Preimplantation genetic testing is a cutting-edge procedure performed in conjunction with in vitro fertilization in which a few cells extracted from the developing embryos are tested for genetic diseases. By analyzing the extracted DNA with specific tests, the doctor and embryologist can select embryos that do not carry a specific genetic disease or any chromosome abnormalities. The embryos subsequently undergo implantation and produce a genetically healthy pregnancy and decrease spontaneous miscarriage and birth defects.
There are two types of PGT that can be performed
- Preimplantation Genetic Screening (PGS)
Parents have no known genetic abnormalities and their embryos are screened for chromosomal abnormalities (aneuploidy).
- Preimplantation Genetic Diagnosis (PGD)
Parent(s) carry a genetic condition and testing is performed to determine whether that condition has been transmitted to the embryos.
How it works?
PGS/PGD requires in vitro fertilization process to create the embryos which are then grown for 5-6 days in the IVF laboratory. On day 5-6 of the embryo development, a few cells are extracted from the embryos and tested for genetic disease or chromosome abnormalities. The embryos are frozen for the process of embryo transfer in a subsequent cycle. After the genetic test are done, we know which embryo is suitable for transfer.
What is the difference between PGS and PGD in the case of IVF?
Preimplantation genetic screening (PGS) is a test to check the chromosome content of the embryo in terms of correct number. Normal human has 23 pairs of chromosomes or for a total of 46 pieces. In the case of an abnormal chromosome content, the number of chromosomes will be more than 46 pieces or less than 46 pieces.