Morphometry of the nulliparous pelvic floor

Soft-tissue dystocia due to paradoxical contraction of the levator ani as a cause of prolonged second stage: concept, diagnosis, and potential treatment

Smaller pelvic floor dimensions seem to have been an evolutionary need to provide adequate support for the pelvic organs and the fetal head. Pelvic floor dimension and shape contributed to the complexity of human birth. Maternal pushing associated with pelvic floor muscle relaxation is key to vaginal birth. Using transperineal ultrasound, pelvic floor dimensions can be objectively measured in both static and dynamic conditions, such as pelvic floor muscle contraction and pushing. Several studies have evaluated the role of the pelvic floor in labor outcomes. Smaller levator hiatal dimensions seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Furthermore, smaller levator hiatal dimensions are associated with a higher fetal head station at term of pregnancy, as assessed by transperineal ultrasound. With maternal pushing, most women can relax their pelvic floor, thus increasing their pelvic floor dimensions. Some women contract rather than relax their pelvic floor muscles under pushing, which is associated with a reduction in the anteroposterior diameter of the levator hiatus. This phenomenon is called levator ani muscle coactivation. Coactivation in nulliparous women at term of pregnancy before the onset of labor is associated with a higher fetal head station at term of pregnancy and a longer duration of the second stage of labor. In addition, levator ani muscle coactivation in nulliparous women undergoing induction of labor is associated with a longer duration of the active second stage of labor. Whether we can improve maternal pelvic floor relaxation with consequent improvement in labor outcomes remains a matter of debate. Maternal education, physiotherapy, and visual feedback are promising interventions. In particular, ultrasound visual feedback before the onset of labor can help women increase their levator hiatal dimensions and correct levator ani muscle coactivation in some cases. Ultrasound visual feedback in the second stage of labor was found to help women push more efficiently, thus obtaining a lower fetal head station at ultrasound and a shorter duration of the second stage of labor. The available evidence on the role of any intervention aimed to aid women to better relax their pelvic floor remains limited, and more studies are needed before considering its routine clinical application.

Are pelvic pain and increased pelvic floor muscle tone associated in women with persistent noncancer pelvic pain? A systematic review and meta-analysis

BACKGROUND

The association between pelvic pain and pelvic floor muscle (PFM) tone in women with persistent noncancer pelvic pain (PNCPP) is unclear.

AIM

To synthesize the evidence of the association between pelvic pain and PFM tone in women with PNCPP.

METHODS

A systematic review was conducted via MEDLINE, Emcare, Embase, CINAHL, PsycINFO, and Scopus to identify relevant studies. Studies were eligible if pelvic pain and PFM tone outcome measures were reported among women aged >18 years. The National Heart, Lung, and Blood Institute's Quality Assessment Tool for Observational Cohort and Cross-sectional Studies was used to assess study quality. Studies were pooled by assessment of PFM tone via a random effects model. Associations between the presence of pelvic pain and PFM tone were assessed with odds ratio (OR), while linear associations were assessed with Pearson or Spearman correlation.

OUTCOMES

Pelvic pain measures (intensity, threshold, and frequency) and resting PFM tone in women with PNCPP, as evaluated by any clinical assessment method or tool.

RESULTS

Twenty-four studies were included in this review. The presence of pelvic pain was significantly associated with increased PFM tone as assessed by digital palpation (OR, 2.85; 95% CI, 1.66-4.89). Pelvic pain intensity was inversely but weakly associated with PFM flexibility when evaluated through dynamometry (r = -0.29; 95% CI, -0.42 to -0.17). However, no significant associations were found between pelvic pain and PFM tone when measured with other objective assessment methods.

CLINICAL IMPLICATIONS

Pelvic pain and increased PFM tone may not be directly associated; alternatively, a nonlinear association may exist. A range of biopsychosocial factors may mediate or moderate the association, and clinicians may need to consider these factors when assessing women with PNCPP.

STRENGTHS AND LIMITATIONS

This review was reported according to the PRISMA guidelines. All possible findings from relevant theses and conference abstracts were considered in our search. However, nonlinear associations between pelvic pain and increased PFM tone were not assessed as part of this review.

CONCLUSION

Pelvic pain may be linearly associated with increased PFM tone and decreased PFM flexibility when measured with digital palpation or dynamometry; however, this association was not observed when other aspects of PFM tone were assessed through objective methods. Future studies are required using robust assessment methods to measure PFM tone and analyses that account for other biopsychosocial factors that may influence the association.

Factors involved in changes in the levator ani during pregnancy

INTRODUCTION AND HYPOTHESIS

Levator ani muscle (LAM) dimensions increase during pregnancy to allow the delivery of the fetus. The objective was to investigate which factors are involved in LAM modifications during pregnancy.

METHODS

A prospective longitudinal observational study was conducted between July 2015 and March 2018. Ninety-nine nulliparous pregnant women were included. Data on the physical examination, 4D transperineal ultrasound and hormonal concentrations (progesterone, oestradiol and relaxin) were collected during the first and third trimesters.

RESULTS

We found higher hiatal dimensions at the beginning of pregnancy than in other studies with nonpregnant women. Increases in the levator ani hiatal (LH) dimensions were observed at contraction (1.01 ±1.96 cm2), rest (0.82 ± 2.51 cm2) and on Valsalva (2.36 ± 3.64 cm2) throughout pregnancy. The distensibility in the third trimester was higher than in the first trimester (5.79 vs 4.24 cm2; p=0); however, the contractility was lower (-3.32 vs -3.5 cm2; p=0.04). Women with lower scores on the Modified Oxford Grading Scale in the third trimester presented with lower contractility in the LAM. A larger LH at the end of pregnancy was associated with age and body mass index. Eleven women developed ballooning during pregnancy; in these women, relaxin was higher in both trimesters than in women without ballooning, but these results were not statistically significant. The linear models to predict third-trimester Valsalva LH, distensibility and contractility were not conclusive and did not show any factors to predict LAM modifications during pregnancy.

CONCLUSIONS

Hormones could play a role in modifying the muscle properties of LAM from the beginning of pregnancy, but we did not find an association between LAM measurements and hormone concentration in this study.

Is there a difference in pelvic floor muscle tone between women with and without pelvic pain? A systematic review and meta-analysis

BACKGROUND

Alterations in pelvic floor muscle (PFM) function have been observed in women with persistent noncancer pelvic pain (PNCPP) as compared with women without PNCPP; however, the literature presents conflicting findings regarding differences in PFM tone between women with and without PNCPP.

AIM

To systematically review the literature comparing PFM tone in women with and without PNCPP.

METHODS

MEDLINE, Embase, Emcare, CINAHL, PsycINFO, and Scopus were searched from inception to June 2021 for relevant studies. Studies were included that reported PFM tone data in women aged ≥18 years with and without PNCPP. The risk of bias was assessed with the National Heart, Lung, and Blood Institute Quality Assessment Tool. Standardized mean differences (SMDs) for PFM tone measures were calculated via random effects models.

OUTCOMES

Resting PFM tone parameters, including myoelectrical activity, resistance, morphometry, stiffness, flexibility, relaxation, and intravaginal pressure, measured by any clinical examination method or tool.

RESULTS

Twenty-one studies met the inclusion criteria. Seven PFM tone parameters were measured. Meta-analyses were conducted for myoelectrical activity, resistance, and anterior-posterior diameter of the levator hiatus. Myoelectrical activity and resistance were higher in women with PNCPP than in women without (SMD = 1.32 [95% CI, 0.36-2.29] and SMD = 2.05 [95% CI, 1.03-3.06], respectively). Women with PNCPP also had a smaller anterior-posterior diameter of the levator hiatus as compared with women without (SMD = -0.34 [95% CI, -0.51 to -0.16]). Meta-analyses were not performed for the remaining PFM tone parameters due to an insufficient number of studies; however, results of these studies suggested greater PFM stiffness and reduced PFM flexibility in women with PNCPP than in women without.

CLINICAL IMPLICATIONS

Available evidence suggests that women with PNCPP have increased PFM tone, which could be targeted by treatments.

STRENGTHS AND LIMITATIONS

A comprehensive search strategy was used with no restriction on language or date to review studies evaluating PFM tone parameters between women with and without PNCPP. However, meta-analyses were not undertaken for all parameters because few included studies measured the same PFM tone properties. There was variability in the methods used to assess PFM tone, all of which have some limitations.

CONCLUSION

Women with PNCPP have higher PFM tone than women without PNCPP; therefore, future research is required to understand the strength of the relationship between pelvic pain and PFM tone and to investigate the effect of treatment modalities to reduce PFM tone on pelvic pain in this population.

Effect of exercise on female pelvic floor morphology and muscle function: a systematic review

INTRODUCTION AND HYPOTHESIS

The objective was to synthesize the scientific evidence on the relationship of exercise with morphology and muscle function parameters of the female pelvic floor. The design was a systematic review.

METHODS

Searches were performed in MEDLINE, PubMed, CINAHL, Web of Science, SCOPUS, SportDiscuss, and Google Scholar up to April 2021. Observational and experimental studies evaluating the morphology and/or function of the pelvic floor muscles (PFMs) in women were eligible. Studies reporting exercise or sports disciplines as exposure/intervention were included.

RESULTS

Twenty-five studies were included. Compared with the control group, women performing vigorous and high-impact exercises exhibited lower maximum voluntary contraction of the PFM and those performing moderate exercise had better maximum voluntary contraction. Exercise practitioners had a larger hiatal area at rest, during contraction, and during Valsalva, and greater bladder neck descent than the control group.

CONCLUSIONS

The results of this review demonstrate an inverse relationship of PFM maximum voluntary contraction with exercise intensity. Qualitative synthesis showed that the studies found favorable outcomes for the control group in terms of hiatal area during contraction and Valsalva and bladder neck displacement.

Pelvic organ prolapse in nulliparae

Background

Pregnancy and childbirth are thought to be the strongest environmental risk factors for pelvic organ prolapse, but prolapse does occur in nulliparae.

Aim

To characterise prolapse in vaginal nulliparae.

Material and methods

This was a retrospective study using archived clinical and imaging data of 368 vaginally nulliparous women seen between 2006 and 2017 at two tertiary urogynaecological centres. Patients underwent a standardised interview, clinical examination and 3D/4D translabial ultrasound. Volume datasets were analysed by the second author, blinded against all clinical data, using post‐processing software on a personal computer. Significant prolapse was defined as Pelvic Organ Prolapse Quantification system stage ≥2 for the anterior and posterior compartment, and stage ≥1 for the central compartment. On imaging, significant prolapse was defined as previously described.

Results

Of 4297 women seen during the inclusion period, 409 were vaginally nulliparous, for whom 368 volume data sets could be retrieved. Mean age was 50 years (17–89) and mean body mass index 29 (16–64). Eighty‐one (22%) presented with prolapse symptoms. On clinical examination, 106 women (29%) had significant prolapse, mostly of the posterior compartment (n = 70, 19%). On imaging 64 women showed evidence of significant prolapse (17%), again mostly posterior (n = 47, 13%). Rectovaginal septal defects were even more common in 69 (19%). On multivariate analysis we found no differences between true nulliparae (n = 184) and women delivered exclusively by caesarean section (n = 184).

Conclusions

Prolapse occurs in vaginal nulliparae, but it has distinct characteristics. Rectocele predominates, while cystocele and uterine prolapse are uncommon. Pregnancy and caesarean delivery seem to have little effect.

Pelvic floor dysfunction at transperineal ultrasound and chronic constipation in women with endometriosis

OBJECTIVE

To assess the association between sonographic findings at transperineal ultrasound (TPU) and chronic constipation (CC) in women with endometriosis.

METHODS

An observational prospective cohort study was performed by enrolling all endometriosis women scheduled for surgery between September 2019 and October 2020. Women underwent TPU at rest and during Valsalva maneuver evaluating levator-hiatal-area (LHA), antero-posterior diameter (APD), levator-ani muscle (LAM)-coactivation. Ultrasound findings were compared between women with and without CC in the whole study population, and subsequently in two subgroups [only ovarian and deep infiltrating endometriosis (DIE)].

RESULTS

87 women were enrolled: 29 (33%) with CC and 58 (67%) without CC. Women with endometriosis and CC showed a smaller LHA during Valsalva, less LHA and APD enlargement from rest to maximum Valsalva, a higher prevalence of LAM-coactivation compared to women without CC. In ovarian-subgroup, women with CC had smaller LHA at Valsalva, less enlargement of LHA and APD from rest to maximum Valsalva and higher prevalence of LAM-coactivation compared to non-CC patients. In DIE-subgroup, TPU did not significantly differ between CC and non-CC patients.

CONCLUSION

TPU signs of pelvic floor muscle hypertone are more frequent in endometriosis patients with CC compared to those without constipation, particularly in women affected by isolated ovarian endometriosis.

A systematic review of diagnostic tests to detect pelvic floor myofascial pain

INTRODUCTION AND HYPOTHESIS

Myofascial pain arising from pelvic floor muscles occurs in women with vaginismus, interstitial cystitis and endometriosis but is often overlooked. The aim is to examine alternative diagnostic tests to detect pelvic floor myofascial pain compared with standardized vaginal palpation of pelvic floor muscles as the reference test.

METHODS

A systematic review was prospectively conducted (PROSPERO-CRD42020183092) according to PRISMA guidelines. Databases searched included Ovid Medline 1946-, Embase 1957-, Scopus 1960-, Cochrane Combined, Clinical trials, Google Scholar (top 200 articles), Web of Science, TRIP, BIOSIS, DARE, CINHAL, EmCare, PEDro, ProQuest and EBSCOhost up to July 2020. Articles were independently screened by two authors and assessed for bias using QUASDAS-2 tool.

RESULTS

A total of 26,778 articles were screened and 177 were selected for full text review, of which 5 were selected for final analysis. Five studies included 9694 participants of which 1628 had pelvic floor myofascial pain. Only one study reported data to calculate sensitivities and specificities of the index test, which utilized a score of > 40 on the Central Sensitization Inventory to detect women with pelvic floor myofascial pain and revealed a sensitivity of 34.8% and a specificity of 84.9% compared to the reference test.

CONCLUSIONS

This systematic review did not reveal any diagnostic test superior to the pre-defined reference test. There is a lack of consensus on the definition of pelvic floor myofascial pain and a lack of a validated diagnostic criteria which must be addressed to progress with meaningful research in this field.

Four-dimensional ultrasound biometry following botulinum toxin type A injection to the pelvic floor

AIMS

The objective of this study was to provide follow-up data on four-dimensional ultrasound (4DUS) morphometry for women having botulinum toxin type A (BoNT-A) treatment of pelvic floor tension myalgia (PFTM).

MATERIALS AND METHODS

A prospective cohort study was performed from October 2013 to June 2018, recruiting women scheduled for BoNT-A injection in the pelvic floor musculature. Translabial 4DUS, vaginal pressure assessment by manometry and pain visual analog scales (VAS) were performed on all women before injection and again at 4, 12, and 26 weeks. The BoNT-A injection was performed under 4DUS guidance.

RESULTS

Twenty-nine women had 44 injections over the course of the study. Although improvements were seen in VAS scores for dysmenorrhea, nonmenstrual pelvic pain, and dyspareunia, there were no significant differences in ultrasound biometry at either rest, Valsalva, or on contraction when comparing postinjection measurements at 4, 12, and 26 weeks with pre-injection baseline. Similarly, vaginal pressure readings at rest demonstrated a significant improvement throughout the 4, 12, and 26 week follow-up, with a reduction in maximal contraction at 4 and 12 but not 26 weeks.

CONCLUSIONS

This study demonstrates that 4DUS biometry of the pelvic floor does not correlate with clinical pain and vaginal pressure outcomes for BoNT-A injection in the context of PFTM.

The maternal pelvic floor and labor outcome

Vaginal birth is the major cause of pelvic floor damage. The development of transperineal ultrasound has improved our understanding of the relationship between vaginal birth and pelvic floor dysfunction. The female pelvic floor dimensions and function can be assessed reliably in pregnant women. Maternal pushing associated with pelvic floor muscle relaxation is the central requirement of vaginal birth. Many studies have evaluated the role of the pelvic floor on labor outcomes. Smaller levator hiatal dimensions and incomplete or absent levator ani muscle relaxation seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Here, we presented an overview of the current knowledge of the correlation between female pelvic floor dimension and function, as assessed by transperineal ultrasound, and labor outcome.

Transperineal ultrasound assessment of maternal pelvic floor at term and fetal head engagement

OBJECTIVES

To evaluate the association between pelvic floor dimensions in nulliparous women at term and fetal head engagement, as assessed by transperineal ultrasound.

METHODS

This was a prospective observational study of nulliparous women at term. Before the onset of labor, transperineal ultrasound was used to measure the anteroposterior diameter (APD) of the levator hiatus and the angle of progression (AoP) at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver (before and after visual feedback). We assessed the correlation between pelvic floor static and dynamic dimensions (levator hiatal APD and levator ani muscle coactivation) and AoP, which is an objective index of fetal head engagement.

RESULTS

In total, 282 women were included in the analysis. Among these, 211 (74.8%) women had a vaginal delivery while 71 (25.2%) had a Cesarean delivery. AoP was narrower in the Cesarean-delivery group at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva, whereas no differences in levator hiatal APD were found between the two groups. We found a negative correlation between levator hiatal APD at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva and the duration of the second stage of labor. There was a positive correlation between AoP and levator hiatal APD on maximum Valsalva maneuver after visual feedback (r = 0.15, P = 0.01). Women with levator ani muscle contraction on Valsalva maneuver (i.e. coactivation), both pre and post visual feedback, had a narrower AoP at rest and on maximum Valsalva. After visual feedback, women with levator ani muscle coactivation had a longer second stage of labor than did those without (80.8 ± 61.4 min vs 62.9 ± 43.4 min (P = 0.04)).

CONCLUSIONS

Smaller pelvic floor dimensions and levator ani muscle coactivation are associated with higher fetal head station and with a longer second stage of labor in nulliparous women at term. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

The dynamic change of the anteroposterior diameter of the levator hiatus under Valsalva maneuver at term and labor outcome

AIM

The aim of the present study was to evaluate the correlation between the proportional change of anteroposterior diameter (APD) of levator hiatus from rest to maximum Valsalva maneuver in nulliparous women at term and labor outcome.

METHODS

We prospectively recruited nulliparous women at term before the onset of labor. Women underwent a two-dimensional transperineal ultrasound, measuring the APD of the levator hiatus at rest and under maximum Valsalva's maneuver. APD change from rest to maximum Valsalva was described both in terms of absolute figures and proportional change. Correlation of APD change with the mode of delivery and with labor durations was assessed.

RESULTS

Overall, 486 women were included in the analysis. No significant association between change in APD and the mode of delivery. We found a significant negative correlation between change of APD from rest to Valsalva and the duration of active second stage both in terms of absolute change (Pearson's r = -0.138, P = .009) and in terms of proportional change (Pearson's r = -0.154, P = .004). Survival outcomes based on Cox-regression model showed that APD was independently associated with the duration of active second stage of labor after adjusting for epidural analgesia, maternal age and body mass index (hazard ratio, 1.008; 95% confidence interval, 1.001-1.016; P = .04) CONCLUSION: Women with higher increase of the anteroposterior diameter of the levator hiatus from rest to Valsalva have a shorter active second stage of labor.

Malmström vacuum or Kielland forceps: which causes more damage to pelvic floor?

OBJECTIVE

To determine whether differences exist in the rate of levator ani muscle (LAM) avulsion between women who had undergone either Malmström vacuum delivery (MVD) or Kielland forceps delivery (KFD), allowing for potential confounding factors.

METHODS

This was a prospective observational study of nulliparous women undergoing instrumental delivery using Malmström vacuum extractor or Kielland forceps, at two hospital centers in Spain. Fetal head position (anterior, posterior or transverse) and fetal head station (low or mid) were assessed by ultrasound and digital examination, respectively. Avulsion was defined on tomographic ultrasound imaging as an abnormal insertion of the LAM in the three central slices from the plane of minimal hiatal dimensions.

RESULTS

In total, 414 patients were included in the study (212 MVD and 202 KFD). We observed a higher rate of LAM avulsion in the KFD group (KFD 49.5% vs MVD 32.5%; P = 0.001). When the results were evaluated according to fetal head position and station, we observed no differences in LAM avulsion. The crude odds ratio (OR) for the difference in avulsion between women in the KFD and MVD groups was 2.03 (95% CI, 1.36-3.03). However, when adjusted for duration of second stage of labor, fetal head circumference and fetal head station, the OR was no longer statistically significant (OR, 2.14 (95% CI, 0.95-4.85); P = 0.068).

CONCLUSION

When potential confounding factors are taken into account, the rate of LAM avulsion does not differ between women according to whether they have undergone KFD or MVD. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Prevalence of levator hiatal overdistension after vacuum and forceps deliveries

INTRODUCTION

Levator ani avulsion rates after assisted vaginal delivery have been reported in the literature. However, there are no definitive data regarding the association between overdistention and assisted vaginal delivery. Therefore, our aim is to report overdistention rates after assisted vaginal delivery with a postpartum ultrasound examination.

MATERIALS AND METHODS

This multicenter study involved a retrospective analysis of data from primiparous women (n = 602) who had previously been recruited at three tertiary hospitals between January 2015 and January 2017. Overdistention was assessed at 6 months postpartum using three-/four-dimensional transperineal ultrasound. Patients with levator ani muscle avulsion were excluded. Overdistention was defined as a levator hiatal area ≥ 25 cm² on Valsalva.

RESULTS

Of the 602 primiparous patients, 250 patients who satisfied the inclusion criteria (139 patients who underwent forceps delivery and 111 patients who underwent vacuum delivery) were evaluated. Overdistention occurred in 20% (50 of 250) of these patients. Overdistention was observed for 1% (1/111) of vacuum deliveries and 35.3% (49 of 139) of forceps deliveries. We found an increased risk of overdistention following forceps delivery compared to vacuum delivery, with a crude odds ratio (OR) of 59.9 (95% confidence interval [CI]: 8.1, 442.2) and an adjusted OR (adjusted for maternal age, second-stage duration, and head circumference) of 17.6 (95% CI: 2.3, 136.7).

CONCLUSIONS

Postpartum overdistention occurred for 20% of assisted vaginal deliveries, with an increased risk of overdistention following forceps delivery compared to vacuum delivery.