In the context of assisted reproduction techniques it is possible to perform genetic testing and selection of embryos created in a test tube before transfer to the uterus and implantation, thus in a preimplantation manner.
The method is based on the conclusions of genetic counseling. Preimplantation testing may either focus on diseases that are already present in the family or on random genetic changes caused by external environment or age of parents.
First a cell or several cells are withdrawn from the embryo - the so-called biopsy. It is carried out by an embryologist on the third or fifth day after the fertilization of the egg with sperm.
Embryo biopsy day 3
Chromosomes are examined in one cell (blastomere) of a three-day-old embryo. The result of the examination is available within 48 hours.
Embryo biopsy day 5
Chromosomes are examined in 3-5 cells of a five-day-old embryo (blastocyst). Embryos are frozen and in case of a normal result they are transferred in one of the future cycles. The result of the examination is usually available within 1 month.
We distinguish two basic types of preimplantation examination:
- PGD (preimplantation genetic diagnosis)
- targeted examination of embryos to exclude hereditary disease in the family, where one partner or both are carriers of predisposition of the specific disease
- PGS (preimplantation genetic screening)
- examination of embryos to exclude new emerging chromosomal defects in a couple without genetic disorders