Preimplantation genetic testing (PGT)
This can be divided into PGT for monogenic / single gene disorders & PGT for chromosome structural rearrangements (PGT-M & PGT-SR) [formerly known as preimplantation genetic diagnosis (PGD)] and PGT for aneuploidies (PGT-A) [formerly known as preimplantation genetic screening (PGS)].
PGT for monogenic / single gene disorders & PGT for chromosome structural rearrangements (PGT-M & PGT-SR)
This is an advanced technology that combines test tube baby with cell molecular genetics. This is done by removing and analysing the chromosomes (PGT-A) and genes (PGT-M / SR) of blastomeres from day 3 embryos or trophoblast cells from day 5 blastocysts. This allows the selection of embryos with normal chromosomes and without family genetic diseases to be transferred into the uterus.
PGT-M / SR is different from other prenatal diagnosis. It has an accuracy of up to 90%. Other prenatal diagnosis, which involves chorionic villus or amniocentesis tests to determine the genetic condition of the fetus, can only be done during pregnancy. The use of PGT-M / SR, which is performed before pregnancy, can avoid both psychological and physiological impact associated with abortion.
Indications for PGT-M / SR
Family history of hereditary diseases.
Couples with known chromosomal or genetic abnormalities.
PGT for aneuploidies (PGT-A)
PGT-A is a new development through combining reproductive medicine and biotechnology, from earlier fluorescent in situ hybridization (FISH) which only analyses a few specific chromosomes to later array comparative genomic hybridization (array CGH) which analyses all 23 pairs of chromosomes. PGT-A allows the detection of chromosome abnormalities in embryos.
Advantages of PGT-A
- Increases implantation rates
- Decreases miscarriage rates
Indications for PGT-A
- Recurrent miscarriage
- Repeated implantation failure
- Advanced maternal age