Pelvic organ prolapse as a function of levator ani avulsion, hiatus size, and strength
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Background Obstetrical levator ani muscle avulsion is detected after 10%-30% of vaginal deliveries and is associated with pelvic organ prolapse later in life. However, the mechanism by which levator avulsion may contribute to prolapse is unknown.Objectives This study investigated the extent by which size of the levator hiatus and pelvic muscle weakness may explain the association between levator avulsion and pelvic organ prolapse.Study design This was a supplementary study of a longitudinal cohort of parous women enrolled 5-10 years after first delivery and assessed annually for prolapse (defined as descent beyond the hymen) for up to 9 annual visits. For this substudy, vaginally parous participants were assessed for levator avulsion using 3-dimensional transperineal ultrasound. Ultrasound was performed at a median interval of 11 years from delivery. Ultrasound volumes also were used to measure levator hiatus area with Valsalva. Pelvic muscle strength was measured with perineometry. Women with and without pelvic organ prolapse were compared for levator avulsion, levator hiatus area, and pelvic muscle strength, using multivariable logistic regression yielding a measure of mediation. Bootstrap methods were used to calculate the confidence interval corresponding to the measure of mediation by hiatus area and pelvic muscle strength.Results Prolapse was identified in 109 of 429 (25%) and was significantly associated with levator avulsion (odds ratio, 4.17; 95% confidence interval, 2.28-7.31). Prolapse also was associated with levator hiatus area (odds ratio, 1.52 per 5 cm 2; 95% confidence interval, 1.34-1.73) and inversely with muscle strength (odds ratio, 0.87 per 5 cm H 2 O; 95% confidence interval, 0.81-0.94). In a multivariable logistic model including levator avulsion, levator hiatus area, and strength, the association between levator avulsion and prolapse was substantially attenuated and indeed was no longer statistically significant (odds ratio, 1.75; 95% confidence interval, 0.91-3.39). Hiatus area and strength mediated 61% (95% confidence interval, 34%-106%) of the association between avulsion and prolapse. Furthermore, since the 95% confidence interval for this estimate contained 100%, it cannot be ruled out that the 2 markers fully mediate the effect of avulsion on prolapse.Conclusions The strong association between pelvic organ prolapse and levator avulsion can be explained to a large extent by a larger levator hiatus and weaker pelvic muscles after levator avulsion.
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The levator hiatus is the missing link between levator ani muscle avulsion and pelvic organ prolapse and is a principal etiological factor in the development of pelvic floor disorders.
“Besides, the levator hiatus, which was found to be the missing link between LAM avulsion and pelvic organ prolapse,13 was also the principal etiological factor in the development of PFD.14”
From Association Between Mode of Delivery and Levator Ani Muscle Abnormalities on 4D Transperineal Ultrasound at 6 Weeks Postpartum (2026) · cites this paper as [13]
Citation 13 attaches to the claim that the levator hiatus is the link between muscle avulsion and prolapse; the separate claim about pelvic floor disorders is attached to citation 14. The Conclusions and Comment say increased hiatus size may explain much of the association, but they also identify reduced muscle strength and present the mechanism as a hypothesis rather than an established single link. (LLM, conf=0.88)
Experimental — accuracy not yet measuredWe evaluated POP-Q point GH as a possible risk factor instead of levator defect because previous studies indicated an association between levator defect and genital hiatus size.
“Instead of levator defect, we evaluated POP-Q point GH as possible risk factor because previous studies indicated an association between levator defect and genital hiatus size.31”
From Risk factors for pelvic organ prolapse recurrence after sacrospinous hysteropexy or vaginal hysterectomy with uterosacral ligament suspension (2022) · cites this paper as [31]
The Materials and Methods section (page unavailable) reports that prior work in this cohort associated levator avulsion with a significantly larger levator hiatus. That supports an association between levator defect and hiatus size, but the paper measures levator hiatus area, not the POP-Q genital hiatus point GH named in the citing sentence. (LLM, conf=0.87)
Experimental — accuracy not yet measuredWomen with POP have pelvic floor muscle impairment.
“Women with POP have shown to have PFM impairment [4, 6, 8–16]”
From International urogynecology consultation chapter 3 committee 2; conservative treatment of patient with pelvic organ prolapse: Pelvic floor muscle training (2022) · cites this paper as [15]
For every 5-cmH2O increase in pressure during maximal voluntary contraction, the odds for prolapse was reduced by 13% (OR 0.87, 95% CI 0.81, 0.94).
“for every 5-cmH2O increase in pressure during maximal voluntary contraction, the odds for prolapse was reduced by 13% (OR 0.87, 95% CI 0.81, 0.94) [15].”
From International urogynecology consultation chapter 3 committee 2; conservative treatment of patient with pelvic organ prolapse: Pelvic floor muscle training (2022) · cites this paper as [15]
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- Authors
- Handa, V. L., Roem, J., Blomquist, J. L., Dietz, H. P., & Muñoz, A.
- Affiliations
- Johns Hopkins University (US)
- Greater Baltimore Medical Center (US)
- The University of Sydney (AU)
- Corresponding author
- Handa, Victoria L.
- Venue
- American Journal of Obstetrics and Gynecology
- Publisher
- Elsevier BV
- Published
- 2019-07
- Volume
- 221
- Issue
- 1
- Pages
- 41.e1-41.e7
- ISSN
- 0002-9378 (ISSN-L)
- PMC
- PMC6592735
- OpenAlex
- W2922125351
- Cited by
- 99
- References
- 22
- Citations by year
- 2026: 17 · 2025: 17 · 2024: 14 · 2023: 15 · 2022: 14 · 2021: 13 · 2020: 7 · 2019: 2
- FWCI
- 6.82
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- American Journal of Obstetrics and Gynecology (publishedVersion)
- PubMed (publishedVersion)
- PubMed Central (acceptedVersion)
- Funders
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD082070, R01HD056275)
- Topics
- Health Sciences › Medicine › Rheumatology › Pelvic floor disorders treatments
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Pregnancy-related medical research
- Health Sciences › Medicine › Psychiatry and Mental health › Sexual function and dysfunction studies
- Keywords
- pelvic organ prolapse, levator ani avulsion, levator hiatus, perineometry, transperineal ultrasound, mediation analysis, vaginal delivery, parous women
- MeSH terms
- Adult, Extraction, Obstetrical, Female, Humans, Longitudinal Studies, Middle Aged, Ultrasonography, Valsalva Maneuver, Cohort Studies, Multivariate Analysis, Logistic Models, Pelvic Floor, Imaging, Three-Dimensional, Delivery, Obstetric, Muscle Strength, Pelvic Organ Prolapse
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