title: A Study of Myometrial Growth and Development.
abstract: OBJECTIVE
  To evaluate myometrial growth and development.
  
  
  METHODS
  Thirty-five autopsy uteri, ranging from 10 weeks' gestation to age 18 years, acquired over 3 decades from 2 hospitals, were studied based on specimen availability, photographed for documentation, and reviewed at the end of the study. Most were embedded in toto, with 1 block and 1 slide per case. Some were immunostained for actin, CD10, MIB-1, and/or trichrome stain for collagen and muscle. Myometrial thickness was measured by ocular micrometry when sections were nontangential and analyzed by paired-sample t tests and bivariate linear regression.
  
  
  METHODS
  Two university-affiliated hospitals.
  
  
  RESULTS
  From 20 to 34 weeks, lateral wall corpus thickness increased 6-fold, with a 4- to 6-fold perinatal burst of growth (P < .01) and a drop in thickness after the neonatal period (P = .013). The corpus was thicker than the dome (P < .01) but less thick than the lower uterine segment (P = .087). The lower uterine segment was fully muscular in the second trimester, becoming more fibrous near term. Intramural, subserosal, and inframucosal myometaplasia were observed, as primitive stromal cells turned into muscle cells. Myometrial proliferation was brisk in the second trimester but greatly diminished in the perinatal period. Pressure effects from myometrial tone were observed during development. There was a pubertal burst of inframucosal myometaplasia.
  
  
  CONCLUSIONS
  Myometaplasia accounted for most myometrial growth, especially in the perinatal and pubertal bursts of growth. Pressure effects, related to myometrial tone, appeared to affect myometrial development. True endocervix, with a fibrous wall and mucinous epithelium, appeared late in development.
authors.affiliation: Department of Pathology, Rochester General Hospital, University of Rochester School of Medicine, Rochester, New York.
authors.forename: Stewart F
authors.initials: SF
authors.lastname: Cramer
authors.affiliation: Department of Human Development and Family Science, The University of Georgia, Athens, Georgia.
authors.forename: Assaf
authors.initials: A
authors.lastname: Oshri
authors.affiliation: Department of Pathology, Rutgers-New Jersey Medical School, Newark, New Jersey. Electronic address: hellerds@njms.rutgers.edu.
authors.forename: Debra S
authors.initials: DS
authors.lastname: Heller
mesh_terms: D000293:Adolescent; D001344:Autopsy; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D009215:Myometrium / Q000254:growth & development*; D011247:Pregnancy
keywords: Development; Lower uterine segment; Myometaplasia; Myometrium