title: Preimplantation genetic screening reveals a high incidence of aneuploidy and mosaicism in embryos from young women undergoing IVF.
abstract: BACKGROUND
  In order to assess the frequency of aneuploidy and mosaicism in embryos obtained from IVF patients aged <38 years, preimplantation genetic screening (PGS) was performed after biopsy of two blastomeres. Furthermore, the reliability of this diagnosis was assessed by performing reanalysis of the embryo on day 5.
  
  
  METHODS
  The copy numbers of 10 chromosomes (1, 7, 13, 15, 16, 18, 21, 22, X and Y) were investigated by fluorescence in situ hybridization (FISH) analysis. Embryos that were found to be abnormal or of insufficient morphological quality were cultured until day 5 and reanalysed. Results obtained were compared to the day 3 blastomere analysis.
  
  
  RESULTS
  After analysis of 196 embryos (one cell in 38% and two cells in 62%), only 36% of the embryos were found to be normal on day 3. After analysis of two blastomeres, 50% showed chromosomal mosaicism. Comparison of the FISH results from day 3 blastomeres and day 5 embryos yielded an overall cytogenetic confirmation rate of 54%.
  
  
  CONCLUSIONS
  The rates of mosaicism and aneuploidy in these embryos from young IVF patients are similar to those published for older women. We found the best confirmation rate after a diagnosis based on two cells, where both blastomeres showed the same chromosomal abnormality. In contrast, after a mosaic diagnosis the confirmation rate was low. The present study provides the first detailed reanalysis data of embryos analysed by PGS and clearly demonstrates the impact of mosaicism on the reliability of the PGS diagnosis.
authors.affiliation: Division of Reproductive Medicine, Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Center, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. e.baart@erasmusmc.nl
authors.forename: E B
authors.initials: EB
authors.lastname: Baart
authors.forename: E
authors.initials: E
authors.lastname: Martini
authors.forename: I
authors.initials: I
authors.lastname: van den Berg
authors.forename: N S
authors.initials: NS
authors.lastname: Macklon
authors.forename: R-J H
authors.initials: RJ
authors.lastname: Galjaard
authors.forename: B C J M
authors.initials: BC
authors.lastname: Fauser
authors.forename: D
authors.initials: D
authors.lastname: Van Opstal
mesh_terms: D000328:Adult; D000782:Aneuploidy; D025063:Chromosome Disorders / Q000175:diagnosis*; D020732:Cytogenetic Analysis; D004622:Embryo, Mammalian / Q000002:abnormalities*; D005260:Female; D005307:Fertilization in Vitro; D005820:Genetic Testing; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D009030:Mosaicism / Q000196:embryology*; D019836:Preimplantation Diagnosis