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Comprehensive Chromosomal Screening Explained
Comprehensive Chromosomal Screening (CCS) is a type of preimplantation genetic screening (PGS) done in an IVF cycle. CCS allows for the evaluation of all 23 pairs of chromosomes to determine if the embryo is euploid - has a correct number of chromosomes, or is aneuploid - has an incorrect number of chromosomes.
With CCS, 5 to 10 cells are retrieved from the trophectoderm of a blastocyst - a Day 5 or 6 embryo. The trophectoderm contains cells that will develop into the placenta, rather than the fetus. The embryo is frozen using a fast freeze technology called vitrification, while waiting for the result of the biopsy.
In a separate cycle, the normal embryo is thawed and transferred in a frozen embryo transfer. Single embryo transfer is usually encouraged due to high success rates with euploid embryos.
CCS may be recommended in an IVF cycle when:
- The women is over 35
- There have been previous IVF failures
- There is a history of recurrent miscarriage