PGS is a genetic test done before embryo transfer (ET). For this, few cells are taken from an embryo (day 3 or day 5 i.e. Blastocyst) formed in an IVF Lab after fertilization. The removal of these cells has hardly any impact on the developing embryo, especially on Blastocyst (Day 5 embryo). These cells are removed through Laser-Assisted Biopsy by an embryologist. In a Day 5 Biopsy 4-8 Outer cells (which would form the placenta later) is taken and sent for chromosomal analysis. These cells are analyzed using the very efficient technique of Next Generation Sequencing (NGS) to determine the number of Chromosomes in a cell. Normally 46 chromosomes are there in a healthy human cell, which is known as Euploid. Sometimes, there can be an abnormal number of chromosomes e.g. 47 or 45. Such a condition is known as an Aneuploid condition e.g. Down’s Syndrome, where there are 47 chromosomes in total due to three copies of Chromosome number 21. This can be the cause of failed IVF, miscarriage or even if pregnancy occurs, the child born will have mental and physical disabilities.
To avoid such disappointment of recurrent IVF failure or miscarriage after successful IVF pregnancy, we have an option of PGS nowadays.
This test allows us to select a healthy embryo before planning embryo transfer. Though the cost of the IVF cycle may escalate 20-30% But assurity of a healthy baby along with enhanced rates of Successful IVF cycle make it quite a beneficial option.
Its specifically important for people with repeated IVF failures, recurrent miscarriages, the advanced age of mother undergoing IVF and couples having a family history of genetic diseases.
The whole process of IVF treatment remains same involving 8-10 days of injections followed by egg retrieval under anaesthesia. Fertilization in IVF lab using eggs and sperms through ICSI. When embryos develop into a blastocyst (Day 5 of fertilization), few cells are taken from the outer layer of the embryo by an expert embryologist. These cells are checked for a number of chromosomes in them. Embryos with an abnormal numbers of chromosomes, are discarded. Only the embryos with a correct number of chromosomes are used for transfer. It ensure IVF high success rate of live birth of a healthy baby.