When is genetic examination necessary in IVF treatment?
The wish of every parent is a healthy child. This goal is complicated when the risk of an inherited condition or chromosomal abnormality increases. Preimplantation genetic testing (PGT) for monogenic/single gene defects (PGT-M) and aneuploidies (PGT-A) provides the possibility of a solution. PGT M and PGT-A are the modern terminology, but in the past it was called preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS) or comprehensive chromosome screening (CCS).
What is genetic analysis?
PGT-M and PGT-A help to examine whether there is a problem with the embryo even before pregnancy begins. PGD begins with the in vitro fertilization process, where eggs and sperm are brought together in a laboratory environment. Five or six days after fertilization, a biopsy is done in which a small sample of cells is removed from each embryo. These cells are tested for the condition of interest and the presumed unaffected embryos are transferred to the woman’s uterus at a later time. PGT-M is the process of detecting a genetic syndrome such as cystic fibrosis, Huntington’s disease, or muscular dystrophy. PGT-A identifies chromosomal abnormalities such as Down syndrome. Post-biopsy embryos are vitrified (frozen) and stored until genetic testing is complete. PGT results are ready approximately 1-2 weeks after biopsy. In a standard IVF treatment, embryos are graded and selected for use based on their appearance or morphology. When an IVF treatment includes PGD, the selection of embryos is based on their genetic makeup. Embryos presumed unaffected can be transferred back to the uterus at any time, even in the next cycle.
In which situations is genetic analysis applied?
Couples may choose PGT testing for several reasons:
- Have undergone standard IVF treatment that failed or resulted in miscarriage
- Have had miscarriages due to an inherited chromosome rearrangement, such as a translocation or inversion
- If they have a child with a genetic condition, they may want to reduce the risk of transmission for their future children.
- If one of the parents has a genetic condition or is at high risk of developing a genetic condition, they
may want to reduce the risk of transmission for their future children.
Types of genetic diagnosis
There are a total of 46 chromosomes (23 pairs) in a human cell. Not so long ago, standard PGT-A analysis could examine only a few chromosomes. Advancing genetic technology now allows scientists to evaluate the entire set for missing and extra complete chromosomes, as well as for large missing and extra chromosome fragments (deletions and duplications).
Evaluation of the chromosome structure of an embryo using PGT methods helps to select those with the correct number of chromosomes. Transferring these embryos can result in higher implantation and pregnancy rates and may help prevent miscarriages.
There are a number of different PGT-A platforms, including CGH (comparative genomic hybridization), SNP (single nucleotide polymorphism), and NGS (next generation sequencing). Each technique ultimately performs the same task. All are highly effective with 97-99% accuracy.
Is genetic testing required before IVF treatment?
It may be required for women in their late thirties or older, women who have had previous IVF attempts or miscarriages, women who have had three or more consecutive miscarriages, and couples who may be genetically predisposed to medical problems due to their family tree.
The genetic testing process is a safe procedure that does not harm the embryo and is safe for the mother and the baby. You can get support from a specialist doctor to get personalized information about genetic testing.