Maternal Marker Test
Jun 04, 2020
What is a maternal marker?
A marker, simply put, is an indication. Certain substances in the body become indicators for a specific medical condition, depending on their quantities as tested against the permissible or normal range. Similarly, substances present in a pregnant woman’s blood serum are used as markers during prenatal screening for certain foetal abnormalities, such as genetically transmitted diseases and birth defects.
What are the common maternal serum markers?
Alpha-fetoprotein (AFP), estriol, human chorionic gonadotropin (hCG), and inhibin-A are some common substances that serve as markers for foetal abnormalities. Apart from these blood analytes, bio-physical properties of the mother or the foetus also serve as prenatal markers.
These markers are not used for the diagnosis of a disorder, but simply to indicate a possible risk and to check if further testing is necessary. They may be used singly, or in combination with other markers. A cut-off level is determined to check whether the result is positive or negative, but this is arbitrary and often takes into consideration factors like the false-positive rate.
How does this work?
Specific markers, or specific combinations of markers, are associated with certain conditions. Some of them are foetal neural tube defects, chromosomal abnormalities, cardiac defects, and more recently, pregnancy complications like pre-eclampsia. All markers are analysed through blood tests.
Double marker- PAPPA , HCG is done in the first trimester. This test determines if there are any abnormalities in the development of chromosomes of the fetus. The test helps detect neurological disorders like Down’s Syndrome and Edward’s Syndrome. Chromosomal abnormalities can result into serious developmental deformities and may cause varioushealth problems after birth in the child. But the risk of getting such defects is very low. Chance of getting this kind of chromosomal disorders and probability of suffering conditions like Down’s syndrome (Trisomy 21), or Edward’s syndrome (Trisomy 18) is very rare
In the second trimester- Triple Marker – AFP , HCG, Estriol , Quadruple Marker - AFP , HCG, Estriol , inhibin a, - Gynecologist may prescribe either of them. These tests usually helps to find fetal anomalies.
AFP is synthesised by the foetus in substantial quantities during the early stages of development. AFP levels in maternal blood serum are much lower. In fact, a high level of AFP in the mother’s serum is a marker of open neural tube defects which may cause spina bifida and anencephaly. Spina bifida affects the backbone and the spinal cord and may even result in partial paralysis along with loss of bowel and bladder control. Babies with anencephaly have underdeveloped brains and skulls and are usually stillborn or do not survive for long after birth.
High AFP levels may also be generated by twin foetuses, in which case there is no abnormality.
Low levels of AFP and estriol and high hCG levels are associated with a risk of Down syndrome (trisomy 21). Low levels of all these three markers suggest Edward Syndrome (trisomy 18).
Further diagnostic tests include the following:
Blood and Urine Tests: Complete Blood Count, Complete Urine Examination, Urine culture and sensitivity , Thyroid , HIV , Hepatitis , Syphilis, Diabetes test, Blood Pressure test.
A test of the amniotic fluid surrounding the foetus, known as amniocentesis, is done to diagnose chromosomal abnormalities and open neural tube disorders, between the 15th and 20th weeks of pregnancy. Another test called chorionic villus sampling (CVS) takes a sample of the placenta to test it for evidence of chromosomal abnormalities. This test does not reveal neural tube disorders and needs to be followed up by a blood screening between 16 and 18 weeks of pregnancy. Unlike these two diagnostic tests, maternal marking tests are only preliminary tests that do not give conclusive results.
Why is it important to get a maternal marker test done?
Prenatal screening allows for early detection of potential life-threatening genetic illnesses and tells the doctor if further probing is required. And it is a good starting point for monitoring the foetus and clear any doubts surrounding its health.
At Apollo Diagnostics, we acknowledge the sensitivity of the issue as well as its significance and implications (or the lack thereof). Our maternal marker testing procedures are authentic and transparent. Find your nearest Apollo Diagnostics centre here.
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