Preimplantation diagnostics of the embryo by ARRAY-CGH method

In theIVMEDclinic, preimplantation genetic diagnostics is performed using a modern method of comparative hybridization on microarrays (array comparative genome hybridization or array-CGH).

Array-CGH increases:

• the success of the IVF program;
• the probability of having a healthy baby.

Reduces:

• the risk of disruption of the embryo implantation process;
• the likelihood of developing embryogenesis pathologies;
• risk of pregnancy termination

Array-CGH is a method of simultaneously examining all chromosomes to determine their quantitative and qualitative abnormalities. Thanks to this study, it is possible to exclude the development of Down syndrome, Edwards syndrome, Shereshevsky-Turner syndrome, as well as a number of other chromosomal pathologies accompanied by physical defects and severe mental retardation in an unborn child.

Preimplantation genetic diagnostics using the Array-CGH method is performed at:

• older reproductive age of the spouses (for women 35 years and older, for men 40 years and older);
• male factor of infertility associated with spermatogenesis disorders;
• habitual miscarriage;
• repeated unsuccessful IVF attempts.

The study is recommended in cases of:

• at least one of the spouses has a chromosomal abnormality;
• having relatives with chromosomal diseases in the family;
• the presence of sexually transmitted diseases in the family history.

Advantages of ARRAY-CGH:

• 100% – screening of all 24 chromosomes of the embryo;
• 5 – the test is performed on the 5th day of embryo development;
• 0.07% – the volume of embryo cells required for the analysis eliminates risks for its further development;
• 70-84% – the probability of IVF success increases to 70-84% even with a single embryo transfer.

How is the preimplantation diagnosis of the embryo performed using the ARRAY-CGH method?

The study by comparative hybridization on microarrays is carried out as part of IVF programs on the 5th day of embryo cultivation, when it reaches the blastocyst stage. At this stage of development, the embryo consists of an outer layer of cells (trophectoderm) and an inner cell mass, which will form the organs and tissues of the fetus in the future.

The procedure for taking cells for genetic testing is called an embryo biopsy. Using micro instruments, the embryologist carefully takes up to 10 trophectoderm cells. After that, the embryos are vitrified (frozen) for the duration of the study.

The samples are sent to a genetic laboratory, where the array-CGH method is used. This method is based on comparing the test and control (normal) genomic samples.

Stages of comparative hybridization on microarrays:

1. The test and control samples are labeled with different color fluorochromes.
2. Mix the samples in a 1:1 ratio.
3. DNA is denatured to obtain a mass of single-stranded molecules.
4. The samples are recorded on DNA microarrays.
   DNA microarrays or DNA probes are a collection of many single-stranded bacterial DNA molecules standardized by nucleotide sequence and located on specific sites on the membrane backbone. Labeled genomic samples are complementarily bound (hybridized) to DNA microarray molecules.
5. A special technology is used to wash the microarray to remove molecules that remain unhybridized and to fix the bound DNA strands.
6. The instrument with an argon laser is used to scan samples to determine the number and location of fluorescent DNA molecules. The laser causes the marks to glow, and by analyzing the ratio of colors on the chip and their brightness, it is possible to detect duplications, a local increase in the number of repeats, or the loss of part of the genetic material.

The process of genetic diagnosis of the embryo by the array-CGH method is automated: the analysis is performed by computer programs, and the result is presented in electronic form. A geneticist interprets this test. Based on the results of the analysis, a genetically healthy embryo is selected, thawed, and after medical preparation, the patient undergoes an embryo transfer.

Diagnosis of the embryo using the array-CGH method allows you to analyze the entire genome and identify chromosomal abnormalities. Other PGD methods are used to detect mosaicism, local gene mutations, and monogenic diseases.

Take advantage of preimplantation embryo diagnostics using the array-CGH method at theIVMEDclinic to increase your chances of a successful pregnancy and the birth of your genetically healthy child.