Preimplantation Genetic Testing (PGT) is a technique used in conjunction with in vitro fertilization (IVF) to screen embryos for genetic abnormalities before transferring them to the uterus. This process helps ensure that only healthy embryos are implanted, increasing the chances of a successful pregnancy and reducing the risk of genetic disorders.
Types of PGT
- PGT-A (Preimplantation Genetic Testing for Aneuploidies): Screens embryos for chromosomal abnormalities, such as extra or missing chromosomes (aneuploidies). Common aneuploidies include Down syndrome (trisomy 21), Turner syndrome (monosomy X), and Klinefelter syndrome (XXY).
- PGT-M (Preimplantation Genetic Testing for Monogenic Disorders): Tests for specific single-gene disorders that one or both parents may carry, such as cystic fibrosis, Tay-Sachs disease, or Huntington’s disease.
- PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements): Detects structural chromosome rearrangements, such as translocations or inversions, which can lead to implantation failure, miscarriage, or genetic disorders.
The PGT Process
- Ovarian Stimulation and Egg Retrieval: The woman undergoes ovarian stimulation with hormonal medications to produce multiple eggs, which are then retrieved through a minor surgical procedure.
- Fertilization: The retrieved eggs are fertilized with sperm in the laboratory to create embryos.
- Embryo Biopsy: On the third or fifth day of embryo development, a few cells are carefully removed from each embryo. This biopsy does not harm the embryo’s ability to develop normally.
- Genetic Analysis: The biopsied cells undergo genetic testing to identify any abnormalities. This process can take several days.
- Embryo Selection and Transfer: Only embryos that are free of genetic abnormalities are selected for transfer to the uterus. This increases the likelihood of a healthy pregnancy and reduces the risk of miscarriage or genetic disorders.
Benefits and Considerations
Benefits: PGT can significantly increase the success rates of IVF by ensuring only healthy embryos are transferred. It can also prevent the transmission of genetic disorders to offspring.
Considerations: The procedure is complex and expensive, and not all embryos may be suitable for testing. There are also ethical considerations regarding the selection of embryos.
PGT represents a powerful tool in reproductive medicine, offering hope for couples at risk of genetic disorders and improving overall IVF outcomes.