One of the most common reasons for the lack of embryo implantation, frozen pregnancies in the early stages, as well as the birth of children with genetic pathologies are chromosomal aberrations.
A normal embryo has 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes, of which the X chromosome determines the female and the Y chromosome determines the male sex. The formation of an irregular number of chromosomes is called aneuploidy: the absence of one of the chromosomes is monosomy, the presence of an extra chromosome is trisomy.
The egg and sperm contain a haploid set of chromosomes – that is one chromosome from 23 pairs. At the same time, aneuploidies can occur both in the egg and sperm, and in the embryo itself after fertilization.
Timely detection of aneuploidies allows future parents to get a long-awaited pregnancy and avoid possible problems with the child’s health in the future. For this purpose, Preimplantation Genetic Screening is carried out in many IVF centers (PGS). It allows you to select embryos with a balanced set of chromosomes.
The effectiveness of PGS depends on the technique used. Thus, the method of fluorescent hybridizationи (FISH) allows you to analyze several chromosomes, while array-CGH – all 23 chromosomes. These methods are suitable for detecting chromosomal abnormalities, such as chromosome 21 trisomy (Down Syndrome), deletions and duplications, but are not able to detect mutations of individual genes.
Gene mutations can cause the birth of a child with such monogenic diseases as cystic fibrosis, spinal muscular atrophy, Fanconi anemia, Gaucher disease, Hemophilia B and many others. These diseases do not always manifest themselves in generations and therefore can be missed without a preliminary analysis of a specific gene.
A new generation sequencing method is a revolutionary technology for analyzing genetic information (NGS). This method is safe for the embryo, as it involves a biopsy on the fifth day of its development, when the embryo contains a large number of cells and the study is carried out on the trophectoderm. At the same time, it is possible to combine the study of chromosomal aberrations and monogenic diseases in one analysis. High accuracy of NGS allows to avoid false positive and false negative results in 99.9% of cases.
Our clinic offers all methods of preimplantation genetic screening.
When can you be recommended to conduct PGS:
- The age of the expectant mother is over 35 years old
- Habitual miscarriage of pregnancy, especially in the early stages
- Multiple failed IVF attempts
- Revealed chromosomal aberrations in previous pregnancies
- Chromosomal rearrangements or genetic diseases/carriers in a couple.
