a-CGH

a-CGH (Comparative Chromosome Screening)
It is a current method that detects changes in the amount of DNA. While a limited number of chromosomes can be scanned with PGD (FISH method), which is a genetic screening method that has been used for a long time in IVF applications, 24 chromosomes can be scanned with the a-CGH method. This method is based on scanning the whole gene with Oligonucleotide \ BAC array.

With the a-CGH method, possible abnormalities in chromosomes can be detected due to duplications (increase), deletions (loss) and translocation (replacement) carriers on chromosomes. While it allows the detection of both maternal and paternal abnormalities, it also enables the screening of single gene diseases.

a-CGH advantages;
• Patients' repeated unsuccessful IVF attempts are prevented.
• Since this technique allows scanning of all chromosomes (22 XY), its reliability is higher than the FISH method.
• It is less risky in terms of monosomy and other complicated numerical chromosomal disorders (aneuploidy), and since more cells can be examined, it provides a healthier analysis opportunity compared to third-day embryo biopsy.
• The rate of mosaicism in the blastocyst is lower than that of the third day embryo, providing a more reliable analysis.

NGS (Next Generation Sequencing)

With this method, structural and numerical anomalies on chromosomes can be detected with a computerized system by comparing with a second DNA known to be normal after DNA amplification. The sequences of DNA fragments that have undergone various processes are read separately for each embryo and evaluated with a special algorithm.

The advantages of the NGS method over the a-CGH method are as follows;

• Since it is a direct analysis method, it is a technique that works with a higher sensitivity.

• While the detection rate of mosaic embryos with a-CGH is 5%, this rate is between 15-30% with NGS (12% mosaicism can be observed even in embryos reaching the blastocyst).

• 'Normal' embryos defined by NGS have a lower abortion rate than other PGS methods.

• Higher implantation (clinical pregnancy) rates are obtained compared to the a-CGH method.

As a result, with the use of the aforementioned genetic screening methods, selective embryo transfer is provided and pregnancy rates are significantly increased.
Finally, do not forget that the determination of which of these methods is right for you will be done by the IVF team.