June 2, 2021 10:50:04 am
It is understood that while genes are the body’s blueprint — its basic physical and functional unit of heredity — not a lot of people pause to think about genetic anomalies or disorders that may be affecting their health.
Women, especially, are unaware of just how much their genes impact their health, and how prevention of certain genetic diseases can be done to ensure a healthy offspring.
Dr Hema Purandarey, consultant medical and reproductive geneticist, MedGenome Centre for Genetic Health Care shares with indianexpress.com some health conditions that women are more prone to through genetics, and the tests available to detect them.
1. Chromosomal aneuploidy in babies of expecting mothers: A condition in which a cell has an incorrect number of chromosomes. If there is an error in the normal processes of fertilization, there can be changes to the number or structures of chromosomes which can lead to an offspring with birth defects due to the abnormal structure or number.
The most commonly seen type of defect is an extra chromosome 21 called trisomy 21 or Down syndrome. Genetic screening and diagnostic tests are available with pre-test and post-test counselling which can identify these changes in the foetal state. These include specific noninvasive screening tests like NIPT and parental karyotypes and invasive diagnostic tests such as amniocentesis and chorionic villus sampling to identify the genetic makeup of the baby.
2. X-linked inherited disorders: Some disorders are X-linked, which means a female with 2X chromosomes will be a carrier, but if she passes this to her male offspring, it will be affected since males only inherit one X chromosome from their mother, the other being a Y chromosome inherited from the father. Finding out about carrier status prior to conception can help to plan genetic counselling. Testing is available for several such disorders like Fragile ‘X’, Hemophilia, Duchenne Muscular Dystrophy etc.
3. Hematological disorder screening: Couples have to be screened if they are carriers for common hematological disorders such as thalassemia and sickle cell disease. Consanguinity increases the risk of having any recessive genetic disorder by approximately 25 per cent.
A carrier screening test can help prevent both X-linked and conditions such as thalassemia and sickle cell anemia from being passed on. It also helps couples understand and plan better for their future. This is a comprehensive test screening, with the capability to detect mutations causing disease in more than 2,000 genes.
4. Recurrent pregnancy loss: Three or more consecutive pregnancy losses before 20 weeks from the last menstrual period are defined as recurrent pregnancy loss or RPL. Epidemiological studies show 1 per cent to 2 per cent of pregnant women suffer from RPL. Genetic causes of recurrent pregnancy losses account for about 2-5 per cent. Chromosomal or genetic abnormalities lead to most losses of pregnancy. The abnormality might come from the early embryo, egg, or sperm.
There are genetic tests that can help detect if the pregnancy loss was due to an abnormal number of chromosomes, and provide insights to plan and support a successful pregnancy in future.
5. Implantation failure during IVF: One in two human preimplantation-IVF embryos are chromosomally abnormal. This causes them to implant onto the uterine wall or not stay there long enough for a successful pregnancy. This leads to miscarriages and failed IVFs. If there is a family history of a genetic disorder, the fertilized embryo can be tested using pre-implantation genetic testing. If a donor was used, the donor sperm or the egg can be tested.
6. Hereditary breast and ovarian cancer: In women, approximately 15 per cent of all ovarian cancers and 7 per cent of all breast cancers are caused by mutations in the BRCA1 and BRCA2 genes. At present, we have predictive tests like BRCA1 and BRCA2 gene tests for this. Actor Angelina Jolie had a history of breast and ovarian cancer. So, she asked to be genetically tested and when it was clear she was susceptible, she had the required surgeries. Early detection can not only save life but also reduce the financial burden of advanced treatment.
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