Pregnancy is a time of excitement and anticipation, but it's also natural to have concerns about the baby's health. Prenatal tests are the tests that are done in pregnancy to identify any diagnosed/undiagnosed genetic condition are inherited from mother to baby. It’s an optional testing option usually done for high-risk females or for women who have a history of genetic disease in the family.
The genetic makeup: A blueprint for life
In a human body, there are millions of cells and in each cell, there are 46 chromosomes out of which 44 are autosomes and one pair is of sex chromosomes. Each parent inherits half of the chromosomes which helps us determine the inheritance of a particular disease. The Chromosomes containing the genes are studied in genetic testing.
Types of prenatal testing
Genetic testing in pregnancy can be of two types screening and diagnostic tests
Screening tests: Identify higher risk for genetic disorders. Abnormal results indicate a need for further diagnostic testing.
Methods: Analyze protein levels from the mother's blood.
Examples: Dual marker tests and quadruple marker tests.
Timing: Specific gestational ages in pregnancy.
Non-Invasive Prenatal Testing (NIPT): Uses cell-free fetal DNA from maternal blood to screen for genetic conditions.
Timing for NIPT: After 10 weeks of pregnancy.
Diagnostic tests: Confirm the presence or absence of genetic conditions.
Methods: Obtain cells from Chorionic Villi Samples (CVS) and Amniotic Fluid (AF).
Timing:
CVS: Post-10 weeks
AF: At 16 weeks
Indications for diagnostic tests:
High-risk screening test resultsMaternal age above 35 yearsHistory of stillbirthFamily history of genetic disorders
Carrier screening: Identifying potential risks
Carrier screening can be done from the blood of parents to identify changes in the genes that can be inherited from the baby and cause serious medical conditions. Haemolytic disorders like sickle cell disease and thalassemia can be identified by carrier screening. If both parents are carriers of the specific condition, the foetus could have a more serious form of the disease. Can be done anytime irrespective of gestational age and age of partners; to be done preferably before planning pregnancy if suspicion of any such disease arises in antenatal visits.
Genetic Counselling
Genetic counselling plays an important role in interpretation of various result and provide emotional support and management therapies for the family and make informed decision and be prepared for appropriate medical care.
(Author: Dr. Talat Khan, Doctor-in-charge, Medical Genetics, Metropolis Healthcare Limited)
