IVF technology has given a ray of hope to many couples enabling them to have their biological child. With cutting-edge techniques, advanced equipments and dedicated lab personnel, the technology ensures better clinical results. A couple taking fertility treatment, such as IVF, may be advised by their fertility doctor to have their embryos undergo genetic testing, before they are transferred into the uterus.
The two tests conducted on embryos for genetic defects are:
• Preimplantation genetic diagnosis (PGD)
• Preimplantation Genetic Screening (PGS)
After the tests, only the embryos free of genetic abnormalities are transferred into the uterus.
What is PGD?
PGD is a sort of screening done to detect genes linked to specific diseases. If either the man or the woman has a family history of a hereditary disease, this test can help ensure that the child born out of IVF will not have the condition. Either partner need not have the disease for the test to be conducted. In many cases, an individual could also be only a carrier of the gene.
Some of the diseases that PGD is employed to check for include:
• Huntington's Disease
• Exchange of chromosomal material that may cause a miscarriage, mental retardation or congenital anomaly
• Marfan Syndrome
• Cystic Fibrosis
• Duchenne Muscular Dystrophy
• An abnormal number of chromosomes
What is PGS?
PGS test determines if an accurate number of chromosomes are present in the cells of the embryo. Normal, healthy humans have a complete of 23 pairs of chromosomes. This helps to identify which embryos have a higher chance of implanting and producing a healthy pregnancy. If an embryo is having more or less than the usual number of chromosomes, then the chances of miscarriage is high. Actually, this is one of the most common reasons why a fertilized egg fails to implant in the uterus or even if it implants, the chances of miscarriages are high.
IVF has a high risk of multiple pregnancies as 2-3 embryos are transferred into the uterus to maximize the probabilities of a successful pregnancy. PGS makes it possible to transfer only a single embryo which has the highest chances of implantation and pregnancy, avoiding multiple pregnancies.
If older women are trying to get pregnant, the risk of abnormal chromosomes is higher. Thus, this test is usually for women above 35 years and going through an IVF cycle. The test is advisable if the woman has had recurrent miscarriages.
PGS isn't to test for specific diseases. As compared to PGD, this is often a simple test. However, it can help to detect Down Syndrome. It happens by the presence of an extra chromosome in the person's DNA.
What You Should Know about PGD and PGS
Both these tests use an amniotic fluid sample drawn on day three after the embryo culture. Withdrawing this sample risks the health of the fertilized egg & any damage to it will not result in a successful pregnancy. So this needs exceptionally skilled and well trained personnel. In addition, the PGS test requires samples for five to six embryos. In the case of older women, this might not be possible during a single IVF cycle. Hence, these women may require more than one IVF cycle to develop enough embryos for testing.
Therefore, it is crucial to work with a good fertility centre having expert staff.
Which Test Do You Need?
Not all couples undergoing IVF need to take both tests. The test depends on many factors such as whether or not they have had earlier unsuccessful IVF cycles, past miscarriages, medical history, a family history of genetic diseases, age of the woman etc.
If you are looking to consult a fertility specialist, call us for an appointment or visit your nearest GarbhaGudi IVF Centre. Consult with the Nation's finest Fertility & Reproductive Medicine Specialists.
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