Pre Implantation Genetic Testing - A boon for couples with genetic issues.
Most patients undergoing IVF will read around the subject and from time to time we get enquries about Pre-implantation Genetic testing (PGT). PGT includes 2 procedures, viz. PGS - Preimplantation Genetic Screening and PGD - Preimplantation Genetic diagnosis. These terms are used interchangeably but they are actually different procedures. We at Cocoon Fertility recently introduced the PGD-PGS services at our Thane facility and this was inaugurated by our brand ambassador Soha Ali Khan Pataudi. This article aims to explain this advance of science.
Preimplantation genetic testing is a method of identifying a genetic defect in an embryo before it is implanted back in the womb at embryo transfer. This helps us separate embryos with a known or suspected, gene problem (PGD) or abnormal number of chromosomes (PGS) from the normal ones. Transferring back a PGT selected healthy embryo increases the chances of having a healthy baby.
To be able to do PGT a cell is removed from the embryo in a process called 'embryo biopsy'. During an embryo biopsy typically about 3-8 cells are removed from each day 5 embryo (a blastocyst), and are sent for testing for PGS or PGD as required in that particular case. The embryo is usually frozen and implanted later as the test results take a few weeks to come back. " We have recently procured the latest in IVF lasers the Hamilton Thorne - Lykos, this is a fantastic addition to our state of art IVF lab. Embryo biopsies can now be done with greater precision" said Dr Rajalaxmi Walavalkar, IVF Consultant at Cocoon Fertility.
What is PGD - preimplantation genetic diagnosis?
PGD is used when dealing with couples with a family history of a serious or deadly disease who worry about passing it on to their offspring. It is generally recommended in cases of single gene disorders, like breast cancer, sickle cell anemia, cystic fibrosis etc. Dr Anagha Karkhanis, IVF Counsultant at Cocoon Fertility added "PGD can be used to identify over 1,500 inherited single gene disorders and is 98 percent accurate identifying affected and unaffected embryos."
What is PGS or preimplantation genetic screening?
PGS checks whether the cells in an embryo contain the normal number of chromosomes, which is 46. The embryo is usually biopsied on day 5 (blastocyst stage). Embryos with a normal number of chromosomes are "euploid" and those with an abnormal number are "aneuploid." PGS allows for a embryo with normal chromosomes to be transferred into the uterus. Risk of aneuploid embryos increases with the age of the woman. An abnormal embryo is almost always likely to fail to give a healthy pregnancy. The risks of miscarriage, fetal death later in pregnancy, stillbirth or a baby with abnormalities are all raised in aneuploid embryos. PGS also helps in severe male factor infertility and in couples with previous recurrent miscarriages.
PGT cannot be offered as blanket treatment for all. Certain genetic abnormalities can manifest at a later stage of development. A genetic condition called mosaicism may exist. Mosaicism is when abnormal cells may coexist in an otherwise normal embryo and vice versa leading to test results that do not accurately reflect the chromosome status of the embryo. A critical analysis of the case is needed before PGT can be undertaken. One also needs to consider that, in theory, the embryo biopsy and freezing may cause embryo damage, though in experienced hands this risk is low.
In its' report on PGT the ASRM ( American Society of Reproductive medicine says, "No single test, however, can accurately predict the risk of all defects in a child, and many birth defects, such as those related to environmental and toxic exposures and those that are random and unexplained, are not genetically based and may not be detected with genetic screening."
Before you finally decide to go ahead with PGT there is one other factor that you must consider. PGT does not replace prenatal testing. PGT allows for diagnosis before implantation. "Prenatal testing is a part of standard routine pregnancy care and is recommended despite the fact that PGT had been done." , explained Dr Rajalaxmi Walavalkar. Prenatal testing like Nuchal Translucency scan, chorionic villus sampling or amniocentesis reconfirms the diagnosis where diagnosis remains uncertain.
Dr Anagha Karkhanis, added "It is also important to understand that PGT is not and cannot be used for sex selection or family balancing". Pre-natal sex selection is a punishable offence. PGD is indeed a boon for couples faced with risk of genetic diseases in their offspring. If you feel you are the right candidate for PGT, meet up with the expert and understand the procedure before going ahead.
Cocoon Fertility - +912271237070
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Website - http://www.cocoonfertility.com
Cocoon Fertility Branches- Thane, Versova, Dadar, Santacruz, Pune.