Preimplantation genetic screening or PGS (also often known as aneuploidy screening) is a procedure in which the embryos created through intracytoplasmic sperm injection (ICSI) are examined for chromosomal abnormalities. Pregnancies where embryos show chromosomal abnormalities often end in miscarriages or could result in conditions such as Down Syndrome.
This is a genetic test where the cells are examined to pick up any abnormal chromosomes (Abnormal chromosomes happen when the cells of eggs, sperm, and embryos divide leading up to too many or too few chromosomes, or with missing or added pieces of chromosomes) in the embryo.
Preimplantation Genetic Screening is done for those who have had recurrent implantation failure. This means that the patient had undergone several IVF cycles which have failed, in spite of having good quality embryos. Women who have had recurrent miscarriages are also suggested with Preimplantation Genetic Screening.
PGS can also be recommended in cases when the women opting for pregnancies are over the age of 40. A fertility specialist may also recommend it if there has been a history of some chromosomal abnormalities.
Here are some indications for PGS
- Women with recurrent pregnancy loss (miscarriages)
- Women with recurrent IVF failures
- Women with advanced maternal age
- To identify any chromosomal abnormalities which could be contributing to the problem.
The process involves growing the embryos in the lab for up to 5 days after the eggs retrieved following stimulation of ovaries are fertilised with ICSI procedure. After that, a biopsy of a few cells in the trophectoderm layer (outer layer of an embryo) is taken and sent for genetic examination. The cells are checked for any chromosomal abnormalities in the embryo, due to which the miscarriages are happening. The process also identifies the normal embryos, so these will be replaced in the women to achieve a healthy pregnancy.
As it can take up to a week for the results of the PGS tests to be available, usually all the biopsied embryos are frozen. Once the results are available, embryos that are chromosomally normal are implanted in a frozen embryo transfer process and the chromosomally abnormal embryos are destroyed.
PGS is a developing procedure and with new technology coming into the field diagnosing abnormalities is better, however, it’s not entirely risk-free. Research has shown that often the cells in an embryo are not chromosomally identical (called mosaicism) and PGS bases its findings on a small set of cells.
Despite a limited risk to the embryo that is being tested, it is a procedure to opt for in certain cases such as when the age of the women are over 40, there is a history of some sort of genetic abnormality and where there have been a few failed IVFs and miscarriages.
We have been offering this advanced technology for indicated couples since 2013.
The expertise of the clinical and embryology team matters most here are we are in a privileged position to offer this technology.
Watch Dr Vyjayanthi explain about the process of Preimplantation Genetic Screening