Assessment of Perineal Scars on Translabial Pelvic Floor Ultrasound: A Pilot Study.

OBJECTIVE: We aimed to describe a method for identifying and evaluating perineal scars using translabial pelvic floor ultrasound. We hypothesized that translabial ultrasound can identify a perineal scar and can differentiate episiotomies from spontaneous tears. METHODS: This pilot study is a secondary analysis of data obtained in the Epi-No® trial. Perineal integrity was assessed using volumes acquired on pelvic floor muscle contraction according to the method previously described for anal sphincter imaging. A scar was diagnosed if a hypoechoic distortion in the perineum was noted. We postulated that an episiotomy would result in a linear scar visible on four dimensional translabial ultrasound whereas nonlinear scars were considered the result of spontaneous perineal tear of grade 2 or higher. The results of this assessment were compared with data retrieved from electronic medical records. RESULTS: A scar was identified in 79/120 women (66%): 42 (35%) linear and 37 (31%) nonlinear. Sonographic and clinical diagnosis agreed on the presence or absence of perineal trauma in 66%. Agreement for the type of laceration was 50%. CONCLUSION: In this retrospective pilot study, a blinded assessment of translabial ultrasound volume data showed agreement between clinical data and sonographic assessment of perineal integrity in 66% and of type of laceration in 50%. More work is needed to optimize the method in assessment of perineal scars to improve its performance before it can be used in clinical audit and research.

Obstetric risk factors for anal sphincter trauma in a urogynecological population.

INTRODUCTION AND HYPOTHESIS: Obstetric anal sphincter tears are the single major modifiable risk factor for anal incontinence (AI) in women. We undertook a retrospective observational study in a tertiary urogynecology unit to describe the prevalence of sonographic anal sphincter defects in a urogynecological population and investigate obstetric risk factors. METHODS: Files of women seen for investigation of pelvic floor disorders between January 2014 and May 2021 were reviewed. Sonographic defects of the external anal sphincter were analyzed using stored 4D ultrasound imaging data. Explanatory parameters were number of vaginal births, delivery mode, age at first vaginal birth, and birthweight of the first vaginally born baby. RESULTS: Of 3,037 women seen during the inclusion period, data were missing in 219, leaving 2,818. AI was reported by 508 (18%), with a mean St Marks score of 11 (1-23) and a mean bother score of 5.9 (0-10). External sphincter defects were detected in 945 women (34%), with a "residual defect" in 343 (12%). The strongest risk factors for a residual defect were first vaginal birth and forceps, with higher-order multiparity adding risk. On multivariate analysis, forceps and vaginal parity >5 remained significant predictors, as opposed to age at first birth and birthweight of the firstborn. CONCLUSIONS: In this observational study in urogynecological patients, 12% showed a residual EAS defect on imaging. The most obvious risk factors for the diagnosis of a residual defect on exo-anal imaging were the first vaginal birth and forceps, with higher-order vaginal parity conveying additional risk.

Is urethral pressure associated with parity and delivery mode?

INTRODUCTION AND HYPOTHESIS: Stress urinary incontinence is the most prevalent type of urinary incontinence and childbirth is a risk factor. The aim of this study is to evaluate the association between delivery mode and urethral sphincter function as measured by the maximum urethral pressure (MUP). METHODS: A retrospective study on women seen in a tertiary urogynaecological center for urodynamic testing between January 2017 to December 2019. Women were classified into the following groups: (1) nulliparous; (2) caesarean section only; (3) at least one spontaneous vaginal delivery but no instrumental deliveries; (4) at least one vacuum delivery but no forceps; (5) at least one forceps delivery. RESULTS: The complete data sets of 1238 women were analysed; 1112 (90%) were vaginally parous. Mean age was 58 (18-95) years. Mean parity was 2.6 (0-9); 57 (4.6%) were nulliparous, 69 (5.6%) had only been delivered by caesarean section, 762 (61.6%) had at least one spontaneous vaginal delivery but no instrumental deliveries, 41 (3.3%) had at least one vacuum but no forceps delivery, and 309 (25%) had at least one forceps delivery. Mean MUP was 41.8 cmH2O. There was a significant association between vaginal parity and MUP (P < 0.001). On ANOVA test, delivery mode was significantly associated with MUP. This became nonsignificant on regression analysis, with only age significantly associated with MUP (P < 0.001). CONCLUSIONS: The effect of childbirth on urethral sphincter function seems to be largely due to the first vaginal birth. We failed to show an effect of instrumental delivery.

Imaging Characteristics of Episiotomy Scars on Translabial Ultrasound: An Observational Study.

INTRODUCTION: Episiotomy has been purported to protect the anal sphincter from injury; efficacy is, however, disputed. Correct execution of episiotomy may have substantial implications. We aimed to describe the characteristics of episiotomy scars on translabial ultrasound (TLUS). METHODS: In this retrospective observational study involving women after repair of obstetric anal sphincter injuries, 76 women with a history of episiotomy were analyzed. Episiotomy scars were assessed on tomographic ultrasound in the transverse plane using volumes acquired on pelvic floor muscle contraction. We measured scar length, depth, and angle relative to a vertical reference line. Episiotomy scars were described as 1) ipsilateral if they started on the same side as the direction of the episiotomy, 2) contralateral if on the opposite side, and 3) mediolateral if the scar began in the midline. RESULTS: The mean scar angle was 50.5° (SD 14°; range 14.4°-79.3°) while mean scar length was 14.2 mm (SD 4.5; range 5.7-27.5 mm) and depth was 8.4 mm (SD 2.8, range 3.1-18.2 mm). Sixteen (21%) scars were located mediolateral while 32 (42%) were ipsilateral. In 28 (37%) women, the starting point of the episiotomy was located contralateral to the direction of the episiotomy. CONCLUSION: In this pilot series, the mean angle of episiotomy scars was within the safe zone of 40° to 60°, however, in one-third of cases the cut may have been initially directed toward the sphincter, not away from it. This observation suggests that not all episiotomies are performed optimally.

Is the Visual Analogue Scale inferior to the Pelvic Organ Prolapse Distress Inventory for assessing symptom bother of pelvic organ prolapse?

AIMS: Disease-specific validated questionnaires are used to quantify symptom severity, but they are time consuming to complete and evaluate. A Visual Analogue Scale (VAS) assessment of bother is simpler and faster. The aim of this study is to compare VAS with individual and composite pelvic floor disability index-short form 20 items in predicting significant pelvic organ prolapse (POP). METHODS: A retrospective analysis of data was obtained at a tertiary urogynaecological clinic between February 2017 and August 2018. All women filled out the PFDI-20 and underwent a standardised physician-directed interview, POP-Q and translabial ultrasound. Women with symptoms of POP were asked to indicate the degree of bother using a VAS. Receiver operating characteristic curves were used to evaluate the performance of individual Pelvic Organ Prolapse Distress Inventory (POPDI)-6 items, the six-item composite POPDI-6 score, and VAS in predicting significant POP on clinical and ultrasound examination. RESULTS: The complete data sets of 231 women were analysed. Median VAS for POP was 2.9 (range 0-10). Median POPDI-6 individual and composite scores for items one to six were 2, 2, 2, 1, 2, 0 (all range 0-4) and 9 (range 0-22), respectively. The majority had significant prolapse on clinical examination (n = 195, 84%) and on ultrasound (n = 192, 83%). The composite POPDI-6 prolapse score provided areas under the curve of 0.68 and 0.64 for the prediction of clinical and sonographic POP, compared to 0.74 and 0.69, respectively, for VAS. The difference was not significant (P = 0.3 and 0.8, respectively). CONCLUSIONS: The VAS score was not inferior to the POPDI-6 in predicting significant POP. It has the potential to simplify the assessment of symptom severity.

International Urogynecological Consultation: clinical definition of pelvic organ prolapse.

INTRODUCTION AND HYPOTHESIS: This segment of Chapter 1 of the International Urogynecology Consultation (IUC) on pelvic organ prolapse (POP) reviews the literature on the clinical definition of POP with the intent of creating standard terminology. METHODS: An international group containing nine urogynecologists and one university-based medical librarian performed a search of the literature using pre-specified search terms in PubMed, Embase, and Scopus. Publications were eliminated if not relevant to the clinical definition of POP, and those articles remaining were evaluated for quality using the Specialist Unit for Review Evidence (SURE). The resulting list of articles was used to inform a comprehensive review and creation of the clinical definition of POP. RESULTS: The original search yielded 31,931 references, of which 167 were used by the writing group. Ultimately, 78 are referenced in the manuscript. CONCLUSIONS: The clinical definition of POP for this review of the literature is: "anatomical prolapse with descent of at least one of the vaginal walls to or beyond the vaginal hymen with maximal Valsalva effort WITH the presence either of bothersome characteristic symptoms, most commonly the sensation of vaginal bulge, or of functional or medical compromise due to prolapse without symptom bother."

Does pregnancy affect pelvic floor functional anatomy? A retrospective study.

OBJECTIVE: Vaginal childbirth is an established main aetiological factor in the pathogenesis of female pelvic floor dysfunction. However, pregnancy itself is also likely to have an effect. This study investigated the effect of pregnancy on pelvic floor functional anatomy. STUDY DESIGN: This was a retrospective observational study involving vaginally nulliparous women who presented to a tertiary urogynaecology unit with symptoms and signs of pelvic floor dysfunction between 2006 and 2014. Nulliparous women were compared with those who delivered exclusively by Caesarean Section (CS). All had undergone a standardised clinical interview, ICS POP-Q assessment and 3D/4D translabial pelvic floor ultrasound. Main outcome measures included sonographically determined pelvic organ position and hiatal dimensions on Valsalva and pelvic floor muscle contraction (PFMC). RESULTS: Of 2930 women seen during the study period, 242 had never given birth vaginally. One hundred and twenty-nine (53 %) were nulliparous, and 113 (47 %) were delivered by CS only. The CS group demonstrated significantly higher pelvic organ mobility in the anterior compartment (all P < 0.05) and a larger hiatal area on Valsalva (P = 0.004). All sonographic measures of pelvic floor muscle function demonstrated greater tissue displacement on PFMC in the CS group (all P < 0.05). CONCLUSIONS: Compared to nulliparas, women who delivered exclusively by CS showed increased pelvic organ descent on Valsalva and tissue displacement on PFMC, implying increased tissue elasticity/ compliance or reduced stiffness, consistent with a small permanent hormonal and/or mechanical effect of pregnancy.

'Normal birth': Time to change our tune?

Recent research indicates that atraumatic 'normal vaginal birth' only occurs in 33-40% of women who intend to achieve a vaginal delivery, depending on how the term 'normal birth' is defined. In contrast, the NSW birth policy continues to promote 'normal birth', suggesting that the majority of women will achieve 'normal birth' and that 'normal birth' produces optimal maternal outcomes. Our continued use of the term 'normal birth' may be outdated. This article will consider the term 'normal birth' with regard to history, politics, policy and obstetric practice, and recommend a reconsideration of terminology.

Persistent levator co-activation is not associated with symptoms or bother of obstructed defecation.

INTRODUCTION AND HYPOTHESIS: The objective was to determine whether levator contraction during Valsalva (i.e. levator co-activation), as visualised on four-dimensional translabial ultrasound (4D-TLUS), is associated with obstructed defecation (OD). METHODS: This was a retrospective study including patients attending a tertiary urogynecological unit. All underwent an interview, clinical examination and 4D-TLUS. Frequent straining at stool, digitation or sensation of incomplete emptying during defecation were considered symptoms of OD. Archived 4D-TLUS volumes were evaluated, blinded to all other data. Hiatal anteroposterior (AP) diameter (cm) and hiatal area (cm2) were measured at rest and on maximal Valsalva. Patients with anatomical explanations for OD (rectocele, enterocele and/or rectal intussusception) were excluded. Reduction of hiatal AP diameter and hiatal area on Valsalva were tested for association with symptoms of OD. RESULTS: Overall, 1,383 women attended the unit from May 2013 to July 2016. Seven hundred and eight were excluded because of rectocele (n = 645), enterocele (n = 116) or rectal intussusception (n = 41) and 10 owing to missing data, leaving 665. Mean age was 53 years (16-89), mean body mass index (BMI) 27.3 kg/m2 (15.7-64.4). OD symptoms were reported by 368 (55.3%) patients. On imaging, a reduction in hiatal AP diameter on Valsalva was seen in 11.7% cases (78 out of 665) with a mean reduction of 3.5 mm (0.2-17). A mean reduction in hiatal area of 1.9cm2 (0.03-14.8) on Valsalva was seen in 9.8% cases (65 out of 665). These sonographic measures of levator co-activation were not associated with OD symptoms or bother caused by them (p > 0.05). CONCLUSIONS: Levator co-activation seen on TLUS is not associated with obstructed defecation.

Is vaginal flatus related to pelvic floor functional anatomy?

INTRODUCTION AND HYPOTHESIS: Vaginal flatus is an embarrassing condition that can impair women's quality of life. The underlying pathophysiology is unclear. We aimed to evaluate the association between vaginal flatus and pelvic floor anatomy. METHODS: Retrospective observational study on women seen in a tertiary urogynaecological service. All had undergone a standardised interview, clinical examination and four-dimensional transperineal ultrasound. Offline analysis of volume data was performed blinded against clinical data. RESULTS: Datasets of 570 women were analysed. Five hundred twelve (90%) were vaginally parous. Vaginal flatus was reported by 190 (33%). Mean bother score was 4.2 (SD 3.4, range 0-10). One hundred eighty-five reported frequency of vaginal flatus: it occurred < once a month in 25 (14%), once a month in 70 (38%), once a week in 47 (25%), once daily in 28 (15%) and > once daily in 15 (8%). One hundred two women identified the following precipitating factors: intercourse in 72 (71%), postural change in 22 (22%) and physical activities in 9 (9%). Vaginal birth, central and posterior compartment prolapse, anal incontinence, higher levator resting tone and younger age were associated with vaginal flatus. The latter was moderately correlated with symptom bother (correlation coefficient - 0.21). CONCLUSIONS: Vaginal flatus is a prevalent and bothersome condition affecting one-third of our study population. The condition is associated with pelvic floor functional anatomy. A higher resting tone may confer a higher resistance against which trapped air is expelled during physical activities. Younger age was moderately correlated with symptom bother.

Parity and anal sphincter trauma.

INTRODUCTION AND HYPOTHESIS: Obstetric anal sphincter injury (OASI) is a form of maternal trauma secondary to vaginal birth. Women with a history of OASI are deemed to be at a higher risk of recurrence. However, it is unclear if multiparity is associated with higher prevalence. The aim of the study was to test the following hypothesis: the prevalence of external anal sphincter (EAS) tears diagnosed on transperineal ultrasound (TPUS) is related to vaginal parity. METHODS: A retrospective observational study on 1,273 women who attended a tertiary urogynecology service between January 2014 and December 2016. Patients had undergone a standardized interview, clinical examination and 4D TPUS. Tomographic ultrasound imaging was used to evaluate the EAS, blinded to all clinical data. RESULTS: Of 1,273 women, 1,143 (90%) were vaginally parous, with a mean vaginal parity of 2 (range 1-8). Mean age was 54 (range 17-89) years. Anal incontinence was reported in 186 women (15%) with an average St Mark's incontinence score of 12 (range 1-23). EAS defects on ultrasound were identified in 148 (12%). On univariate analysis, there was no significant difference in the prevalence of EAS defects in vaginally primiparous and multiparous women (p = 0.460). CONCLUSIONS: There is no significant difference in the prevalence of EAS tears between vaginally primiparous and multiparous women. This argues against additional traumatic effects of subsequent vaginal births.

A pilot study on surgical reduction of the levator hiatus-the puborectalis sling.

INTRODUCTION AND HYPOTHESIS: Female pelvic organ prolapse recurrence has been shown to be associated with levator hiatal distensibility. Reducing hiatal size surgically may reduce recurrence risk. This study aims to demonstrate a novel surgical procedure, the puborectalis sling (PR sling), designed to reduce the levator hiatal area, and to assess the medium-term safety and efficacy of this procedure. METHODS: One hundred fifteen women undergoing prolapse repair with a pre-operative hiatal area on Valsalva of ≥ 35 cm2 were recruited into this phase 1 prospective multicentre pilot study. All underwent a PR sling procedure after completion of standard repairs. Primary outcome was levator hiatal area measured on ultrasound. RESULTS: One hundred ten patients were evaluated at least 3 months post-operatively. At 2.5 years average follow-up, there was an average of 12 cm2 (range 6-16 cm2) reduction in hiatal area from a mean pre-operative hiatal area of 43.9 (35-63) cm2. Thirty per cent (28/93) were symptomatic of prolapse, 66% (61/93) had clinical prolapse recurrence whilst 49% (46/93) had sonographic recurrence. Three patients required a return to theatre; one case of infection resulted in mesh removal, one had severe obstructed defecation requiring sling loosening and another had buttock pain with faecal impaction that resolved after manual disimpaction. There were no long-term sequelae. CONCLUSIONS: The levator hiatal area can be reduced surgically, with almost 30% reduction in area seen in this pilot study. The reduction was significant and sustained up to 2 years with no major long-term complications.

Definition of apical descent in women with and without previous hysterectomy: A retrospective analysis.

BACKGROUND: While normal pelvic organ support has been defined for women with intact uterus, this is not the case for post- hysterectomy vault descent. A recent systematic review found that definitions of apical prolapse are highly variable. OBJECTIVES: To investigate the relationship between prolapse symptoms and apical POP-Q measurements and establish cutoffs for 'significant apical descent using receiver-operator characteristics (ROC) statistics. STUDY DESIGN: Retrospective analysis of patients seen at a tertiary urogynecological unit. Evaluation included a standardized interview and clinical assessment using the Pelvic Organ Prolapse Quantification (POP-Q) system. ROC curves were prepared for the relationship between prolapse symptoms and POP-Q measure "C". RESULTS: The records of 3010 women were available for analysis. Prolapse symptoms were reported by 52.3% (n = 1573), with a mean bother of 5.9 (SD 3.0, range 0-10). POP-Q point "C" was associated with symptoms of prolapse (p <0.0001) and prolapse bother (p <0.0001) on both univariate and multivariate analysis. ROC curves for women with and without uterus were similar, although the relationship between apical descent and symptoms of prolapse was stronger for women with uterus (AUC 0.728 versus 0.678). After controlling for multi-compartment prolapse, the models improved, resulting in AUCs of 0.782 and 0.720. For prediction of prolapse symptoms, cutoffs were set at C = -5 (sensitivity 0.73, specificity 0.67 with uterus in situ, sensitivity 0.59, specificity, 0.73 after hysterectomy). CONCLUSION: A cut- off for 'significant central compartment descent' of 5 cm above the hymen on Valsalva seems valid regardless of previous hysterectomy.

How Valid Is Tomographic Ultrasound Imaging in Diagnosing Levator and Anal Sphincter Trauma?

OBJECTIVES: Three-/four-dimensional translabial ultrasound (US) is increasingly used to image the levator ani and anal sphincters, especially in the form of tomographic US. The aim of the study was to evaluate the validity of these published methods. METHODS: This work was a retrospective analysis of datasets of 172 nulliparous women who attended 2 tertiary urogynecologic centers for symptoms of pelvic floor dysfunction between June 2012 and September 2016. All patients had a standardized interview, clinical examination, and 4-dimensional translabial US examination. An evaluation of volume data was performed by the first author, who was blinded against all clinical data, including parity. An assessment for levator avulsion and anal sphincter defects was performed using stored US volume data. RESULTS: Data sets of 162 and 153 nulliparous women were available for levator and anal sphincter assessments, respectively. On the assessment by the first author, a complete avulsion was diagnosed in 3 nulliparas. On a review by 2 senior authors, 1 was judged as positive and the other 2 as normal. On the sphincter assessment, 2 significant external anal sphincter defects were detected. On the review, 1 was judged as false-positive. The second was judged as highly abnormal by all authors. Therefore, 1 nullipara each was diagnosed with avulsion and a significant external anal sphincter defect. CONCLUSIONS: Published diagnostic criteria for levator avulsion and external anal sphincter trauma on tomographic US imaging are highly unlikely to result in false-positive findings. This finding supports the clinical validity of this method.

Total vaginal length: Does it matter for assessing uterine prolapse?

INTRODUCTION AND HYPOTHESIS: Using the International Continence Society Pelvic Organ Prolapse Quantification (ICS POP-Q) system, uterine prolapse staging requires measurement of total vaginal length (TVL). The aim of this study was to determine whether TVT is a confounder of the relationship between uterine descent and POP symptoms. METHODS: This is a retrospective study on 721 patients seen in a tertiary urogynaecological unit. All patients had undergone a standardised, in-house, physician-led questionnaire and digital POP-Q examination. Patients with a history of hysterectomy or with a dominant prolapse in the anterior ± posterior compartment were excluded from analysis, leaving 393 complete data sets for analysis. Association between prolapse symptoms (lump/drag) and station of cervix (i.e. C) were tested. Age, body mass index (BMI), menospausal status and vaginal parity were tested as potential confounders. Variables that were significant on binary logistic regression (P < 0.05) were included in a model for receiver operting characteristic (ROC) statistical analysis. This was repeated after adding TVL to the model. Likelihood ratio test was performed to compare models. RESULTS: On binary logistic regression, prolapse symptoms were significantly associated with C, menopausal status and TVL (all P < 0.03). ROC analysis yielded an area under the curve (AUC) of 0.75 with menopausal status and C in the model. Adding TVL yielded an AUC of 0.773. The difference is statistically significant on the likelihood ratio test (P < 0.001). CONCLUSIONS: Adding TVL improved the performance of cervical station in predicting prolapse symptoms, validating the practice of using TVL in staging uterine prolapse.

Medium- to Long-term Follow-up of Obstetric Anal Sphincter Injury.

BACKGROUND: Obstetric anal sphincter injury is the primary modifiable risk factor for anal incontinence in women. Currently, endoanal ultrasound is most commonly used to detect residual anal sphincter defects after childbirth. Translabial ultrasound has recently been introduced as a noninvasive alternative. OBJECTIVES: This study aimed to determine medium- to long-term outcomes in women after obstetric anal sphincter injuries diagnosed and repaired at delivery. DESIGN: This is a cross-sectional study. SETTINGS: This study was performed in a tertiary obstetric unit. PATIENTS: Between 2005 and 2015, 707 women were diagnosed with obstetric anal sphincter injuries; 146 followed an invitation for follow-up. INTERVENTIONS: Clinical examination, anal manometry, and translabial ultrasound were performed. MAIN OUTCOME MEASURES: The primary outcomes measured were the St Mark incontinence score and the evidence of sphincter disruption on translabial ultrasound. RESULTS: Of 372 contactable patients, 146 attended at a mean follow-up of 6.6 years (1.7-11.9), of which 75 (51%) reported symptoms of anal incontinence with a median "bother score" of 6 (interquartile range, 3-8). Median St Mark score was 3 (interquartile range, 2-5). Twenty-four (16%) had a score of ≥5. Women who had been diagnosed with a 3c/4th degree tear had more symptoms (58% vs 44%), significantly lower mean maximal resting pressure (p < 0.001), maximal squeeze pressure (p < 0.001), and more residual external (p < 0.001) and internal (p = 0.012) sphincter defects in comparison with those who had a 3a/3b tear. Women with residual external sphincter defects had lower mean maximal squeeze pressure (p = 0.02). Residual internal sphincter defects (p = 0.001) and levator avulsion (p = 0.048) are independent risk factors for anal incontinence on multivariate modeling. LIMITATIONS: This study was limited by the lack of predelivery data of bowel symptoms and BMI and incomplete intrapartum documentation of tear grade. CONCLUSIONS: Symptoms of anal incontinence were highly prevalent (51%), with a high bother score of 6. St Mark scores were associated with residual internal anal sphincter defects and levator avulsion. Women who had a higher tear grade showed a higher incidence of residual sphincter defects and lower manometry pressures. See Video Abstract at http://links.lww.com/DCR/A824.

Atraumatic normal vaginal delivery: how many women get what they want?

BACKGROUND: Trauma to the perineum, levator ani complex, and anal sphincter is common during vaginal childbirth, but often clinically underdiagnosed, and many women are unaware of the potential for long-term damage. OBJECTIVE: In this study we use transperineal ultrasound to identify how many women will achieve a normal vaginal delivery without substantial damage to the levator ani or anal sphincter muscles, and to create a model to predict patient characteristics associated with successful atraumatic normal vaginal delivery. STUDY DESIGN: This is a retrospective, secondary analysis of data sets gathered in the context of an interventional perinatal imaging study. A total of 660 primiparas, carrying an uncomplicated singleton pregnancy, underwent an antepartum and postpartum interview, vaginal exam (Pelvic Organ Prolapse Quantification), and 4-dimensional translabial ultrasound. Ultrasound data were analyzed for levator trauma and/or overdistention and residual sphincter defects. Postprocessing analysis of ultrasound volumes was performed blinded against clinical data and analyzed against obstetric data retrieved from the local maternity database. Levator avulsion was diagnosed if the muscle insertion at the inferior pubic ramus at the plane of minimal hiatal dimensions and within 5 mm above this plane on tomographic ultrasound imaging was abnormal, ie the muscle was disconnected from the inferior pubic ramus. Hiatal overdistensibility (microtrauma) was diagnosed if there was a peripartum increase in hiatal area on Valsalva by >20% with the resultant area ≥25 cm2. A sphincter defect was diagnosed if a gap of >30 degrees was seen in ≥4 of 6 tomographic ultrasound imaging slices bracketing the external anal sphincter. Two models were tested: a first model that defines severe pelvic floor trauma as either obstetric anal sphincter injury or levator avulsion, and a second, more conservative model, that also included microtrauma. RESULTS: A total of 504/660 women (76%) returned for postpartum follow-up as described previously. In all, 21 patients were excluded due to inadequate data or intercurrent pregnancy, leaving 483 women for analysis. Model 1 defined nontraumatic vaginal delivery as excluding operative delivery, obstetric anal sphincter injuries, and sonographic evidence of levator avulsion or residual sphincter defect. Model 2 also excluded microtrauma. Of 483 women, 112 (23%) had a cesarean delivery, 103 (21%) had an operative vaginal delivery, and 17 (4%) had a third-/fourth-degree tear, leaving 251 women who could be said to have had a normal vaginal delivery. On ultrasound, in model 1, 27 women (6%) had an avulsion and 31 (6%) had a residual defect, leaving 193/483 (40%) who met the criteria for atraumatic normal vaginal delivery. In model 2, an additional 33 women (7%) had microtrauma, leaving only 160/483 (33%) women who met the criteria for atraumatic normal vaginal delivery. On multivariate analysis, younger age and earlier gestation at time of delivery remained highly significant as predictors of atraumatic normal vaginal delivery in both models, with increased hiatal area on Valsalva also significant in model 2 (all P ≤ .035). CONCLUSION: The prevalence of significant pelvic floor trauma after vaginal child birth is much higher than generally assumed. Rates of obstetric anal sphincter injury are often underestimated and levator avulsion is not included as a consequence of vaginal birth in most obstetric text books. In this study less than half (33-40%) of primiparous women achieved an atraumatic normal vaginal delivery.