Chromosome analysis in chorionic villi samples from the first trimester elective terminations

Area of Science:

• Genetics
• Prenatal Diagnosis
• Cytogenetics

Background:

• Chorionic villi sampling (CVS) is a first-trimester alternative to amniocentesis for prenatal diagnosis.
• Maternal age in the study cohort ranged from 12 to 35 years, with a concentration of mothers aged 18-19.
• Investigated parameters aimed to optimize CVS culturing and processing for cytogenetic analysis.

Purpose of the Study:

• To present cytogenetic findings from 150 chorionic villi sampling (CVS) procedures.
• To evaluate the accuracy and reliability of CVS for prenatal genetic diagnosis.
• To identify and discuss discrepancies between CVS and fetal tissue cytogenetics.

Main Methods:

• Routine cytogenetic analysis of CVS samples using short-term incubation (48 hours).
• Comparison of karyotypes from CVS with corresponding fetal tissues in a subset of cases.
• Assessment for maternal contamination in CVS samples.

Main Results:

• In the first 100 cases, abnormalities included one mosaic case (46,XX/45,X), one Robertsonian translocation (13;14), one marker chromosome, and one fragment.
• In the second series of 50 samples, one case of confined placental mosaicism (46,XX/47,XX, 18q-) was detected in chorionic villi but not in fetal tissue.
• One variant inv(9) was consistently found in both CVS and fetal tissues.
• No maternal contamination was detected in the 50-sample series.
• Overall, karyotypes from CVS samples matched fetal samples in the majority of cases.

Conclusions:

• CVS is a valuable first-trimester prenatal diagnostic tool.
• While generally accurate, rare instances of mosaicism and discrepancies between CVS and fetal tissue require careful interpretation.
• Further investigation into discrepancies observed compared to other studies is warranted.