CCS is a diagnostic test to determine if the embryo is “normal” or not prior to embryo transfer. It is done independently of the traditional embryo selection methods and Eeva™.
In order to do CCS, the eggs are fertilized and the fertilized eggs are grown to the day 5/6 stage of embryo development (blastocyst). If the embryos do not develop to the blastocyst stage, CCS cannot be done. Some embryos survive to day 5 but do not form blastocysts. Embryos that do not make blastocysts by day 6 are presumed not to be “normal”.
At the blastocyst stage (day 5 or 6 post fertilization), the embryos are biopsied. The biopsy removes 5-7 cells from the layer of cells that will become the placenta (trophectoderm). The cells that will become the fetus are undisturbed. The embryos are frozen and the biopsy sent to a genetics lab for analysis.
The analysis determines if the chromosomal complement is “balanced” or “normal” or “viable”. The certainty of this diagnosis is greater than 98%. CCS does not assess single genes that sit on the chromosomes (for example: cystic fibrosis or thalassemia. Single Gene Diagnosis is accomplished by another technique called Pre-implantation Genetic Diagnosis (PGD).
The most common reason that embryos do not implant or later miscarry is that they were not chromosomally normal. Rarely, unbalanced embryos will continue to term.
The most common reason that an embryo is not normal is egg age (ie maternal age) which leads to failed accurate separation of chromosomes during the cell division process (nondisjunction). This leads to an imbalance (too much or too little) of chromosomal DNA material in the embryo.
When “normal” embryos are identified, the patient will return for a frozen embryo transfer. When a single “normal” embryo is transferred, the pregnancy rates are maximized and miscarriage rates minimized. Excellent IVF success rates are achieved independently of maternal age if the embryo is known to be “normal”. i.e. a 40 year old woman who transfers a known “ normal “ embryo will have the same pregnancy rate at a 30 year old woman who transfers a known “ normal” embryo.
Any patient who is doing IVF may benefit from CCS but CCS is most cost effective in patients who have:
- recurrent pregnancy loss
- age > 36 with good ovarian reserve
- repeated implantation failure
- multiple failed IVF cycles