Chromosomal abnormalities in embryos may cause implantation failures and miscarriages
CGH technique which is the newest PGD technique which looks at all chromosomes of the embryos. Humans have 46 chromosomes. Therefore its a much more developed technique. Fisch technique PGD on the hand looks only at 5 chromosomes. CGH gives a better understanding of genetically healthy embryos compared to the Fish Technique
The disadvantage is that the CGH is priced per embryo and the analysis is still expensive. CGH is required the embryos to be frozen. We do the CGH and freeze the embryos 5-6 days after the egg collection. It takes about 2-3 weeks for the results to come. The patient needs to come back to the clinic for a frozen embryo transfer.
This technique is useful for couples who had multiple IVF failures or miscarriages.
Below you can see the report of 2 cases done with Array CGH. On the X-axis you see the chromosome numbers starting from 1 to 22 and then you see the X and Y chromosomes.
The first graphic shows the compatibility of an embryo sample to a normal female DNA. The second one shows the compatibility of the same embryo to a male DNA. This is done in such a way because we cannot know the gender of the embryos at the beginning. The red moving line shows anomalies at the 4th chromosome and therefore there is a blue box that lies above the red line. This indicates that chromosome 4 has extended itself and it causes Trisomy, meaning that chromosome 4 extended from being 2 DNAs to 3 DNAs. An embryo with 3 DNA of the same chromosome is considered abnormal.
At the end of the graph, we also see that the X chromosome is below the red line and Y chromosome is above the red line. This is however normal now because as mentioned, this is a compatibility test of an embryo to a female embryo that has XX chromosomes. The male embryo has XY chromosomes. This particular embryo is a male embryo because it has 1 less X chromosome and 1 extra chromosome of Y. In the second graph, we see the performance of the same embryo to a male DNA. There we still see the problem on Chromosome 4 but we don’t see a problem at the end of the Graph where the X and Y chromosomes are. Since it came normal we understand that this embryo is a male embryo.
On the third and fourth graphics, we see normal male embryo graphics. There is no chromosomal abnormality