title: Number of germ cells and somatic cells in human fetal ovaries during the first weeks after sex differentiation.
abstract: BACKGROUND
  This study presents the number of germ cells and somatic cells in human fetal ovaries during week 6 to week 9 post conception, i.e. the first weeks following sex differentiation of the gonads.
  
  
  METHODS
  One ovary with attached mesonephros from each of 11 individual legal abortions was used for estimation of cell numbers. After recovery of the fetus, the ovary-mesonephric complexes were immediately isolated, fixed and processed for histology. A stereological method was utilized to estimate the total number of oogonia in all ovaries and somatic cells in seven of them.
  
  
  RESULTS
  The number of oogonia per ovary increased from approximately 26,000 in week 6 to approximately 250,000 in week 9 and somatic cells from approximately 240,000 to approximately 1.4 x 10(6). The ratio of oogonia to somatic cells tended to increase throughout the period. The concentration of oogonia was similar in the cranial (mesonephric connected) part and the caudal part of the ovaries.
  
  
  CONCLUSIONS
  This is the first stereological estimation of the number of oogonia and somatic cells in human fetal ovaries, and the first estimation of germ cells and somatic cells in ovaries aged <9 weeks. The number of oogonia in week 9 is comparable to the numbers previously published based on non-stereological estimations. We found early stages of meiosis in fetal ovaries from week 9.
authors.affiliation: Fertility Clinic, Department of Obstetrics and Gynaecology, University Hospital of Odense, Sdr. Boulevard 29, 5000 Odense C, Denmark. e.bendsen@dadlnet.dk
authors.forename: E
authors.initials: E
authors.lastname: Bendsen
authors.forename: A G
authors.initials: AG
authors.lastname: Byskov
authors.forename: C Yding
authors.initials: CY
authors.lastname: Andersen
authors.forename: L G
authors.initials: LG
authors.lastname: Westergaard
mesh_terms: D002452:Cell Count; D005260:Female; D005306:Fertilization; D005333:Fetus / Q000033:anatomy & histology*; D006801:Humans; D009867:Oogonia / Q000166:cytology*; D010053:Ovary / Q000166:cytology*; D011247:Pregnancy; D012733:Sex Differentiation