Pre-implantation Genetic Testing (PGT) refers to genetic profiling of embryos prior to implantation. It is a technique where cells are removed from the embryos and are genetically analysed for genetic defects. After analysis only the healthy embryo will be transferred to the patient. PGT thus is an adjunct to assisted reproductive technology, and requires IVF/ICSI to obtain embryos for evaluation.
Patients who will benefit from this treatment
Patients who have a child with a genetic disease
Patients who are known carriers of a genetic disease
Patients who’ve experienced recurrent miscarriages
Patients who’ve experienced multiple failed IVF cycles
Patients with advanced maternal age
PGT can be divided in to 3 categories.
Pre-implantation genetic testing for aneuploidy (PGT-A)
The goal of PGT-A (PGD/PGF) is to identify embryos with de novo aneuploidy, the presence of either too many or too few chromosomes, in chromosomally normal parents. Theoretically, avoiding transfer of these embryos will reduce the risk of miscarriage and complications related to pregnancy failure and improve the probability of conceiving a viable pregnancy.
This is beneficial in identifying,
- Down’s syndrome (trisomy 21)
- Edward’s syndrome (trisomy 18)
- Patau’s syndrome (trisomy 13)
- Turner’s syndrome (monosomy X)
Pre-implantation genetic testing for monogenic (single-gene) disorders (PGT-M)
The goal of PGT-M is to establish a pregnancy that is unaffected by specific genetic disorder inherited through a known heritable genetic mutation carried by one or both biological parents. PGT-M makes it highly likely that the baby will be free of the disease under consideration.
This is important for patients, who are carriers of disorders such as,
- Thalassemia
- Polycystic kidney disease
- Neurofibromatosis
- Haemophilia
- Hydrocephalus
- Fragile X syndrome
Pre-implantation genetic testing for structural rearrangements (PGT-SR)
The goal of PGT-SR is to establish a pregnancy that is unaffected by a structural chromosomal abnormality (translocation) in a couple with a balanced translocation, or Inversions.