According to the WHO report, the estimated prevalence of Down syndrome is approximately 1 in 1,000 to 1 in 1,100 live births globally. Annually, an estimated 3,000 to 5,000 infants are born with this genetic abnormality.
What is (PGT-A)?
Preimplantation Genetic Testing for Aneuploidy (PGT-A), previously referred to as preimplantation genetic screening (PGS), is a method employed in the context of in vitro fertilisation (IVF) to assess embryos for chromosomal irregularities prior to their integration into the uterine cavity. Aneuploidy is a condition characterised by an atypical chromosomal count, encompassing the presence of an additional or absent chromosome. The primary objective of PGT-A is to detect embryos that possess atypical chromosomal numbers.
People or couples who are going through IVF and may be more likely to have embryos with chromosomal problems are often told to take PGT-A. This is because of things like the mother’s advanced age or a history of multiple losses. By choosing chromosomally normal embryos for transfer, PGT-A can raise the success rates of IVF and lower the risk of having a child with Down syndrome (Trisomy 21) or other chromosomal diseases.
Here’s how Down syndrome can be detected through PGT-A with IVF:
IVF Process:
It is common for PGT-A to be done as part of IVF. As babies are being made, eggs are taken from a woman’s ovaries and fertilised with sperm in a lab.
Embryo Culture:
The embryos undergo a period of development within a controlled laboratory setting for several days. In general, this procedure facilitates the development of embryos to a developmental stage characterised by the presence of many cells.
Embryo Biopsy:
On the fifth or sixth day of embryonic development, a limited number of cells are extracted from each individual embryo. The biopsy procedure typically involves the extraction of a limited number of cells from the trophectoderm, which is the outermost layer of the embryo. The biopsy procedure is characterised by its low invasiveness and minimal impact on the embryo.
Genetic Analysis:
The cellular samples acquired from the embryo biopsy are thereafter subjected to analysis for chromosomal abnormalities through the utilisation of diverse genetic testing methodologies. PGT-A analysis primarily aims to identify aneuploidies, which are abnormalities in the chromosomal count. In relation to Down syndrome, the genetic study focuses on identifying the existence of an additional copy of chromosome 21.
Selection of Normal Embryos :
The selection of embryos for transfer into the uterus is based on the findings of the genetic study, which includes embryos with the accurate number of chromosomes, including those without an additional copy of chromosome 21.
Embryo Transfer:
The chosen embryos are implanted into the woman’s uterus with the objective of achieving pregnancy. Untransferred embryos can be cryopreserved for future utilisation.
CONCLUSION:
By utilising preimplantation genetic testing for abnormalities (PGT-A) in conjunction with In vitro fertilisation (IVF), individuals or couples undergoing reproductive therapy can enhance the probability of selecting embryos that exhibit chromosomal normalcy, therefore mitigating the likelihood of conceiving a child with Down syndrome or other chromosomal abnormalities.
However, it’s important to note that while PGT-A can increase the likelihood of selecting normal embryos, it does not guarantee a successful pregnancy or completely eliminate the risk of chromosomal abnormalities.