[Effect of pregnancy and spontaneous delivery on the morphology of levator ani muscle and expression of vaginal nerve fibers].
OBJECTIVE
To investigate the effect of pregnancy and spontaneous delivery on the morphologic characteristics of the levator ani muscle and innervation of the vaginal mucosa.


METHODS
Eight nullipara without pelvic floor dysfunction (PFD) and 64 normal primipara undergoing spontaneous delivery were enrolled in this study during July to December 2006 in Peking Union Medical College Hospital. Biopsy specimens of levator ani muscle (LAM) and anterior and posterior vaginal walls were obtained from the puerpera as well as from the 8 nullipara undergoing vaginal operation. The structures of LAM were examined with histological techniques. Vaginal mucosa specimens were examined using immunohistochemistry staining for protein gene product 9.5 (PGP 9.5), vasoactive intestinal peptide (VIP) and ne uropeptide Y (NPY), and the positive stained nerve fibers were calculated respectively.


RESULTS
The LAMs of the puerpera undergoing spontaneous delivery presented myogenetic and neurogenetic changes, both acute and chronic. Type I muscular fibers were predominant (79%) with both types increasing in diameters [(86 +/- 9) microm and (79 +/- 15) microm]. Significantly different (P < 0.05) innervation of PGP 9.5, VIP, and NPY nerve fibers was observed between epithelial lamina of anterior vaginal wall (5.9 +/- 3.3, 7.6 +/- 3.1 and 8.2 +/- 3.2, respectively) and that of posterior vaginal wall (3.8 +/- 2.9, 5.9 +/- 3.1 and 6.0 +/- 3.0, respectively), with the nerve fibers being more in epithelial lamina of anterior vaginal wall, while no difference in the innervation of nerve fibers was observed in the lamina propria. Significantly different (P < 0.05) innervation of PGP 9.5 and VIP nerve fibers was observed in the lamina propria of the anterior vaginal wall in puerperal undergoing vaginal delivery (6.9 +/- 3.2 and 4.9 +/- 2.1) compared with those in nullipara (3.9 +/- 3.6 and 3.1 +/- 1.2).


CONCLUSIONS
Pathologic changes occur in LAMs and pelvic floor nerves during labor and delivery. LAM fibers become hypertrophy to adapt to the physiological changes during pregnancy. Richer innervation of PGP 9.5 and VIP nerve fibers in the lamina propria of the anterior vaginal wall in puerpera undergoing spontaneous delivery is beneficial for dilation of the blood vessels and smooth muscles and makes preparation for delivery.
Teng
Li-Rong
LR
Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China.
Bian
Xu-Ming
XM
Zhu
Lan
L
Lang
Jing-He
JH
Liu
Jun-Tao
JT
Yang
Jian-Qiu
JQ
Ren
Hai-Tao
HT
Zhao
Yan-Huan
YH
Chen
Lin
L
D000328:Adult; D001003:Anal Canal / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology*; D009321:Natural Childbirth; D009412:Nerve Fibers / Q000378:metabolism / Q000473:pathology; D017773:Pelvic Floor / Q000294:innervation* / Q000473:pathology; D011247:Pregnancy; D014621:Vagina / Q000294:innervation*; D055815:Young Adult