What is Double/Triple Marker Test
With the advancement of Science, now it is possible to detect genetic disorders in foetus itself. Marker tests are done to analyse the chances of an unborn suffering from genetic disorders mainly Down’s Syndrome.
Double marker test
Double marker test is done between 10-13 weeks of pregnancy. It assesses the risk of Down’s syndrome, trisomy 18 trisomy 21 in the foetus.
Double marker test is a blood test where Free Beta HCG (human chorionic gonadotropin) and PAPP-A(Pregnancy Associated Plasma Protein) markers are checked in the blood. This test also checks ultrasound nuchal scan to check for chromosomal abnormalities. Nuchal translucency (NT) is the translucent area at the back of the baby’s neck.This translucency is caused by the fluid and thickness of this area determines whether to go for further analysis or not. This area diminishes after 14 weeks so it should be checked before the completion of 14 weeks.
Triple marker test
It is done between 14 to 20 weeks of pregnancy. Along with ultrasound scan, the triple marker screen test analyzes how likely an unborn baby is to have genetic disorders like Down syndrome, Edwards syndrome, neural tube defects. It also detects multiple infants and an improper timeline.
Triple marker test measures the levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), and estriol in placenta. There is the option of quadruple marker test which also analysis the level of inhibin A along with aforementioned 3 substances. These tests are also known as multiple marker tests.
Risks and Options
The chances of having a baby with Down Syndrome become higher after the age of 35. About one in 20 women above the age of 35 years is at risk of having a baby with Down’s Syndrome. Results are interpreted as “Screen Positive” which indicates high risk and “Screen Negative” shows low risk for Down’s syndrome and other genetic orders. If the scan reveals a high probability of Down’s Syndrome, amniocentesis is to be done for confirmation. The results are interpreted not only based on values of these markers but also on the basis of mother’s age and fetal age.
If the tests come as positive and there is high risk of genetic disorders in baby then parents have the option of getting the pregnancy terminated. In India the pregnancy can be terminated till 20 weeks.
Who needs these tests?
Women above the age of 35 years must undergo these tests. Sometimes doctors may advise even younger women to undergo the tests if need arises.
The results may not be 100% correct and sometimes false positives and false negatives can also be seen. Double/triple marker tests cost at least INR 25000 and the costs may go up as well.