Assisted reproductive technologies have come a long way since the 1970’s… and today we have this ever-growing science providing us with newer technologies every minute!
One such miracle of science is PGS or Preimplantation Genetic Screening or Preimplantation genetic test for aneuploidy (PGT-A). Till date, we fail to comprehend the fact as to why fertility treatments do not deliver cent percent results! What happens to the embryos after they are transferred into the uterus? Why don’t all embryos give positive pregnancy tests? Apart from high risk factors in an infertile couple, this uncertain outcome of an IVF cycle is attributed to the fact that all good looking embryos need not necessarily be normal! Just like the saying goes, “It is wise not to judge a book just by its cover”! Similarly, scientific data suggests that 50 percent of all embryos formed are not genetically normal or are referred to as ‘aneuploid ’. This is where PGT-A comes into play. Besides enhancing success rates, it is best used in couples with recurrent IVF failures, recurrent miscarriages and in order to avoid multiple pregnancies. The time to conceive via an IVF cycle also diminishes as only a single chromosomally normal embryo is transferred into the uterus, hoping for a pregnancy! This is called as the elective single embryo transfer.
PGS involves taking a small biopsy of 3-4 cells from the embryo on day 3 or day 5 of its growth and examining it for any chromosomal abnormality. An embryo with more or less than 23 chromosome pairs can lead to certain genetic disorders or miscarriages. Thus, abnormal embryos are screened out and only the genetically normal embryo is transferred into the uterus
But, unfortunately, all that glitters is not gold! PGT-A too has its own limitations and does not guarantee a live birth. There are many reasons as to why this procedure is not foolproof! Some of them are:
-Maternal age plays a pivotal role in the pregnancy rates. Even with PGT-A, the live birth rates are more for a woman less than 35 years as compared to a woman of 40 years and above.
-The biopsied sample size is small as only 3-4 cells are skillfully removed to avoid any damage to the embryo. If the biopsied cells are normal, it is not imperative that the entire embryo is genetically normal.
-There is a likelihood of the embryo being “mosaic”, meaning the few biopsied cells may be abnormal and the remaining embryo normal, thus lowering the chances of embryo implantation. While healthy babies have been born all around the world after the transfer of such mosaic embryos, fertility specialists face a dilemma whether or not to transfer them.
-The embryo and the lining of the uterus (endometrium) need to be in sync in order to achieve a pregnancy!
The process of PGT-A is an expensive affair and hence many couples choose not to opt for it. Furthermore, women with advanced age have lesser number of embryos in an IVF cycle and PGT-A testing may find that none of them are fit to be transferred. This fact can be psychologically disturbing for couples, who go through a cycle without undergoing any transfers.
Hence, it is best to discuss the option of PGT-A and its success rates with your fertility specialist. Hopefully, in the coming years, we might have an answer to overcome its limitations.

Dr. Vishesha Yadav
M.S (ObGyn), Fellowship in Reproductive Medicine
Fertility Consultant at Gynaecworld.
Email: gynaecworldfertility@gmail.com
Visit : www.gynaecworld.com