Chromosome Analysis, Chorionic villus Test

Prenatal chromosome analysis on chorionic villi is instructed to to do when individual is at increased risk for fetal aneuploidy based on maternal age, abnormal noninvasive prenatal testing, abnormal multiple marker screening, or abnormal fetal ultrasound. It is also instructed to do in people who have a family history of chromosome abnormality or genetic disorder.

Chorionic villi consist of an outer layer of trophoblastic cells and an inner mesenchymal cell core. They can be prepared for chromosome analysis using a culture method wherein villi are disaggregated by mechanical and enzymatic methods and the resulting cell suspension is used to establish primary cultures. Mesenchymal cells of the villus core are released by this procedure and the fibroblasts are actively proliferative in tissue culture. Cultures can be used for cytogenetic analysis after 1 week. Slides prepared by this technique can be stained using trypsin-Giemsa banding and analyzed for chromosomal abnormalities in fetal tissue.

• To determine fetal karyotype
• Prenatal diagnosis of chromosome abnormalities, including aneuploidy (ie, trisomy or monosomy) and balanced rearrangements

• 20 to 30mg of specimen Chorionic villi is needed for this test.
• The specimen is collected in syringe (transabdominal) or catheter (transcervical) and transferred by flushing with the media from the sterile container back into it.
• After collecting the specimen, wash with sterile saline solution containing sodium heparin.
• Carefully transfer the specimen, into the CVS transport tube, using a sterile Pasteur pipette or a sterile fine needle forceps. Be sure to fill transport tubes completely with media.
• Samples from twin (multiple) pregnancies should be appropriately labeled and placed in separate transport containers with a separate request form for each twin.