title: De novo small supernumerary marker chromosomes detected on 143,000 consecutive prenatal diagnoses: chromosomal distribution, frequencies, and characterization combining molecular cytogenetics approaches.
abstract: OBJECTIVE
  The risk of clinical consequences in prenatal cases with de novo small supernumerary marker chromosomes (sSMC), often in mosaic conditions, is not easy to predict, which results in difficulties in genetic counseling.
  
  
  METHODS
  In this study, we evaluated the frequency, the chromosomal origin, and the clinical indication of 104 de novo sSMC detected in a monocenter survey on the basis of 143,000 consecutive prenatal diagnoses, and we assessed the reliability of molecular cytogenetics technologies for sSMC characterization.
  
  
  RESULTS
  We detected a de novo sSMC frequency of 0.072%. Its incidence in advanced maternal age group is statistically different from that found in maternal anxiety indication (<35 years old). A higher prevalence of mosaicism in chorionic villi sampling (CVS) than in amniotic fluids was also revealed related to confined placental mosaicisms. The risk of confirmation in amniotic fluids of mosaics previously revealed at CVS was 33.3%. No uniparental disomy conditions were found when imprinted chromosomes were involved in the occurrence of de novo sSMC. The majority of de novo sSMC were acrocentric derived-chromosomes, and a neocentromere formation was observed in one pregnancy.
  
  
  CONCLUSIONS
  Our data support that array comparative genomic hybridization has improved sSMC characterization and demonstrate its utility in supporting genetic counseling. We propose a workflow for de novo sSMC characterization.
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays, Busto Arsizio, Varese, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Malvestiti
authors.forename: Simona
authors.initials: S
authors.lastname: De Toffol
authors.forename: Beatrice
authors.initials: B
authors.lastname: Grimi
authors.forename: Sara
authors.initials: S
authors.lastname: Chinetti
authors.forename: Livia
authors.initials: L
authors.lastname: Marcato
authors.forename: Cristina
authors.initials: C
authors.lastname: Agrati
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Di Meco
authors.forename: Giuditta
authors.initials: G
authors.lastname: Frascoli
authors.forename: Anna
authors.initials: A
authors.lastname: Trotta
authors.forename: Barbara
authors.initials: B
authors.lastname: Malvestiti
authors.forename: Anna
authors.initials: A
authors.lastname: Ruggeri
authors.forename: Francesca
authors.initials: F
authors.lastname: Dulcetti
authors.forename: Federico
authors.initials: F
authors.lastname: Maggi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Simoni
authors.forename: Francesca Romana
authors.initials: FR
authors.lastname: Grati
mesh_terms: D000328:Adult; D002869:Chromosome Aberrations / Q000706:statistics & numerical data*; D002875:Chromosomes; D055028:Comparative Genomic Hybridization / Q000379:methods / Q000706:statistics & numerical data; D020732:Cytogenetic Analysis / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D005819:Genetic Markers; D006801:Humans; D015994:Incidence; D008297:Male; D009030:Mosaicism / Q000706:statistics & numerical data*; D011247:Pregnancy; D011296:Prenatal Diagnosis; D015203:Reproducibility of Results
chemical_list: D005819:Genetic Markers