Background Chorionic villus sampling (CVS) is the method of choice for prenatal diagnosis (PND) in first-trimester pregnancies (10–13thweeks and 6 days), particularly for high risk of fetal abnormalities. This procedure allows earlier diagnosis in order to enable effective pregnancy management. Microarray analysis is now performed on CVS.

Objectives/method We review 3 cases using fluorescence in situ hybridization on uncultivated nuclei (iFISH), CGH array results on DNA extraction from the entire villi and karyotype analyses on cultured CVS.

Results Two cases showed normal iFISH profile for chromosomes 13, 18, 21, X and Y, while the CGH array revealed a weak mosaicism for monosomy X in one CVS case and for trisomy 18 in the other. Karyotypes showed 45, X and 47, XY, +18 in more than 95% of the cells. In the third case, the iFISH and the CGH array were normal, but the karyotype revealed a trisomy 9 in 76% of the cells.

Conclusions CVS mosaicism and feto-placental discrepancies are rare phenomena occurring in ~1–2% of the PND. Cytogenetic analysis of CVS may give different results since CVS is from various placental cell lineages. Therefore, a cultured CVS (mesenchyme) analysis should be completed in order to reduce the incidence of false-positive or false-negative findings. In those cases, amniocentesis follow-up could be offered to complete the prenatal diagnosis.