is a significant risk factor for the development of anal incontinence, with approximately 10% of women developing symptoms within a year following vaginal birth. Obstetrical anal sphincter injuries have significant medicolegal implications and contribute greatly to healthcare costs. For example, in 2013 and 2014, the economic burden of obstetrical anal sphincter injuries in the United Kingdom ranged between £3.7 million (with assisted vaginal birth) and £9.8 million (with spontaneous vaginal birth). In the United States, complications associated with trauma to the perineum incurred costs of approximately $83 million between 2007 and 2011. It is therefore crucial to focus on improvements in clinical care to reduce this risk and minimize the development of perineal trauma, particularly obstetrical anal sphincter injuries. Identification of risk factors allows modification of obstetrical practice with the aim of reducing the rate of perineal trauma and its attendant associated morbidity. Risk factors associated with second-degree perineal trauma include increased fetal birthweight, operative vaginal birth, prolonged second stage of labor, maternal birth position, and advanced maternal age. With obstetrical anal sphincter injury, risk factors include induction of labor, augmentation of labor, epidural, increased fetal birthweight, fetal malposition (occiput posterior), midline episiotomy, operative vaginal birth, Asian ethnicity, and primiparity. Obstetrical practice can be modified both antenatally and intrapartum. The evidence suggests that in the antenatal period, perineal massage can be commenced in the third trimester of pregnancy to increase muscle elasticity and allow stretching of the perineum during birth, thereby reducing the risk of tearing or need for episiotomy. With regard to the intrapartum period, there is a growing body of evidence from the United Kingdom, Norway, and Denmark suggesting that the implementation of quality improvement initiatives including the training of clinicians in manual perineal protection and mediolateral episiotomy can reduce the incidence of obstetrical anal sphincter injury. With episiotomy, the International Federation of Gynecology and Obstetrics recommends restrictive rather than routine use of episiotomy. This is particularly the case with unassisted vaginal births. However, there is a role for episiotomy, specifically mediolateral or lateral, with assisted vaginal births. This is specifically the case with nulliparous vacuum and forceps births, given that the use of mediolateral or lateral episiotomy has been shown to significantly reduce the incidence of obstetrical anal sphincter injury in these groups by 43% and 68%, respectively. However, the complications associated with episiotomy including perineal pain, dyspareunia, and sexual dysfunction should be acknowledged. Despite considerable research, interventions for reducing the risk of perineal trauma remain a subject of controversy. In this review article, we present the available data on the prevention of perineal trauma by describing the risk factors associated with perineal trauma and interventions that can be implemented to prevent perineal trauma, in particular obstetrical anal sphincter injury.

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.

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 Flexible Sacrum Position on Maternal and Neonatal Outcomes in Public Health Facilities, Amhara Regional State, Ethiopia: A Quasi-Experimental Study

Restricting women giving birth in health care facilities from choosing the most comfortable position during labor and birth is a global problem. This study was aimed to examine the effect of flexible sacrum birth positions on maternal and neonatal outcomes in public health facilities in Ethiopia's Amhara Region. A non-equivalent control group post-test-only design was employed at public health facilities from August to November 2019. A total of 1048 participants were enrolled and assigned to intervention or control groups based on their choice of birth position. Participants who preferred the flexible sacrum birth position received the intervention, while participants who preferred the supine birth position were placed in the control group. Data were collected using observational follow-up from admission to immediate postpartum period. Log binomial logistic regression considering as treated analysis was used. Of the total participants, 970 women gave birth vaginally, of whom 378 were from the intervention group, and 592 were from the control group. The intervention decreased the chance of perineal tear and poor Apgar score by 43 and 39%, respectively. The flexible sacrum position reduced the duration of the second stage of labor by a mean difference of 26 min. Maternal and newborn outcomes were better in the flexible sacrum position.

Do doctors preferring forceps encounter more obstetric anal sphincter injuries: A retrospective analysis

BACKGROUND

Obstetric anal sphincter injuries (OASIS) is a hospital-acquired injury and can affect a woman's quality of life with problems such as anal incontinence, perineal pain, dyspareunia, mental health, psychosexual issues, and concerns about future childbirth choices.

AIMS

The aim of this study was to determine whether there is a correlation between a doctor's preference for instruments, their individual OASIS rate and whether factors such as their fully dilated caesarean section rate, rate of double instrumental and seniority, influences their individual rate of OASIS.

MATERIALS AND METHODS

A population-based retrospective cohort study was performed on 1340 term nulliparous women with singleton pregnancies who underwent an instrumental delivery or fully dilated caesarean section. A survey of doctors involved in these deliveries was performed. The risk of OASIS was analysed for maternal age, ethnicity, birth position, level of training and doctor's instrument preference using a generalised linear mixed model. Doctors' instrument preferences were established in two ways: a self-reported survey and data-inferred preference based on the most used instrument per doctor. The OASIS rate for individual doctors was calculated.

RESULTS

The overall risk of OASIS is higher for forceps compared to vacuum deliveries. Doctors with a preference for forceps compared to vacuum, correlated with both a lower OASIS rate and a higher fully dilated caesarean section rate.

CONCLUSIONS

Doctors preferring forceps report a lower OASIS and higher fully dilated caesarean section rate. Doctors preferring vacuum must consider carefully whether forceps should follow if a vacuum fails as OASIS is more likely to occur.

The clinical progression and wound healing rate of dehisced perineal tears healing by secondary intention: A prospective observational study

OBJECTIVES

To establish the clinical progression of dehisced perineal wounds healing by secondary intention and to investigate the incidence and factors associated with delayed healing.

METHODS

Secondary analysis of women with perineal wound dehiscence recruited into the PERINEAL study between August 2020- August 2021 (NCT04480684). Three-dimensional wound measurements were taken with the Silhouette® camera. Significant bacterial colonisation was diagnosed using the MolecuLight i:X camera. As it is agreed that acute wounds should heal sufficiently within four weeks, diagnosis of delayed wound healing was made if a wound took longer than four weeks to heal. A wound was deemed to have healed if there was complete wound closure, with no evidence of granulation tissue or signs of infection on clinical examination.

RESULTS

55 women with perineal wound dehiscence participated. Wounds took an average of 3 weeks to heal (range 1-16) and 38 (69.1%) wounds healed in ≤ 4 weeks from the first clinical review. 17 (30.9%) wounds had significant bacterial colonisation, identified on bacterial fluorescence imaging. Women with a wound area of < 1.60 cm² or wound perimeter of < 5.57 cm had a 70% probability of wound healing in ≤ 4 weeks. 47.1% of wounds with significant bacteria colonisation healed within 4 weeks, in comparison to 78.9% of wounds not colonised (p = 0.03). 25.0 % (n = 2) of wounds with OASI healed within 4 weeks, in comparison to 76.5% (n = 36) of wounds with no OASI (p = 0.02). Bacterial fluorescence (OR 0.21 (0.05-0.87)) and OASIs (OR 0.09 (0.01-0.66)) were independent risk factors associated with delayed wound healing. The model including wound area, fluorescence and OASIs had the greatest AUC (0.81, 95% CI 0.67-0.94) indicating the best predictive model.

CONCLUSIONS

This is the first study to describe healing outcomes of dehisced perineal wounds and factors associated with delayed healing. The study findings will help clinicians counsel women effectively and tailor follow-up care at the first assessment, based on individual risk factors.

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..

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.

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.

How can we improve our practices in obstetric anal sphincter injury prevention, diagnosis, and management of symptomatic women?

Obstetric anal sphincter injury (OASI) is strongly associated with a major negative impact on women's health. Due to the consequences of an undiagnosed and therefore unrepaired OASI, it is essential to prevent or at least diagnose OASI at childbirth. We need to promote training of professionals to improve OASI screening at childbirth. High-risk situations such as operative delivery must be identified and preventive strategies such as the choice of a less traumatic instrument (vacuum) and mediolateral episiotomy should be considered. For a woman with OASI and/or symptoms, postnatal consultation with a specialist on pelvic floor disorders is essential to correctly orient her toward an adequate care pathway and to eventually identify occult or underestimated OASI. More data are required on therapeutic approaches for symptomatic women, primarily including physical therapy, sacral neuromodulation, delayed sphincter repair and palliative devices.

A retrospective study of the incidence and predisposing factors of third- and fourth-degree perineal tears

OBJECTIVES

To evaluate the rates of third- and fourth-degree tears and related predisposing factors for the tears in singleton vaginal deliveries. Methods: This was a retrospective study of third- and fourth-degree perineal tears in all women who underwent vaginal delivery in a tertiary hospital in Assir region between January 2014 and December 2019. There are approximately 5000 deliveries per year at the Abha Maternity and Children Hospital. The total number of deliveries during the study period was 31,788, of which 19,374 were delivered vaginally. Results: A total of 85 women (0.43% of all vaginal deliveries) had third-degree (n=81) or fourth-degree (n=4) perineal tears. The mean age of the women was 31 years (range: 16-46 years). Fifty-two of the 85 women (61%) were primiparous. Of the various obstetric parameters, episiotomy, occipitoposterior presentation, primigravida, multipara, and a previous episiotomy were found to be significant predisposing factors to third- and fourth-degree tears in our patients.

CONCLUSION

The low incidence of obstetric anal sphincter injuries in this study is likely the result of proactive manual protection of the perineum, valid indications for episiotomy, and attendance of senior staff members at all difficult deliveries.

The association between sonographic fetal head circumference, obstetric anal sphincter injury and mode of delivery: A retrospective cohort study

BACKGROUND

There is no consensus to the implications of an increased sonographic fetal head circumference (HC) and its impact on delivery.

AIM

To examine if there is any association between sonographic fetal HC, obstetric anal sphincter injury (OASIS) and mode of delivery.

MATERIALS AND METHODS

A retrospective cohort study of term, singleton births between April 2017 and March 2019 at a large regional hospital in Australia with a third trimester ultrasound. Logistic regressions were performed investigating sonographic fetal HC and additional risk factors for OASIS. Further multinomial logistic regressions assessed the relationship between the sonographic HC and mode of delivery. Odds ratios and their 95% CIs were reported.

RESULTS

Of 667 eligible women, 487 (73%) had vaginal births, with 32 (6.6%) sustaining an OASIS and 180 (27%) had caesarean sections (CS). The sonographic fetal HC did not show an association with OASIS (odds ratio 1.005; CI 0.99-1.01, P = 0.447). A statistically significant association (P < 0.05) with OASIS was found with Asian ethnicity (4.38; 1.5-11.32), prolonged second stage (≥2 h) (4.26; 1.57-10.49) and occiput posterior position (4.01; 1.08-11.92). For women with a sonographic fetal HC ≥ 90th percentile, the odds of having CS compared to a spontaneous vaginal birth are 2.77 (95% CI: 1.36, 5.62; P = 0.005) times higher than those who have a HC < 90th percentile.

CONCLUSION

This study does not support the use of sonographic fetal HC in assessing a woman's risk of sustaining an OASIS. Sonographic fetal HC is associated with mode of delivery.

Waterbirth: a national retrospective cohort study of factors associated with its use among women in England

Background

Waterbirth is widely available in English maternity settings for women who are not at increased risk of complications during labour. Immersion in water during labour is associated with a number of maternal benefits. However for birth in water the situation is less clear, with conclusive evidence on safety lacking and little known about the characteristics of women who give birth in water.

This retrospective cohort study uses electronic data routinely collected in the course of maternity care in England in 2015–16 to describe the proportion of births recorded as having occurred in water, the characteristics of women who experienced waterbirth and the odds of key maternal and neonatal complications associated with giving birth in water.

Methods

Data were obtained from three population level electronic datasets linked together for the purposes of a national audit of maternity care. The study cohort included women who had no risk factors requiring them to give birth in an obstetric unit according to national guidelines. Multivariate logistic regression models were used to examine maternal (postpartum haemorrhage of 1500mls or more, obstetric anal sphincter injury (OASI)) and neonatal (Apgar score less than 7, neonatal unit admission) outcomes associated with waterbirth.

Results

46,088 low and intermediate risk singleton term spontaneous vaginal births in 35 NHS Trusts in England were included in the analysis cohort. Of these 6264 (13.6%) were recorded as having occurred in water. Waterbirth was more likely in older women up to the age of 40 (adjusted odds ratio (adjOR) for age group 35–39 1.27, 95% confidence interval (1.15,1.41)) and less common in women under 25 (adjOR 18–24 0.76 (0.70, 0.82)), those of higher parity (parity ≥3 adjOR 0.56 (0.47,0.66)) or who were obese (BMI 30–34.9 adjOR 0.77 (0.70,0.85)). Waterbirth was also less likely in black (adjOR 0.42 (0.36, 0.51)) and Asian (adjOR 0.26 (0.23,0.30)) women and in those from areas of increased socioeconomic deprivation (most affluent versus least affluent areas adjOR 0.47 (0.43, 0.52)).

There was no association between delivery in water and low Apgar score (adjOR 0.95 (0.66,1.36)) or incidence of OASI (adjOR 1.00 (0.86,1.16)). There was an association between waterbirth and reduced incidence of postpartum haemorrhage (adjOR 0.68 (0.51,0.90)) and neonatal unit admission (adjOR 0.65 (0.53,0.78)).

Conclusions

In this large observational cohort study, there was no association between waterbirth and specific adverse outcomes for either the mother or the baby. There was evidence that white women from higher socioeconomic backgrounds were more likely to be recorded as giving birth in water. Maternity services should focus on ensuring equitable access to waterbirth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-03724-6.

Prediction model for obstetric anal sphincter injury using machine learning

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injury (OASI) is a complication with substantial maternal morbidity. The aim of this study was to develop a machine learning model that would allow a personalized prediction algorithm for OASI, based on maternal and fetal variables collected at admission to labor.

MATERIALS AND METHODS

We performed a retrospective cohort study at a tertiary university hospital. Included were term deliveries (live, singleton, vertex). A comparison was made between women diagnosed with OASI and those without such injury. For formation of a machine learning-based model, a gradient boosting machine learning algorithm was implemented. Evaluation of the performance model was achieved using the area under the receiver-operating characteristic curve (AUC).

RESULTS

Our cohort comprised 98,463 deliveries, of which 323 (0.3%) were diagnosed with OASI. Applying a machine learning model to data recorded during admission to labor allowed for individualized risk assessment with an AUC of 0.756 (95% CI 0.732-0.780). According to this model, a lower number of previous births, fewer pregnancies, decreased maternal weight and advanced gestational week elevated the risk for OASI. With regard to parity, women with one previous delivery had approximately 1/3 of the risk for OASI compared to nulliparous women (OR = 0.3 (0.23-0.39), p < 0.001), and women with two previous deliveries had 1/3 of the risk compared to women with one previous delivery (OR = 0.35 (0.21-0.60), p < 0.001).

CONCLUSION

Our machine learning-based model stratified births to high or low risk for OASI, making it an applicable tool for personalized decision-making upon admission to labor.

Prospective cohort study of water immersion for labour and birth compared with standard care in an Irish maternity setting

OBJECTIVE

To examine the birth outcomes for women and babies following water immersion for labour only, or for labour and birth.

DESIGN

Prospective cohort study.

SETTING

Maternity hospital, Ireland, 2016-2019.

PARTICIPANTS

A cohort of 190 low-risk women who used water immersion; 100 gave birth in water and 90 laboured only in water. A control group of 190 low-risk women who received standard care.

METHODS

Logistic regression analyses examined associations between water immersion and birth outcomes adjusting for confounders. A validated Childbirth Experience Questionnaire was completed.

MAIN OUTCOME MEASURES

Perineal tears, obstetric anal sphincter injuries (OASI), postpartum haemorrhage (PPH), neonatal unit admissions (NNU), breastfeeding and birth experiences.

RESULTS

Compared with standard care, women who chose water immersion had no significant difference in perineal tears (71.4% vs 71.4%, adj OR 0.83; 95% CI 0.49 to 1.39) or in OASI (3.3% vs 3.8%, adj OR 0.91; 0.26-2.97). Women who chose water immersion were more likely to have a PPH ≥500 mL (10.5% vs 3.7%, adj OR 2.60; 95% CI 1.03 to 6.57), and to exclusively breastfeed at discharge (71.1% vs 45.8%, adj OR 2.59; 95% CI 1.66 to 4.05). There was no significant difference in NNU admissions (3.7% vs 3.2%, adj OR 1.06; 95% CI 0.33 to 3.42). Women who gave birth in water were no more likely than women who used water for labour only to require perineal suturing (64% vs 80.5%, adj OR 0.63; 95% CI 0.30 to 1.33), to experience OASI (3.0% vs 3.7%, adj OR 1.41; 95% CI 0.23 to 8.79) or PPH (8.0% vs 13.3%, adj OR 0.73; 95% CI 0.26 to 2.09). Women using water immersion reported more positive memories than women receiving standard care (p<0.01).

CONCLUSIONS

Women choosing water immersion for labour or birth were no more likely to experience adverse birth outcomes than women receiving standard care and rated their birth experiences more highly.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

The Incidence of and Predictors for Severe Perineal Trauma and Intact Perineum in Women Having a Waterbirth in England: A Hospital-Based Study

Background: To determine the incidence of and predictors for obstetric anal sphincter injuries (OASIS) and intact perineum in women giving birth in the water and compare with the general obstetric population. Materials and Methods: Data were retrospectively collected for women who had singleton cephalic presentation vaginal births in the water and the general obstetric population between August 2007 and December 2017. Results: We identified 1,007 women who had a waterbirth and 36,924 women from the general obstetric population. There was no significant difference in the incidence of OASIS between waterbirths and the general obstetric population (2.3% vs. 2.0%). Having a waterbirth was associated with a lower probability for an intact perineum (odds ratio [OR] = 0.83; confidence interval [95% CI]: 0.73-0.94) when compared with the general obstetric population (44.7% vs. 51.3%). Nulliparous women with a waterbirth when compared with multiparous women had an eightfold higher likelihood for the occurrence of OASIS (OR = 8.28; 95% CI: 2.64-25.86). The risk for a higher degree of OASIS was associated with increased maternal age in the total sample (OR = 1.08; 95% CI: 1.06-1.11) and with a lower body mass index (BMI) at booking in multiparous women (OR = 0.96; 95% CI: 0.92-0.99). The risk for any type of perineal trauma was associated with increased maternal age in the total sample (OR = 1.10; 95% CI: 1.07-1.13) and with a lower BMI at booking in multiparous women (OR = 0.95; 95% CI: 0.91-0.99). Conclusions: We found that giving birth in the water reduced the chance of having an intact perineum. We have also shown that nulliparity, increased maternal age in all women, and a lower BMI at booking in multiparous were associated with OASIS and lower rates of intact perineum in waterbirths.

Risk Factors for Obstetric Anal Sphincter Injuries among Women Delivering at a Tertiary Hospital in Southwestern Uganda

Background

Obstetric anal sphincter injuries (OASIS) arise from perineal trauma during vaginal delivery and are associated with poor maternal health outcomes. Most OASIS occur in unattended deliveries in resource-limited settings. However, even in facilities where deliveries are attended by skilled personnel, a number of women still get OASIS.

Objectives

To determine the incidence and risk factors for obstetric anal sphincter injuries among women delivering at Mbarara Regional Referral Hospital (MRRH).

Methods

We conducted an unmatched hospital-based case control study, with the ratio of cases to controls of 1 : 2 (80 cases and 160 controls). We defined a case as a mother who got a third- or fourth-degree perineal tear after vaginal delivery while the controls recruited were the next two mothers who delivered vaginally without a third- or fourth-degree perineal tear. A questionnaire and participants' medical records review were used to obtain sociodemographic and clinical data. We estimated the incidence of OASIS and performed univariable and multivariable logistic regression to identify the associated risk factors.

Results

The cumulative incidence for OASIS during the study period was 6.6%. The risk factors for OASIS were 2^nd stage of labour ≥1 hour (aOR 6.07, 95%CI 1.86–19.82, p=0.003), having episiotomy performed during labour (aOR 2.57, 95%CI 1.07–6.17, p=0.035), perineum support during delivery (aOR 0.03, 95%CI 0.01–0.12, p < 0.001), and monthly income of >50,000 shillings (aOR 0.09, 95%CI 0.03–0.28, p < 0.001). Conclusions and Recommendations. The risk factors for obstetric anal sphincter injury were prolonged second stage of labour and performing episiotomies during deliveries while higher monthly income and perineum support during delivery were protective. We recommend routine support to the perineum during delivery. Care should be taken in mothers with episiotomies, as they can extend and cause OASIS.

Tissue biomechanical behavior should be considered in the risk assessment of perineal trauma at childbirth

Perineal trauma at childbirth is associated with strong negative impacts on a woman's health but remains unpredictable. Pregnancy induces several changes in biomechanical behavior in humans as in animals, namely, an increase in ligamentous laxity and an increase in vaginal distensibility. Pelvic floor muscles in rats are reported to exhibit specific behaviors during pregnancy. Increases in both stiffness and the number of sarcomeres in series are observed and might process that protect against perineal trauma at childbirth. Some data in humans have shown that the risk of perineal trauma is highly linked to the intrinsic characteristics of the tissue, suggesting the potential benefit of incorporating intrinsic biomechanical characteristics in the risk prediction for perineal trauma. Shear wave elastography might be a useful noninvasive tool to investigate the elastic properties of these tissues in pregnant women in vivo, with the goal of implementing these properties as a predictive strategy.

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

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

Does water birth affect the risk of obstetric anal sphincter injury? Development of a prognostic model

INTRODUCTION AND HYPOTHESIS

Obstetric anal sphincter injury (OASI) is a significant complication of vaginal delivery. Water birth has become a popular preference for women giving birth in the UK, however, there is limited data on the risk of OASI following water birth. Our aim was to assess OASI risk in low-risk women giving birth in water without medical intervention compared with on land and to create a prognostic model for OASI prediction.

METHODS

This was a retrospective study of 15,734 low-risk women giving birth by spontaneous vaginal delivery between January 2008 and October 2014 in a midwifery-led unit (MLU). Patient factors and delivery data were analysed to identify differences between water and land births. Univariate analysis determined factors that statistically predicted OASI and was then used to create multivariate analysis. Significant multivariate factors were used to create a prognostic model to predict likelihood of OASI.

RESULTS

OASI rates were 1.6% on land and 3.3% in water [odds ratio (OR) 2.10, 95% confidence interval (CI) 1.5-2.94). Multivariate analysis confirmed water birth, ethnicity and parity as independent risk factors for OASI (adjusted OR water birth: 1.77 (CI 1.25-2.51). Our prognostic model showed Black and Asian primigravidae following water birth had the highest risk of OASI and white multiparae on land the lowest.

CONCLUSION

This study of comparable low-risk women shows an increased risk of OASI following water birth compared with land birth. Use of this prognostic model will help women determine their risk of OASI following birth in water or on land.

[Definition, epidemiology and risk factors of obstetric anal sphincter injuries: CNGOF Perineal Prevention and Protection in Obstetrics Guidelines]

OBJECTIVES

The aim of this review was to agree on a definition of the obstetric anal sphincter injuries (OASIS), to determine the prevalence and risk factors.

METHODS

A comprehensive review of the literature on the obstetric anal sphincter injuries (OASIS), establishment of levels of evidence (NP), and grades of recommendation according to the methodology of the recommendations for clinical practice.

RESULTS

To classify obstetric anal sphincter injuries (OASIS), we have used the WHO-RCOG classification, which lists 4 degrees of severity. To designate obstetric anal sphincter injuries, we have used the acronym OASIS, rather than the standard French terms of "complete perineum" and "complicated complete perineum". OASIS with only isolated involvement of the EAS (3a and 3b) appears to have a better functional prognosis than OASIS affecting the IAS or the anorectal mucosa (3c and 4) (LE3). The prevalence of women with ano-rectal symptoms increases with the severity of the OASIS (LE3). In the long term, 35-60% of women who had an OASIS have anal or fecal incontinence (LE3). The prevalence of an OASI in the general population is between 0.25 to 6%. The prevalence of OASIS in primiparous women is between 1.4 and 16% and thus, should be considered more important than among the multiparous women (0.4 to 2.7%). In women with a history of previous OASIS, the risk of occurrence is higher and varies between 5.1 and 10.7% following childbirth. The priority in this context remains the training of childbirth professionals (midwives and obstetricians) to detect these injuries in the delivery room, immediately after the birth. The training and awareness of these practitioners of OASIS diagnosis improves its detection in the delivery room (LE2). Professional experience is associated with better detection of OASIS (LE3) (4). Continuing professional education of obstetrics professionals in the diagnosis and repair of OASIS must be encouraged (Grade C). In the case of second-degree perineal tear, the use of ultrasound in the delivery room improves the diagnosis of OASIS (LE2). Ultrasound decreases the prevalence of symptoms of severe anal incontinence at 1 year (LE2). The diagnosis of OASIS is improved by the use of endo-anal ultrasonography in post-partum (72h-6weeks) (LE2). The principal factors associated with OASIS are nulliparity and instrumental (vaginal operative) delivery; the others are advanced maternal age, history of OASIS, macrosomia, midline episiotomy, posterior cephalic positions, and long labour (LE2). The presence of a perianal lesion (perianal fissure, or anorectal or rectovaginal fistula) is associated with an increased risk of 4th degree lacerations (LE3). Crohn's disease without perianal involvement is not associated with an excess risk of OASIS (LE3). For women with type III genital mutilation, deinfibulation before delivery is associated with a reduction in the risk of OASIS (LE3); in this situation, deinfibulation is recommended before delivery (grade C).

CONCLUSION

It is necessary to use a consensus definition of the OASIS to be able to better detect and treat them.

A comparative study of obstetric anal sphincter injuries in vaginal deliveries of twins and singleton pregnancies

AIMS

Increasing numbers of twin pregnancies necessitate investigation of the risk factors associated with obstetric anal sphincter injuries (OASIS). The aims of this study were to establish the incidence of OASIS, and compare women delivering twins to those delivering singletons in risk of OASIS plus maternal, neonatal, and obstetric outcomes.

METHODS

A retrospective cohort study was undertaken and included women delivering in a tertiary London maternity unit between 1999 and 2015; 51 957 eligible women with singleton and 261 with twin pregnancies were identified. Women delivering twins were compared to those delivering singletons in the occurrence of maternal, neonatal, and obstetric outcomes using unadjusted relative risks. A secondary analysis was performed, and conditional logistic regression used to derive an adjusted relative risk of OASIS. Women delivering singletons were matched to those delivering twins for age, parity, ethnicity, gestation, and mode of delivery in a ratio of 2:1.

RESULTS

Compared to the singleton group, mothers delivering twins had significantly more instrumental deliveries (RR [95%CI] 1.92 [1.67-2.27]; P < 0.0001), smaller fetuses (2754.1 vs 3383.8 g; P < 0.001), and were older (32.9 vs 31.0 years; P < 0.0001). The twin group was not significantly different to the singleton group in risk of OASIS (RR 0.61 [0.27-1.33], P = 0.205). The conditional logistic regression demonstrated similar results for the risk of OASIS (adjusted RR = 0.58 [0.22-1.47]; P = 0.253).

CONCLUSIONS

Women delivering twins vaginally were not at a significantly higher risk of sustaining OASIS compared to those delivering singletons.

Third and Fourth Degree Perineal Tear in Four-Year Period at Sestre Milosrdnice University Hospital Center, Zagreb, Croatia

OBJECTIVES:

Obstetric anal sphincter injury (OASIS) includes the third and fourth degree of perineal injury. The risk for OASIS is about 1% of all vaginal deliveries. If not recognised and treated properly, obstetric anal sphincter injury can have serious consequences for reproductive age woman.

MATERIAL AND METHODS:

We have retrospectively gathered and analysed data on obstetric anal sphincter injury in a four-year period at our department. The control group in this study included vaginal deliveries in 2012.

RESULTS:

We recorded 0.34% third and fourth degree of perineal injury in all vaginal deliveries, and 87.9% of those patients were primiparae. Episiotomy was performed in 57.6% of all women with obstetric anal sphincter injury. In 30.3% of cases, newborns were large for gestational age. Gestational diabetes was found in 9.1% of OASIS cases, occipitoposterior position was found in 9.1% of cases. Induced labour took place in 39.4%, and oxytocin infusion was applied in 60.6% of OASIS cases. Vacuum extraction was performed in 12.1% of deliveries with OASIS. The average BMI in 3a and 3b injuries was 29.9. In 3c degree it was 28.0, and in the fourth degree, it was 32.1. In 27.0% of OASIS cases due to the extent of the injury surgeon engagement was necessary. When compared with vaginal deliveries in 2012 we found a significant increase in OASIS in primiparas, large for gestational age, occipitoposterior position, induced labour, vacuum extraction and hypertension (P < 0.01). There is also increased incidence of OASIS in episiotomy and oxytocin use group (P < 0.05).

CONCLUSION:

Low incidence of OASIS in our department is a result of active management of delivery, manual perineal protection and timely episiotomy.

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 incontinence and obstetrical anal sphincter injuries, epidemiology and prevention]

Our main objectives were to identify risk factors, methods for early diagnosis, and prevention of obstetric anal sphincter injuries (OASIs), using a literature review. The main risk factors for OASIs are nulliparity, instrumental delivery, posterior presentation, median episiotomy, prolonged second phase of labor and fetal macrosomia. Asian origin, short ano-vulvar distance, ligamentous hyperlaxity, lack of expulsion control, non-visualization of the perineum or maneuvers for shoulder dystocia also appear to be risk factors. There is a risk of under-diagnosis of OASIs in the labor ward. Experience of the accoucheur is a protective factor. Secondary prevention is based on the training of birth professionals in recognition and repair of OASIs. Primary prevention of OASIs is based on training in the maneuvers of the second phase of labor; if possible, instrumental extractions should be avoided. Mediolateral episiotomy may have a preventive role in high-risk OASIs deliveries. A robust predictive model is still lacking to allow a selective use of episiotomy.

Waterbirth in Sweden - a comparative study

INTRODUCTION

The literature describes advantages for mothers giving birth in water, but waterbirth is controversial in Sweden and has not been offered at hospitals until recently. This study aimed to describe and compare the characteristics and outcome of waterbirths with those of spontaneous vaginal births at the same clinics.

MATERIAL AND METHODS

A retrospective cohort study was conducted on all waterbirths at two maternity units in Sweden from March 2014 to November 2015 (n = 306), and a consecutively selected comparison group of 306 women having conventional spontaneous vaginal births. Logistic regression was used to analyze the primary outcome; second-degree perineal tears.

RESULTS

Women giving birth in water had a lower risk of second-degree perineal tears [adjusted odds ratio (aOR) 0.6, 95% confidence interval (CI) 0.4-0.9]). Their labor was shorter (6 h 3 min vs. 7 h 52 min) and there were significantly fewer interventions than in the comparison group; amniotomy (13.7 vs. 35.3%), internal cardiotocography (11.1 vs. 56.8%), and augmentation with oxytocin (5.2 vs. 31.3%). There were no differences in Apgar scores or admissions to neonatal intensive care unit. The experience of childbirth, measured with a numeric rating scale, was higher in the waterbirth group indicating a more positive birth experience. Three newborns born in water had an umbilical cord avulsion.

CONCLUSIONS

In this low-risk population, waterbirth is associated with positive effects on perineal tears, the frequency of interventions, the duration of labor and women's birth experience. Midwives handling waterbirth should be aware of the risk of umbilical cord avulsion.

Incidence and risk factors of third- and fourth-degree perineal tears in a single Italian scenario

OBJECTIVE

This study aimed to evaluate III and IV degree tears rates and related risk factors in a single Italian centre. The secondary goal was to build a predictive model based on identified risk factors.

STUDY DESIGN

This was a retrospective cohort study. All vaginal deliveries from 2011 to 2015 in a single Italian University Hospital were analysed. Univariate analysis was applied to evaluate the overall association between each factor and severe tear. Multivariate logistic regression was used to build a predictive model for the absolute risk of severe tear. We computed a resampling validated measure (AUC) of the predictive accuracy of the model and we provided a nomogram for the risk calculation in clinical practice.

RESULTS

62 out of 10133 patients (0.61%) had a severe perineal tear. Univariate analysis identified gestational age >40 weeks, nulliparity, moderate/severe obesity, oxytocin use in pushing stage, sinciput presentation, instrumental delivery, shoulder dystocia, pushing stage ≥90 min, lithotomy position, birth weight >4 kg, head circumference at birth >34 cm and length at birth >50 cm as risk factors. Multivariate analysis identify moderate/severe obesity (OR = 2.8), instrumental delivery (OR = 2.6) and birth weight (OR = 1.1/hg) as independent risk factors. Using the predicted risk score from the final model (bootstrap-validated AUC 70%), we designed a nomogram for severe perineal tears absolute risk calculation.

CONCLUSION

Moderate/severe obesity, instrumental delivery and foetal weight resulted as independent risk factors for severe obstetrical tears.

Risk factors for obstetric anal sphincter injuries (OASI) at a tertiary centre in south India

INTRODUCTION AND HYPOTHESIS

Despite several studies that have reported risk factors for obstetric anal sphincter injuries (OASI), data from the Indian subcontinent are scarce. The purpose of this study was to identify risk factors for these sphincter injuries in an Indian population.

METHODS

This was a case-control study within a retrospective cohort of vaginal deliveries at a tertiary care facility. All vaginal births beyond 24 completed weeks of gestation and birth weight ≥500 g from January 2008 to December 2012 were identified from the hospital electronic database. Cases were women with OASI sustained during vaginal delivery; the rest constituted controls. Potential risk factors for occurrence and severity of OASI were assessed initially using bivariate analysis and then a logistic regression model.

RESULTS

The incidence of sphincter injury was 2.1% of vaginal births and 1.1% of all deliveries, and major-degree (3c and 4th-degree) tears constituted 20.9% of tears. After adjusted analysis, significant predictors for injury included primiparity, delivery at or beyond 41 weeks of gestation, epidural analgesia, instrumental delivery, shoulder dystocia, birth weight ≥4000 g, and head circumference ≥35 cm. Episiotomy protected against sphincter injuries, particularly in forceps and ventouse deliveries. Shoulder dystocia was significantly associated with major-degree tears, while episiotomy appeared to be protective.

CONCLUSION

Risk factors are similar to those in other population groups; however, primiparity appears to be associated with lesser risk and forceps delivery with greater risk of sphincter trauma than previously reported.

Cell-based secondary prevention of childbirth-induced pelvic floor trauma

With advancing population age, pelvic-floor dysfunction (PFD) will affect an increasing number of women. Many of these women wish to maintain active lifestyles, indicating an urgent need for effective strategies to treat or, preferably, prevent the occurrence of PFD. Childbirth and pregnancy have both long been recognized as crucial contributing factors in the pathophysiology of PFD. Vaginal delivery of a child is a serious traumatic event, causing anatomical and functional changes in the pelvic floor. Similar changes to those experienced during childbirth can be found in symptomatic women, often many years after delivery. Thus, women with such PFD symptoms might have incompletely recovered from the trauma caused by vaginal delivery. This hypothesis creates the possibility that preventive measures can be initiated around the time of delivery. Secondary prevention has been shown to be beneficial in patients with many other chronic conditions. The current general consensus is that clinicians should aim to minimize the extent of damage during delivery, and aim to optimize healing processes after delivery, therefore preventing later dysfunction. A substantial amount of research investigating the potential of stem-cell injections as a therapeutic strategy for achieving this purpose is currently ongoing. Data from small animal models have demonstrated positive effects of mesenchymal stem-cell injections on the healing process following simulated vaginal birth injury.

Midwives' Management during the Second Stage of Labor in Relation to Second-Degree Tears-An Experimental Study

INTRODUCTION

Most women who give birth for the first time experience some form of perineal trauma. Second-degree tears contribute to long-term consequences for women and are a risk factor for occult anal sphincter injuries. The objective of this study was to evaluate a multifaceted midwifery intervention designed to reduce second-degree tears among primiparous women.

METHODS

An experimental cohort study where a multifaceted intervention consisting of 1) spontaneous pushing, 2) all birth positions with flexibility in the sacro-iliac joints, and 3) a two-step head-to-body delivery was compared with standard care. Crude and Adjusted OR (95% CI) were calculated between the intervention and the standard care group, for the various explanatory variables.

RESULTS

A total of 597 primiparous women participated in the study, 296 in the intervention group and 301 in the standard care group. The prevalence of second-degree tears was lower in the intervention group: [Adj. OR 0.53 (95% CI 0.33-0.84)]. A low prevalence of episiotomy was found in both groups (1.7 and 3.0%). The prevalence of epidural analgesia was 61.1 percent. Despite the high use of epidural analgesia, the midwives in the intervention group managed to use the intervention.

CONCLUSION

It is possible to reduce second-degree tears among primiparous women with the use of a multifaceted midwifery intervention without increasing the prevalence of episiotomy. Furthermore, the intervention is possible to employ in larger maternity wards with midwives caring for women with both low- and high-risk pregnancies.

Obstetrical Anal Sphincter Injuries: Does Obstetrical Care Provider Matter? A Quality Assurance Study in Ontario

OBJECTIVES

We sought to determine the rates of obstetrical anal sphincter tears (OASIS) between types of obstetrical care providers at Kingston General Hospital (KGH) and in Ontario via the Better Outcomes Registry Network (BORN).

METHODS

This cross-sectional study collected patient, demographic, and delivery data from all vaginal deliveries at KGH from June 2011 to June 2014 and all vaginal deliveries through the BORN database from June 2012 to June 2014.

RESULTS

During this period, 4.6% and 3.5% of all vaginal deliveries at KGH and in Ontario, respectively, were complicated by OASIS. The OASIS' rates were not statistically different between admitting care providers at KGH: 4.9%, 3.8%, and 3.7% of vaginal deliveries by obstetricians, family physicians, and midwives, respectively, in contrast to a higher rate of OASIS in women admitted under midwifery care in the province-wide data: 3.4%, 3.2%, and 4.4% for obstetricians, family physicians, and midwives, respectively. The rate of OASIS in patients who had an intrapartum transfer of care (TOC) from a family physician or midwife to an obstetrician was 13.8% at KGH, and 13.6% as reported by BORN, significantly higher than 3.8% (KGH) or 2.9% (BORN) in those who remained under the family physician, or midwife. The relative risk of OASIS in women transferred to an obstetrician compared to those who were admitted and delivered by an obstetrician was 3.9 (95% confidence interval, 3.6-4.3, P < 0.0001).

CONCLUSIONS

Only when an intrapartum TOC is needed does the OASIS rate substantially increase, reflecting the underlying indication for TOC is leading to more intervention associated with risk of OASIS.

An obstetric sphincter injury risk identification system (OSIRIS): is this a clinically useful tool?

Introduction and hypothesis

To establish the contribution of maternal, fetal and intrapartum factors to the risk of incidence of obstetric anal sphincter injuries (OASIS) and assess the feasibility of an OASIS risk prediction model based on variables available to clinicians prior to birth.

Methods

This was a population-based, retrospective cohort study using single-site data from the birth database of Aarhus University Hospital, Denmark. The participants were all women who had a singleton vaginal birth during the period 1989 to 2006. Univariate and multivariate logistic regression analyses were performed using multiple imputations for missing data and internally validated using bootstrap methods. The main outcome measures were the contributions of maternal, fetal and intrapartum events to the incidence of OASIS.

Results

A total of 71,469 women met the inclusion criteria, of whom 1,754 (2.45 %) sustained OASIS. In the multivariate analysis of variables known prior to birth, maternal age 20 – 30 years (OR 1.65, 95 % CI 1.44 – 1.89) and ≥30 years (OR 1.60, 95 % CI 1.39 – 1.85), occipitoposterior fetal position (OR 1.34, 95 % CI 1.06 – 1.70), induction/augmentation of labour (OR 1.46, 95 % CI 1.32 – 1.62), and suspected macrosomia (OR 2.20, 95 % CI 1.97 – 2.45) were independent significant predictors of OASIS, with increasing parity conferring a significant protective effect. The ‘prebirth variable’ model showed a 95 % sensitivity and a 24 % specificity in predicting OASIS with 1 % probability, and a 3 % sensitivity and a 99 % specificity in predicting OASIS with a 10 % probability.

Conclusions

Our model identified several significant OASIS risk factors that are known prior to actual birth. The prognostic model shows potential for ruling out OASIS (high sensitivity with a low risk cut-off value), but is not useful for ruling in the event.

Electronic supplementary material

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Predicting obstetric anal sphincter injuries in a modern obstetric population

BACKGROUND

Perineal lacerations are common at the time of vaginal delivery and may predispose patients to long-term pelvic floor disorders, such as urinary incontinence and pelvic organ prolapse. Obstetric anal sphincter injuries, which are the most severe form of perineal lacerations, result in disruption of the anal sphincter and, in some cases, the rectal mucosa during vaginal delivery. Long-term morbidity, including pain, pelvic floor disorders, fecal incontinence, and predisposition to recurrent injury at subsequent delivery may result. Despite several studies that have reported risk factors for obstetric anal sphincter injuries, no accurate risk prediction models have been developed.

OBJECTIVE

The purpose of this study was to identify risk factors and develop prediction models for perineal lacerations and obstetric anal sphincter injuries.

STUDY DESIGN

This was a nested case control study within a retrospective cohort of consecutive term vaginal deliveries at 1 tertiary care facility from 2004-2008. Cases were patients with any perineal laceration that had been sustained during vaginal delivery; control subjects had no lacerations of any severity. Secondary analyses investigated obstetric anal sphincter injury (3rd- to 4(th)-degree laceration) vs no obstetric anal sphincter injury (0 to 2(nd)-degree laceration). Baseline characteristics were compared between groups with the use of the chi-square and Student t test. Adjusted odds ratios and 95% confidence intervals were calculated with the use of multivariable logistic regression. Prediction models were created and model performance was estimated with receiver-operator characteristic curve analysis. Receiver-operator characteristic curves were validated internally with the use of the bootstrap method to correct for bias within the model.

RESULTS

Of the 5569 term vaginal deliveries that were recorded during the study period, complete laceration data were available in 5524 deliveries. There were 3382 perineal lacerations and 249 (4.5%) obstetric anal sphincter injuries. After adjusted analysis, significant predictors for laceration included nulliparity, non-black race, longer second stage, nonsmoking status, higher infant birthweight, and operative delivery. Private health insurance, labor induction, pushing duration, and regional anesthesia were not statistically significant in adjusted analyses. Significant risk factors for obstetric anal sphincter injury were similar to predictors for any laceration; nulliparity and operative vaginal delivery had the highest predictive value. Area under the curve for the predictive ability of the models was 0.70 for overall perineal laceration, and 0.83 for obstetric anal sphincter injury. When limited to primiparous patients, 1996 term vaginal deliveries were recorded. One hundred ninety-two women sustained an obstetric anal sphincter injury; 1796 women did not. After adjusted analysis, significant predictors for laceration included non-black race, age, obesity, and nonsmoking status. In secondary analyses, significant predictors for obstetric anal sphincter injury included non-black race, nonsmoking status, longer duration of pushing, operative vaginal delivery, and infant birthweight. Area under the curve for the predictive ability of the models was 0.60 for any laceration and 0.77 for obstetric anal sphincter injury.

CONCLUSIONS

Significant risk factors for sustaining any laceration and obstetric anal sphincter injury during vaginal deliveries were identified. These results will help identify clinically at-risk patients and assist providers in counseling patients about modifications to decrease these risks.

Perineal injuries and birth positions among 2992 women with a low risk pregnancy who opted for a homebirth

BACKGROUND

Whether certain birth positions are associated with perineal injuries and severe perineal trauma (SPT) is still unclear. The objective of this study was to describe the prevalence of perineal injuries of different severity in a low-risk population of women who planned to give birth at home and to compare the prevalence of perineal injuries, SPT and episiotomy in different birth positions in four Nordic countries.

METHODS

A population-based prospective cohort study of planned home births in four Nordic countries. To assess medical outcomes a questionnaire completed after birth by the attending midwife was used. Descriptive statistics, bivariate analysis and logistic regression were used to analyze the data.

RESULTS

Two thousand nine hundred ninety-two women with planned home births, who birthed spontaneously at home or after transfer to hospital, between 2008 and 2013 were included. The prevalence of SPT was 0.7 % and the prevalence of episiotomy was 1.0 %. There were differences between the countries regarding all maternal characteristics. No association between flexible sacrum positions and sutured perineal injuries was found (OR 1.02; 95 % CI 0.86-1.21) or SPT (OR 0.68; CI 95 % 0.26-1.79). Flexible sacrum positions were associated with fewer episiotomies (OR 0.20; CI 95 % 0.10-0.54).

CONCLUSION

A low prevalence of SPT and episiotomy was found among women opting for a home birth in four Nordic countries. Women used a variety of birth positions and a majority gave birth in flexible sacrum positions. No associations were found between flexible sacrum positions and SPT. Flexible sacrum positions were associated with fewer episiotomies.

Urgent EMS managed out-of-hospital delivery dispatches in Helsinki

BACKGROUND

The aim of this study was to examine Helsinki Emergency Medical Services (EMS) and hospital records to determine the incidence and possible complications of out-of-hospital deliveries managed by EMS in Helsinki.

METHODS

We retrospectively analysed all urgent ambulance dispatches relating to childbirth in Helsinki from January 1, 2010 to December 31, 2014 with further analysis of hospital records for the out-of-hospital deliveries. Patients were divided in to two groups: those who delivered before reaching hospital and those who did not deliver before reaching hospital and differences between groups were analysed. Deliveries with gestational age of at least 22 + 0 weeks were considered as births in statistical analysis as this is the current national practice.

RESULTS

There were 799 urgent dispatches during the study period. In 102 (12.8 %) of these delivery took place before reaching the hospital. The incidence of EMS managed out-of-hospital delivery was found to be 3.0/1000 births. The annual number of out-of-hospital deliveries attended by EMS increased from 15 in 2010 to 28 in 2014. No stillbirths were reported. Neither maternal or perinatal deaths nor major maternal complications were noted in the study population.

DISCUSSION

Out-of-hospital deliveries represent a small minority of EMS calls and remain a challenge to maintaining professional capabilities. Small sample size might have limited the ability of the study to pick up rare complications.

CONCLUSIONS

The amount of out-of-hospital deliveries in Helsinki increased during the five-year study period. There were no maternal or perinatal mortality or major complications resulting in long-term sequelae associated with the EMS-managed out-of-hospital births.

Obstetrical Anal Sphincter Injuries (OASIS): Prevention, Recognition, and Repair

OBJECTIVE

To review the evidence relating to obstetrical anal sphincter injuries (OASIS) with respect to diagnosis, repair techniques and outcomes. To formulate recommendations as to patient counselling regarding route of delivery for subsequent pregnancy after OASIS.

OPTIONS

Obstetrical care providers caring for women with OASIS have the option of repairing the anal sphincter using end-to-end or overlapping techniques. They may also be involved in counselling women with prior OASIS regarding the route of delivery for future pregnancies.

OUTCOMES

The outcome measured is anal continence following primary OASIS repair and after subsequent childbirth.

EVIDENCE

Published literature was retrieved through searches of Medline, EMBASE, and The Cochrane Library in May 2011 using appropriate controlled vocabulary (e.g., anal canal, obstetrics, obstetric labour complication, pregnancy complication, treatment outcome, surgery, quality of life) and key words (obstetrical anal sphincter injur*, anus sphincter, anus injury, delivery, obstetrical care, surgery, suturing method, overlap, end-to-end, feces incontinence). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to September 2014. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Benefits from implementation of these guidelines include: improved diagnosis of OASIS, optimal functional outcomes following repair, and evidence-based counselling of women for future childbirth.

Mode of delivery after obstetric anal sphincter injury

OBJECTIVE

To assess the effect of vaginal delivery and caesarean section on faecal symptoms and structure and function of anal sphincter in women who sustained obstetric anal sphincter injuries (OASIS) in their previous pregnancy and were advised about the mode of delivery based on faecal incontinence symptoms, anal manometry and endoanal ultrasound.

STUDY DESIGN

It is a descriptive study on a cohort of women who had OASIS from 2006 to 2013. They were assessed after OASIS and during subsequent pregnancy with a questionnaire, endoanal ultrasound and anal manometry. Vaginal delivery was recommended to asymptomatic women with normal investigations. Elective caesarean section was recommended to women with faecal symptoms, anal sphincter defects of more than 30° or low resting or incremental anal pressures. All women were reassessed after subsequent delivery.

RESULTS

Fifty women who had pregnancies after OASIS, were seen after OASIS, during subsequent pregnancy and after the second delivery. 15 women had faecal symptoms after OASIS. The external, internal and combined anal sphincter defects were seen in 13, 11 and 9 women respectively. Low resting and incremental pressure were seen in 15 and 11 women respectively. Caesarean section was done in 22 women and 28 women delivered vaginally. Worsening of faecal symptoms and reduction in anal pressures were not observed in planned vaginal delivery or elective caesarean section groups. Faecal symptoms were worse with reduced anal pressures in three women from the planned caesarean section group. One of the women had a vaginal delivery and two women had emergency caesarean section at 7cm and 10cm dilatation. There were no new sphincter defects or recurrent OASIS in any of the women in the study group.

CONCLUSION

Decision about the mode of delivery of pregnancy after OASIS based on symptoms, anal manometry and endoanal ultrasound helps in preserving the anal sphincter function and avoiding unnecessary caesarean sections. Further follow-up of these patients is essential to evaluate the long-term effects of this decision.