title: Interpreting mosaicism in chorionic villi: results of a monocentric series of 1001 mosaics in chorionic villi with follow-up amniocentesis.
abstract: OBJECTIVE
  Chromosomal mosaicism in chorionic villi (CV) is detected in ~1-2% of cases. When a mosaic in CV is detected during prenatal diagnosis, a confirmatory karyotype should be performed on amniocytes to discriminate between a mosaic confined to the placenta [confined placental mosaicism (CPM)] and one generalized to the fetus [true fetal mosaicism (TFM)]. We determined the likelihood that any mosaic abnormalities identified through CV samples are confirmed in the fetus.
  
  
  METHODS
  Over a period of 14 years, the laboratory analyzed both the cytotrophoblast and the mesenchyme of 60 347 CV samples. Cytogenetic results from CV samples showing mosaicism with follow-up amniocentesis were considered. The incidence of CPM and TFM and the risk of confirmation in the amniotic fluid (AF) were calculated. Uniparental disomy (UPD) was tested on ~300 cases at risk due to involvement of an imprinted chromosome.
  
  
  RESULTS
  Overall, 1317 mosaic CV cases (2.18%) were detected, of which 1001 were subsequently investigated by amniocentesis. The overall risk of TFM was 13% and UPD incidence was 2.1%.
  
  
  CONCLUSIONS
  The very large presented sample set and consistency in cytogenetic methodology, especially the analysis of both placental layers performed on all CV samples will enable genetic counselors to determine the risk of fetal involvement and the clinical relevance of an identified mosaic condition.
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Malvestiti
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Agrati
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Grimi
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.|GYNEPRO, V.le Carducci, 2/3, Bologna, Italy.
authors.forename: Eva
authors.initials: E
authors.lastname: Pompilii
authors.affiliation: UO Diagnosi Prenatale, Azienda Ospedaliera Spedali Civili, Brescia, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Izzi
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Martinoni
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Gaetani
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Liuti
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Trotta
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Maggi
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Simoni
authors.affiliation: Research and Development, Cytogenetics and Molecular Biology, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, VA, Italy.
authors.forename: Francesca Romana
authors.initials: FR
authors.lastname: Grati
mesh_terms: D000649:Amniocentesis; D000653:Amniotic Fluid; D002824:Chorionic Villi / Q000378:metabolism*; D015193:Chorionic Villi Sampling; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D007621:Karyotyping; D008648:Mesoderm / Q000378:metabolism*; D009030:Mosaicism; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D014314:Trisomy / Q000175:diagnosis*; D014327:Trophoblasts / Q000378:metabolism*; D024182:Uniparental Disomy / Q000235:genetics*