How Preimplantation genetic testing (PGT) Identifies Embryos with Chromosomal Abnormalities: explains Doctor

Mumbai: Preimplantation genetic testing (PGT) is a form of prenatal genetic diagnosis to check for abnormal embryos, thereby transferring those embryos that are genetically normal. This technology is an integral part of Assisted Reproductive Technology (ART) procedures as it helps in testing an embryo for chromosomal abnormalities. Many embryos detected with chromosomal abnormalities will not lead to a pregnancy or cause miscarriage. This test will help women to rule out any genetic disorders in their babies.

All women have the risk of having eggs that are chromosomally abnormal, and all men run the risk of some chromosomal abnormalities in sperms. The percentages of embryos that are abnormal depend on factors like age and the health history of the parents. Preimplantation genetic testing (PGT) helps to detect genetic defects in embryos created via in vitro fertilization (IVF) before pregnancy. “PGT will allow one to know about problems like cystic fibrosis, Huntington’s disease, muscular dystrophy, BRCA1 & BRCA2 mutations, Fragile-X syndrome, Tay-Sachs disease, a missing or an extra chromosome in the embryo causing the Down syndrome, sickle cell anemia), or the rearrangement of genes, lead to pregnancy loss and birth defects,” said Dr. Priya Deshpande, Consultant Maternal Foetal Medicine, Motherhood Hospital, Kharghar

Sometimes the couple undergoing fertility treatment have a structural rearrangement of their chromosomes. Some of these chromosomal rearrangements can lead to abnormality in resulting embryos. In other couples, either one or both of the parents may be carriers of a gene mutation that can result in a known genetic disorder. The resultant embryos of such a couple can inherit the genetic disease.

Dr Richa Jagtap, Clinical Director & Consultant Reproductive Medicine at NOVA IVF Fertility, Mumbai added, “PGT is a genetic test of embryos carried out in a lab after ICSI is used to form embryos. Before the embryos (blastocysts) are returned to the uterus, they are tested through (preimplantation genetic testing). This test will help embryos without translocations to be chosen to increase the chance of a healthy pregnancy. Cells from the embryo can also be tested for a pre-diagnosed gene that may produce a specific disease. This will show if an embryo is normal (means has no disease) or affected (has any problem). It will also help to understand whether the embryo is carrying the disease but unaffected by it. An unaffected carrier can be one who can pass the disease to the baby, but does not have any signs of the disease. Embryos with flaws are not transferred to the mother’s womb for a pregnancy.”

“Preimplantation genetic testing (PGT) is a screening test for someone who has a genetic disorder or is a carrier of it. It can also be advised to one with recurrent miscarriage, or for a couple who have had children with genetic disorders of single gene mutation or abnormal number of chromosomes. Preimplantation genetic testing (PGT) allows for detecting genetic abnormalities in embryos that are created via in vitro fertilization (IVF- ICSI), and only embryos without a specific genetic condition or without chromosome abnormalities are used for transfer. This testing will lower the chances of genetic disease in the baby. Before taking this test, genetic counseling is recommended for parents to understand it. If you are supposed to go for PGT, you will need to undergo an IVF cycle to retrieve eggs and create embryos. The embryos are monitored in the laboratory after fertilization till they develop into blastocysts, and a few of the cells present on the outside of the embryo ( trophoectoderm) are biopsied and sent for genetic analysis to confirm any abnormalities. The embryos biopsied are frozen and stored in the lab till the reports for embryos is received and the one healthy embryo can be chosen to be replaced in the womb of a woman at an opportune time concluded Dr. Richa, NOVA IVF Fertility, Mumbai



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