Preimplantation Genetic Screening (PGS)
One of the most common causes of embryo implantation failure, miscarriages in early pregnancy and the birth of children with genetic abnormalities are chromosomal aberrations.
Normal embryo has 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes, of which the X-chromosome determines Female and the Y-chromosome – Male. Formation of the wrong number of chromosomes is called aneuploidy: absence of one of the chromosomes is called monosomy, the presence of an extra chromosome - trisomy.
Egg and sperm contain a haploid set of chromosomes - that is, on a single chromosome out of 23 couples. Thus, Aneuploidy may occur as in the egg and sperm, and the embryo after fertilization.
Timely detection of aneuploidies allows prospective parents to get a long-awaited pregnancy and avoid possible problems with the health of the child in the future. For this purpose, many IVF centers perform preimplantation genetic screening (PGS). It allows you to select embryos with a balanced set of chromosomes.
The efficiency depends on the PGS technique. Thus, fluorescence hybridization (FISH) allows analyzing several chromosomes, while the array-CGH - all 23 chromosomes. These methods are suitable for the detection of chromosomal abnormalities such as trisomy of chromosome 21 (Down Syndrome), deletions and duplications, but are not able to identify single gene mutations.
Mutations in gene single cause a newborn with monogenic diseases such as cystic fibrosis, spinal muscular atrophy, Fauconi anemia, Gaucher's disease, Hemophilia B and many others. Not always these diseases are seen in generations, and thus can be missed without prior analysis of a particular gene.
The Next Generation Sequencing (NGS) - is the revolutionary technology of genetic information analysis. This method is safe for the embryo, as it implies a biopsy on the fifth day of development when the embryo contains a large number of cells, and research is being conducted on trophectoderm. It allows combining the study of chromosomal aberrations and monogenic diseases in a single analysis. High accuracy NGS avoids false-positive and false-negative results in 99.9% of cases.
Our clinic offers all methods of Preimplantation Genetic Screening - PGD, PGS and NGS.
When you might be advised to hold PGS:
- Age of expectant mother over 35 years old
- Recurrent miscarriages, especially in the early pregnancy
- Multiple unsuccessful IVF attempts
- The identified chromosomal aberrations in the previous pregnancies
- Chromosomal alterations or genetic diseases / the carriage of the couple.