Original Article

International Urogynecology Journal

, Volume 21, Issue 10, pp 1231-1236

First online:

Extraordinary muscular structure leads to urethral injury after vaginal delivery in animal study

  • Hung-Yen ChinAffiliated withMedical School, Chang Gung UniversityDepartment of Obstetrics and Gynecology, Chang Gung Memorial Hospital Email author 
  • , Eileen ChangchienAffiliated withR & D, Standard Chemical and Pharmaceutical. Co., Ltd
  • , Chi-Hsin ChiangAffiliated withDepartment of Obstetrics and Gynecology, Chang Gung Memorial Hospital
  • , Hsiu-Ping YangAffiliated withDepartment of Obstetrics and Gynecology, Chang Gung Memorial Hospital

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Introduction and hypothesis

The aim of this study is to explore causality of birth trauma after vaginal delivery and anatomical findings.


A total of 28 virgin mice were studied. Treatment groups received vaginal distention. Specimens were collected and subjected to the following fluorescence stains: progenitor cell (c-kit), smooth muscle (SMA), fibroblast (vimentin), and skeleton muscle (Masson’s trichrome). Confocal microscopy was used to screen all of the urogenital tissue to localize the stained cells.


Fibroblasts were spread all over perivaginal and urethral surroundings. Progenitor cells appeared at urethral–vagina intersection and urethral circle. They were noticeable only within smooth muscle layer. Two extraordinary skeleton muscle bands appeared on the urethra bilaterally.


Our study demonstrates existence of muscle bands at the bilateral urethra. They can limit the mobility of urethra during vaginal delivery and thereby cause urethra injury. Progenitor cells are located only in the smooth muscle of the urethral circle.


Birth trauma Fibrosis Stem cells Urethral injury Urinary incontinence Urogenital structure