Dr Swati Mishra, Consultant, Birla Fertility & IVF explains about Preimplantation Genetic Testing (PGT) which is a recent development in ART that is used to assess the genetic profile of the embryo before it is implanted into the mother’s uterus, thereby increasing the chances of a healthy baby
Fertility science and assisted reproductive technology (ART) have evolved significantly in today’s world. Treatment options like Intracytoplasmic Sperm Injection (ICSI), Frozen Embryo Transfer (FET), third-party reproduction is available to experience the joy of parenthood if there is a difficulty in natural conception.
PGT is a recent development in ART that is used to assess the genetic profile of the embryo before it is implanted into the mother’s uterus, thereby increasing the chances of a healthy baby. PGT helps in improving the success rate of IVF. It is a cutting-edge procedure used to identify genetic abnormalities in embryos created with In-Vitro Fertilization (IVF). The goal of PGT is to allow the physician to select embryos predicted to be free of a specific genetic condition or chromosome abnormalities for transfer. Prior to pregnancy, patients can reduce the risk of genetic diseases in their future children with the help of this test.
How does it work?
The test determines whether the embryo has any genetic defects or chromosomal errors. Prior to transfer to the uterus, these embryos are tested for chromosome and gene abnormalities. A normal number and structure of chromosomes in an embryo is called euploidy while, an abnormal number or structure is referred to as aneuploidy. PGT allows for a normal number and structure of chromosomes in an embryo (euploid) to be transferred into the uterus. After the eggs are collected in an in vitro fertilization cycle (IVF), the sperm and the eggs are fused together to form an embryo. Embryo cells are biopsied and sent for genetic testing when they reach the fifth day of development and form a blastocyst. All 23 pairs of chromosomes are tested for errors using microarray CGH (comparative genomic hybridization) or NGS technology (next-generation sequencing). Genetically normal embryos are selected for embryo transfer into women’s uteruses. Conception is more likely to be healthy, miscarriages are less likely, and conception times are reduced. The embryo transfer can be performed in the same cycle of embryo biopsy if genetic results are received within 24 hours. Following biopsy, embryos are frozen and transferred into the mother’s uterus after 1 – 2 weeks when results are reported. Genetically abnormal embryos can be discarded or used for research after consent from a couple. It is possible that the embryo biopsy and freezing will damage the embryo, but in experienced hands and with proper technique, this risk is very low or negligible.
Who needs Preimplantation Genetic Testing?
PGT cannot be offered as an extensive treatment for all couples undergoing IVF. It is recommended in couples when one or both parents have a known genetic abnormality in the family and testing is performed on an embryo to determine if it also carries the same genetic abnormality. In contrast, preimplantation genetic testing is also offered to genetically normal couples in whom embryos are tested for aneuploidy (chromosomal errors like Downs syndrome). Aneuploid embryos lead to implantation failure and miscarriage eventually resulting in unsuccessful IVF. Embryos with normal or euploid chromosomes increase the likelihood of implantation and pregnancy during IVF. It also reduces the abortion rates and time to pregnancy in IVF cycles. It also reduces the abortion rates and time to pregnancy in IVF cycles.
Preimplantation Genetic Testing:
IVF/ICSI couples are advised to undergo PGT due to the following reasons:
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To select chromosomally normal embryos from genetically healthy parents which helps to increase the success rates of IVF and reduce miscarriage rates.
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To identify genetically normal embryos from couples with single gene disorders or chromosomal problems which aids to prevent a child being born with a genetic disorder that could be fatal or could come with long term implications for the baby.
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Couples on their journey of parenthood using ART should certainly consider consulting the fertility specialists for Preimplantation Genetic Testing and discuss the benefits of undertaking such tests as well as know about the available procedures for the same.