Persistence of levator ani sonographic defect detected by three-dimensional transperineal sonography in primiparous women

The Association Between Levator Ani Integrity and Postpartum Ano-Rectal Dysfunction: A Systematic Review

INTRODUCTION AND HYPOTHESIS

Pregnancy and delivery are commonly associated with ano-rectal dysfunction. In addition, vaginal delivery may impact both the structure and functionality of the pelvic floor. Herein, we systematically reviewed the literature for the potential association between levator ani muscle (LAM) avulsion and ano-rectal function after childbirth.

METHODS

We systematically searched the PubMed, EMBASE, CINAHL, Web of Science Core Collection, CENTRAL (Cochrane), Clinicaltrials.gov, and ICTRP databases from inception. We selected studies reporting on the anatomy of the LAM and ano-rectal function within 24 months after childbirth, the former determined by imaging and the latter measured through validated questionnaires or ano-rectal manometry. Meta-analyses were used to pool data from studies reporting on the association between LAM avulsion and ano-rectal function, with subgroup analysis according to the presence or absence of anal sphincter trauma. Summary odds ratio (OR) and mean difference (MD) are reported with 95% confidence intervals.

RESULTS

From the 7,621 studies identified, 11 were included, reporting on 2,146 women. Ten studies used transperineal ultrasound (TPUS) and one study used magnetic resonance imaging (MRI) for LAM assessment. Ano-rectal function was assessed through validated questionnaires in all but one study, in which ano-rectal manometry was used. There was no evidence for an association between LAM avulsion and symptoms of incontinence (OR 1.75 [0.74, 4.12]; MD 0.13 [-0.58, 0.85]), including in the subgroup of patients with concomitant anal sphincter injury (OR 1.83 [0.71, 4.71]).

CONCLUSIONS

We did not identify an association between LAM avulsion and ano-rectal dysfunction following vaginal childbirth.

Do some levator avulsions improve over time?

OBJECTIVE

To determine whether the sonographic appearance of levator ani muscle avulsion after vaginal birth can improve significantly over the first few years postpartum.

METHODS

This was a retrospective study of women seen in the context of two prospective perinatal imaging studies. All subjects had undergone an interview, clinical examination and four-dimensional translabial ultrasound on average 4.3 months and 3.1 years postpartum. Volume datasets were analyzed at a later date, with the examiner blinded against all other data. The number of abnormal slices at both timepoints was compared using the Mann-Whitney U-test. Patients in whom findings had changed over time were reviewed separately, in parallel, in order to reduce the impact of differences in slice location and imaging settings. The symmetry test was used to analyze changes between the two postnatal visits.

RESULTS

Of 1148 women recruited originally, 315 attended at least two postnatal visits. Forty-two were excluded, leaving 273 women for the final analysis. The mean time of first follow-up was 4.3 (range, 2.6-9.8) months after their first birth and the mean time of last follow-up was 3.1 (range, 1.4-8.0) years postpartum. Cohen's κ for the category of avulsion (normal, partial avulsion and full avulsion) at the two assessments was 0.89, with agreement in 97% (264/273) of cases. At the first visit, full levator ani muscle avulsion was diagnosed in 20, partial avulsion in 32 and no avulsion in 221 women. While seven partial avulsions appeared sonographically normal at the second visit, there were no statistically significant changes in avulsion category between visits (P = 0.4).

CONCLUSIONS

Tomographic pelvic floor imaging obtained 3-10 months after childbirth may be used as a proxy for long-term outcomes. Ultrasound findings at a mean of 3.1 years postpartum showed 97% agreement with findings obtained on imaging at a mean of 4.3 months postpartum. There was a non-significant reduction in abnormal slices at the second follow-up visit, affecting at most 3/12 slices. This may be explained by compensatory hypertrophy of the remaining intact muscle. Sonographic normalization of full levator ani muscle avulsion was not observed. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Prevalence of levator ani muscle injuries in primiparous women after delivery and their influence on pelvic floor disorders-systematic review

BACKGROUND

Studies show a significant association between the first vaginal delivery and injuries of the levator ani muscle (LAM), which can cause pelvic floor disorders (PFDs).

OBJECTIVES

This study aims to identify the prevalence of short and long-term LAM injuries after vaginal delivery in primiparous women and its influence on PFDs.

METHOD

A systematic review was conducted according to the PRISMA methodology. The databases used were Pubmed, Cochrane, and PEDro. The quality assessment of the evidence was carried out using the Critical Appraisal Skills Programme (CASP). Both the selection of studies and their evaluation were done by two researchers and a third reviewer in cases of disagreement.

RESULTS

From the search, 57 articles were gathered, and 19 were included to match the eligibility criteria. The prevalence of avulsion of the LAM was found in association with vaginal delivery between 13% and 28% ≤ 1 year after delivery and between 16% and 29% > 1 year after delivery. Ballooning was detected between 20% and 37% ≤ 1 year, and 33% of women > 1 year after delivery, appearing to be more common when compared to avulsion. Pelvic organ prolapse (POP) was considered the most common disorder associated with injuries of the LAM, and there seems to be some connection with sexual dysfunction.

CONCLUSION

Avulsion of the LAM and ballooning of the hiatal area have a high prevalence in primiparous women after vaginal delivery and have a strong direct relation to the development of POP.

Levator ani muscle avulsion and subsequent vaginal delivery: 8-year longitudinal follow-up

OBJECTIVES

To assess the evolution of levator ani muscle (LAM) avulsion from 1 year to 8 years after first delivery in women with and those without subsequent vaginal delivery. In addition, to assess whether women with full or partial avulsion 8 years after first delivery have larger LAM hiatal area and more symptoms of pelvic organ prolapse compared to women with normal LAM insertion.

METHODS

In this single-center longitudinal study, 195 women who were primiparous at the start of the study were included and underwent transperineal ultrasound examination 1 year and 8 years after first delivery. Muscle insertion was assessed by tomographic ultrasound imaging in the axial plane. Full LAM avulsion was defined as abnormal muscle insertion in all three central slices. Partial LAM avulsion was defined as abnormal muscle insertion in one or two central slices. Eight years after the first delivery, LAM hiatal area was assessed at rest, during maximum pelvic floor muscle contraction and on maximum Valsalva maneuver. To assess symptoms of pelvic organ prolapse, the vaginal symptoms module of the International Consultation on Incontinence Questionnaire was used.

RESULTS

At 1-year follow-up, 25 (12.8%) women showed signs of LAM avulsion, of whom 20 fulfilled the sonographic criteria of full avulsion and five of partial avulsion. Eight years after the first delivery, 35 (17.9%) women were diagnosed with avulsion, of whom 25 were diagnosed with full avulsion and 10 with partial avulsion. No woman with partial or full avulsion at 1 year had improved avulsion status at 8-year follow-up. Of the 150 women who had subsequent vaginal delivery, 21 (14.0%) women were diagnosed with partial or full LAM avulsion 1 year after first delivery, and 31 (20.7%) women were diagnosed with partial or full avulsion 8 years after first delivery. Of the 45 women without subsequent vaginal delivery, one woman with partial avulsion 1 year after first delivery was diagnosed with full avulsion at 8-year follow-up. All women with full avulsion at 1-year follow-up were diagnosed with full avulsion at 8-year follow-up regardless of whether they had subsequent vaginal delivery. At 8-year follow-up, women with full avulsion had statistically significantly larger LAM hiatal area compared to women with normal muscle insertion. Mean ± SD vaginal symptom scores ranged between 5.5 ± 5.7 and 6.0 ± 4.0 and vaginal symptom quality of life scores ranged between 0.9 ± 1.4 and 1.5 ± 2.2 and did not differ significantly between women with normal muscle insertion and women with partial or full avulsion at 8-year follow-up.

CONCLUSIONS

More LAM avulsions were present 8 years compared with 1 year after first delivery in women with subsequent vaginal delivery. Except for one primipara, all women without subsequent vaginal delivery had unchanged LAM avulsion status between 1 year and 8 years after their first delivery. Larger LAM hiatal area was found in women with full avulsion compared to those with normal muscle insertion at 8-year follow-up. Vaginal symptoms scores were low and did not differ between women with normal muscle insertion and those with partial or full avulsion at 8-year follow-up. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Multicenter study of the evolution of different types of avulsion over the 12 months after delivery

OBJECTIVE

To perform a multicenter study of muscle recovery in levator ani muscle (LAM) avulsion during the first 12 months postpartum according to the type of LAM avulsion suffered.

METHODS

This was a multicenter prospective observational study including 242 primiparas. Transperineal ultrasound was performed at 6 months and 12 months after delivery. Type I LAM avulsion was present when most of the lateral fibers of the pubovisceral muscle were observed at the muscle's insertion at the pubic level. Type II LAM avulsion was defined as complete detachment of the pubovisceral muscle from its insertion at the pubic level.

RESULTS

Among the 56 patients who completed the study (with ultrasound at 6 and 12 months after delivery), 76 avulsions (10 cases of bilateral avulsion) were identified at 6 months after delivery, and the total number of avulsions had decreased to 58 at 12 months after delivery (P < 0.001; 95% confidence interval [CI] 13.9%-33.5%). This decrease was due to the disappearance of 69.2% of the cases of Type I LAM avulsions (P < 0.001; 95% CI: 50.2%-88.2%). However, the number of Type II LAM avulsions remained constant at 6 months and 12 months after delivery.

CONCLUSION

The spontaneous resolution of LAM avulsion during the first 12 months postpartum occurs in cases of Type I LAM avulsion but is not observed in Type II LAM avulsion.

A review of levator ani avulsion after childbirth: Incidence, imaging and management

Key Content • Levator ani muscle (LAM) avulsion injury occurs occultly during childbirth, most commonly during operative vaginal deliveries. • Injuries of levator ani have long term sequelae for pelvic floor health. As life expectancy increases the burden of disease upon urogynaecology services will need to be considered. • Diagnosis of this condition can be difficult as there is no agreed 'gold standard' imaging modality. • There is no consensus regarding surgical management of LAM avulsion. Learning objectives • Review anatomy and function of levator ani muscle • Identify the risk factors for levator ani avulsion injury • Role of imaging to appropriately identify LAM injury and current management options including appropriate follow up • Management of subsequent pregnancy following LAM avulsion Ethical issues • Is there value to the patient in diagnosing levator ani avulsion when there is no recommended treatment for these injuries?

Development and validation of a composite AI model for the diagnosis of levator ani muscle avulsion

OBJECTIVE

To assess the feasibility and reliability of a composite AI model for the diagnosis of levator ani muscle (LAM) avulsion of tomographic ultrasound imaging (TUI).

METHODS

Ultrasonic images of the pelvic floor from a total of 304 patients taken from January 2018 to October 2020 were included. All patients included underwent standardized interviews and transperineal ultrasound (TPUS). Transfer-learning and ensemble-learning methods were adopted to develop the proposed model on the basis of three classic convolutional neural networks (CNN). Confusion matrix (CM) and the ROC statistic were used to assess the effectiveness of the proposed model. Gradient-weighted class activation mappings (Grad-CAMs) were used to help enhance the interpretability of the proposed model.

RESULTS

Of the 304 patients included, 208 were in the derivation cohort (108 LAM avulsion and 100 normal) and 96 (39 LAM avulsion and 57 normal) were in the validation cohort. The proposed model in LAM avulsion diagnosis outperformed other models and a junior clinician in both the test set of derivation cohort and the validation cohort, with accuracies of 0.95 and 0.81, and AUCs of 0.98 and 0.86, respectively. According to the heatmap of Grad-CAMs, the proposed model mainly localizes areas between the pubic symphysis and the bilateral insertion point of LAM when making a diagnosis, which is exactly the region of interest in clinical practice.

CONCLUSION

The proposed model using ultrasonic images of the pelvic floor may be a promising tool in assisting the diagnosis of LAM avulsion in clinical practice.

KEY POINTS

• First AI-assisted model for levator ani muscle avulsion diagnosis • Diagnosis accuracy of less-experienced clinicians could be improved using the proposed model.

The evolution of levator ani muscle trauma over the first 9 months after vaginal birth

INTRODUCTION AND HYPOTHESIS

The objective was to investigate the evolution of levator ani muscle (LAM) trauma over the first 9 months after birth and to evaluate their agreement between different assessment periods.

METHODS

From March 2017 to April 2019 we prospectively evaluated LAM states (intact, hematoma, partial or complete avulsion) of primiparous women after vaginal birth by using 4D translabial ultrasound (TLUS) at three different assessment periods. All women were examined 1-4 days (A1) and 6-10 weeks (A2) postpartum, and women with a trauma additionally 6-9 months postpartum (A3). Cohen's Kappa analysis was performed to evaluate the test agreement between the assessment periods.

RESULTS

Thirty-two percent of the women at A1 had a LAM trauma and 24% at A2. The higher number of LAM injuries at A1 can be explained by hematomas (14%), of which 51% spontaneously resolved at A2, 35% revealed themselves as partial, and 12% as complete avulsions. At A3, we observed anatomical improvement from complete to partial avulsions (23%) and few partial avulsions changed into an intact LAM (3%); none of the complete avulsions changed into an intact LAM. The agreement of 4D TLUS between A1 and A2 was moderate to good (0.64 for the right-sided LAM/0.60 for the left-sided LAM) and between A2 and A3 good to very good (0.76 right-sided/0.84 left-sided).

CONCLUSIONS

Levator ani muscle trauma can reliably be diagnosed during all assessment periods. However, the agreement between A1 and A2 was only moderate to good. This can be explained by hematomas inside the LAM that were only observed early postpartum. We observed some anatomical improvement at A3, but no complete avulsion improved to an intact LAM.

Obstetric anal sphincter injury in adolescent mothers

Background

Obstetric anal sphincter injury (OASI) is a debilitating complication of vaginal delivery which has yet to receive ample attention in adolescents. The aim of this study was to describe risk for OASI in adolescent mothers compared to adults. We further attempted to compare risk factors for OASI between these two age groups.

Methods

We performed a retrospective cohort study between 2003 and 2019. Primiparous women who delivered vaginally, 21 years and younger were compared to women ages 26–35. Excluded were preterm, multifetal, non-vertex, cesarean deliveries as well as intrauterine fetal death. Rate of OASI as well as obstetric and labor characteristics of women with OASI, were compared between groups. Finally, risk factors were assessed for each group separately. Univariate and multivariate logistic regression model were performed.

Results

Final analysis was performed on 5113 nulliparous adolescents and 13,845 nulliparous in the 26–35 age group. Allocation to study groups was according to OASI – Sixty-seven adolescents (1.3%) had a 3rd or 4th degree perineal tear and were defined as the OASI group, while 5046 patients (98.7%) did not have such a tear. In the adult group, 199 out of 13,845 patients (1.4%) were diagnosed with OASI. Occurrence of OASI did not differ between groups (p = 0.510). Comparison of women with OASI in the adolescent group vs. adult group found differences with regard to operative vaginal delivery, (20.9% vs. 36.2%, respectively; p = 0.023) and meconium stained amniotic fluid (9.1% vs. 21.3%, respectively; p = 0.027).

Following multivariate analysis the only parameter independently associated with OASI in the adolescent age group was head circumference ≥ 90th percentile with an adjusted odds ratio of 3.08 (CI 1.48–6.38, p = 0.003). In the adult group the similar analysis revealed operative vaginal delivery (OR = 2.44, CI 1.72–3.47, p < 0.001) and a birthweight≥90th percentile (OR = 2.23, CI 1.19–4.18, p = 0.012) to be independent risk factors for OASI.

Conclusion

Adolescents have similar risk for OASI compared to adults but differ in risk factors leading to OASI. Head circumference ≥ 90th percentile was found to be associated with OASI in this age group.

Ultrasonographic evaluation of pelvic floor structure at antepartum and postpartum periods using three-dimensional transperineal ultrasound

PURPOSE

To examine the changes in the pelvic floor structure caused by pregnancy and delivery.

METHODS

A total of 141 nulliparous women were examined with three-dimensional transperineal ultrasound (3D-TPU) at the 24th and 34th weeks of gestation, 5th day postpartum, and 1 month postpartum. Puborectalis muscle trauma was diagnosed and the area of levator hiatus (ALH) was measured.

RESULTS

One hundred and five normal vaginal deliveries, 19 vacuum/forceps deliveries, and 17 cesarean deliveries were included. In the normal delivery group, the rate of puborectalis muscle trauma was low and showed no significant change between the 24th and 34th weeks of gestation (12.5% vs. 17.2%, p = 0.42). The rate of trauma significantly increased to 70.2% at the 5th day postpartum (p < 0.001). There was no significant difference between the rates at the 5th day postpartum and 1 month postpartum (73.7%, p = 0.60). The same trend was found in the vacuum/forceps group. In the cesarean section group, no significant change was observed throughout pregnancy and postpartum periods. In the normal delivery group, ALH significantly increased between the 24th and 34th week (14.1 ± 2.6 cm² vs. 14.6 ± 3.4 cm², p = 0.007). ALH markedly increased to 20.9 ± 4.8 cm² at the 5th day postpartum (p < 0.001). ALH at 1 month postpartum decreased to 17.0 ± 4.3 cm² (p < 0.001), but did not return to the value at the 24th week (p < 0.001).

CONCLUSIONS

Vaginal childbirth results in enlargement of the levator hiatus. Pelvic floor muscles in pregnant women are affected not only by mechanical damage associated with delivery but also by physiologic changes during pregnancy. The effects of pregnancy and delivery on pelvic floor muscles may persist after delivery.

Type of levator ani muscle avulsion as predictor for the disappearance of avulsion

OBJECTIVES

The objective of our study was to establish whether the type of levator ani muscle (LAM) avulsion diagnosed 6 months after delivery influences the integrity of the LAM at 1 year after delivery and determine its influence on the levator hiatus area.

STUDY DESIGN

This observational prospective cohort study included 192 primiparous women with vaginal delivery. Transperineal ultrasound examinations were performed at 6 months and 1 year postpartum. Levator hiatus measurements (anteroposterior diameter, transverse diameter, and area) were performed in the plane of minimal dimensions. Complete avulsion was defined based on maximum contraction in multislice mode. Type I LAM avulsion was present when most lateral fibers of the pubovisceral muscle were observed at its insertion at the pubic level (the arch of the elevator remained intact). Type II LAM avulsion was defined as a complete detachment of the pubovisceral muscle from its insertion at the pubic level.

RESULTS

In total, 192 patients were recruited after delivery; 48 patients were diagnosed with complete LAM avulsion, and 13 patients with avulsion did not attend the second ultrasound follow-up at 1 year after delivery. Thirty-five patients with complete LAM avulsion were included in the study. At 6 months after delivery, 51 LAM avulsions were observed in 35 patients (including bilateral LAM avulsion in 16 cases), of which 54.9% were right avulsions and 45.1% left avulsions. Furthermore, 11 (five right and six left) were type I LAM avulsions at the 6-month assessment, and all of these had disappeared 1 year after delivery. However, none of the type II LAM avulsions (23 right and 17 left) observed at 6 months had disappeared at the second ultrasound examination. There were no differences between the LAM areas detected at the first and second ultrasound examinations (10.2 ± 3.3 vs 9.3 ± 1.8; P = .404).

CONCLUSIONS

The type of LAM avulsion observed at 6 months after childbirth predicts LAM persistence at 1 year postpartum.

Change in prevalence of major levator ani muscle defects from 6 weeks to 1 year postpartum, and maternal and obstetric risk factors: A longitudinal ultrasound study

INTRODUCTION

The present study aimed first to investigate the change in prevalence of major levator ani muscle (LAM) defects, also called avulsions, from 6 weeks to 1 year postpartum, and second to assess maternal and obstetric risk factors for having persistent major LAM defects/avulsions at 1 year postpartum.

MATERIAL AND METHODS

This is a secondary analysis of data from a prospective cohort study including 300 nulliparous women at 17-19 weeks of gestation. Major LAM defects were diagnosed at 6 weeks and 1 year postpartum using transperineal ultrasonography. We defined persistent major LAM defects as a defect diagnosed both at 6 weeks and 1 year postpartum. Maternal and obstetric data were obtained from the hospital's electronic birth records. Pelvic floor muscle function was measured vaginally by manometer at 21 weeks of gestation. The main outcome measurement was change in prevalence of major LAM defects. Maternal and obstetric risk factors for having persistent major LAM defect were also assessed.

RESULTS

Prevalence of major LAM defects was 19.4% at 6 weeks and 10.4% at 1 year postpartum. No new major LAM defects were diagnosed at 1 year postpartum. Persisting major LAM defects were associated with longer second stage of labor (median 74.5 minutes vs median 48.0 minutes, P = .012) and higher neonatal birthweight (mean difference of 232.3 g, 95% confidence interval [CI] 21.5-443.1). Vacuum delivery was independently associated with persistent major LAM defects, adjusted OR 3.0 (95% CI 1.0-9.0).

CONCLUSIONS

There was a 50% reduction of sonographically diagnosed major LAM defects from 6 weeks to 1 year postpartum. This finding suggests that assessment of the major LAM 6 weeks postpartum may be too early to diagnose defects/avulsions. Long second stage of labor, high neonatal birthweight and vacuum delivery were associated with persistent major LAM defects/avulsions.

Longitudinal follow-up of levator ani muscle avulsion: does a second delivery affect it?

OBJECTIVES

To evaluate the morphological outcome of levator ani muscle (LAM) avulsion 3-5 years after a first delivery and to assess the effect of a second delivery on this condition. The impact of LAM avulsion on pelvic floor disorders was also studied.

METHODS

Six hundred and sixty-six women who had been assessed for LAM avulsion 8 weeks after their first delivery were invited for a follow-up examination 3-5 years later. Women completed the Pelvic Floor Distress Inventory including the Urinary Distress Inventory (UDI) and Pelvic Organ Prolapse Distress Inventory (POPDI) questionnaires to explore symptoms of pelvic floor disorders, and the pelvic floor was examined using three-dimensional translabial ultrasound and assessed using the pelvic organ prolapse quantification system.

RESULTS

Three hundred and ninety-nine women completed the study, of whom 151 were multiparous. Mean interval between first delivery and follow-up was 42.3 ± 7.6 months. Among 69 women who had LAM avulsion 8 weeks after their first delivery, nine (13.0%) had no LAM avulsion at follow-up. One (0.9%) woman had a new LAM avulsion after her second vaginal delivery. A greater proportion of women with LAM avulsion reported symptoms of stress urinary incontinence (SUI) (adjusted odds ratio, 2.09 (95% CI, 1.18-3.70); P = 0.01) and symptoms of prolapse than did women without avulsion; however, this difference did not reach statistical significance (P = 0.61). Women with LAM avulsion had higher UDI and POPDI scores than did women without avulsion (median UDI score, 17.7 (interquartile range (IQR), 5.0-32.4) vs 9.2 (IQR, 0.0-22.1); P = 0.045 and median POPDI score, 20.8 (IQR, 8.8-40.5) vs 10.7 (IQR, 0.0-32.8); P = 0.021).

CONCLUSIONS

The risk of developing new LAM avulsion after a second vaginal delivery is low (0.9%). Healing of LAM avulsion was observed in 13% of women who had at least one vaginal delivery. At 3-5 years after delivery, women with LAM avulsion reported symptoms of SUI more often than did those without, and had higher UDI and POPDI scores, implying more bothersome symptoms. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Third- or Fourth-Degree Intrapartum Anal Sphincter Tears Are Associated With Levator Ani Avulsion in Primiparas

OBJECTIVES

We evaluated primiparous women with clinically diagnosed third- and fourth-degree and anal sphincter tears, to evaluate the rate of levator ani muscle injury compared to primiparous women without sphincter tears.

METHODS

Primiparous women delivering in our maternity ward with intrapartum diagnoses of third- or fourth-degree anal sphincter tears, repaired by the overlapping technique, were recruited to undergo 3-dimensional transperineal sonography of the pelvic floor anatomy, including the anterior and posterior compartments. Primiparas with uncomplicated vaginal deliveries were recruited as a comparison group. Patient files were examined, and maternal backgrounds and delivery and neonatal details were extracted for all patients.

RESULTS

Ninety-four women with tears were recruited to the study group, and 464 women with normal vaginal deliveries constituted the comparison group. The groups differed significantly in the rates of levator ani defects: 38 of 94 women (40.4%) in the study group versus 75 of 464 (16.2%) in the comparison group (P < .001; odds ratio, 3.53; 95% confidence interval, 2.18–5.7). Neonatal head circumference differed significantly between the study and comparison groups: (mean ・} SD, 34.5 ・} 1.3 cm in the study group versus 33.9 ・} 1.3 cm in the comparison group; P= .005), as did birth weight (3322 ・} 430 g in the study group versus 3169 ・} 458 g in the comparison group; P= .007). The groups did not differ in maternal age, gestational age at delivery, length of second stage of labor, and rates of epidural anesthesia, episiotomy, and vacuum extraction.

CONCLUSIONS

Third- and fourth-degree intrapartum sphincter tears are associated with levator ani avulsion. Knowledge of complex pelvic floor damage may allow for prompt referral to secondary preventive measures for pelvic floor disorders.