Genetic Counselling FMU

Genetic Counselling

Most babies are born healthy but there is a 3-4% risk of a child being born with a birth defect or mental disability. This depends upon many factors such as maternal age, environment, family history, medical conditions of the parents, etc. prenatal screening and diagnostic tests can provide some information about some conditions. If there is a family history or repeated miscarriages, the patients are referred to genetic counseling.

The tests can fall under two categories: screening and diagnostic tests. Screening tests such as ultrasound and serum marker tests are non-invasive and provide information about the risk of a condition. Diagnostic tests are generally invasive and confirm the presence or absence of a condition. If the screening test indicated a risk of abnormal chromosome number, then this finding is confirmed by invasive tests like amniocentesis (taking out the fluid around the baby from the uterus containing floating cells of the baby) or chorionic villi sampling or CVS (taking blood from the baby’s side of the placenta). Patients are told about the range of conditions which are tested by screening tests, which are generally few. Diagnostic tests such as chromosomal microarray detect many genetic conditions.

Many patients are scared of doing invasive tests since there is a risk of harming the baby. Non-invasive prenatal testing (NIPT) uses cell free DNA from mother’s blood to detect abnormal number of chromosomes 13, 18 and 21 (Down Syndrome). But this only informs about the abnormal number. It does not detect chromosome structure defect or genetic defects in the chromosome. Nuchal translucency (NT) ultrasound scan and double and triple marker tests are done to screen in the first trimester. Upon finding any indication, a chromosomal microarray is done to confirm. In the second trimester, Target Scans are done to look for any structural abnormality in the fetus’s body and organs. If there is any family history such as an already affected child and/or parents carrying any genetic abnormality and the mother is carrying a pregnancy, then the existing child is tested to detect the disease and the fetus is tested to confirm the presence or absence of the same disease. Further counseling is provided depending on the test results. Further information about genetic counseling and fetal medicine are available on our YouTube channel.