In simple words, a marker is an indication. The presence of certain substances in the body becomes an indicator of certain conditions. 

Likewise, substances present in a pregnant woman’s blood serum can be used as markers during prenatal screening for certain fetal abnormalities like genetic diseases and birth defects.

The common maternal serum markers

Early in their pregnancy, all women are offered a screening of several blood markers. These can indicate increased fetal risk for certain genetic diseases and birth defects. 

Double marker test

It is a maternal serum screening test that is performed during the first trimester, between 9 weeks and 12 weeks of pregnancy, and the ideal time is 11 weeks to 13 weeks. 

It is classified as a predictive test, wherein the results report the likelihood of chromosomal abnormalities.

This test screens specifically for blood levels of both free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A).

The blood levels alone don’t produce results. The blood test is used along with ultrasound details like crown-rump length (CRL), nuchal translucency value (NT), and nasal bone status. 

Double marker test screening was previously recommended if you were over the age of 30 or have an elevated risk of chromosomal issues, such as if you have a family history of certain conditions. But today, a double marker test is mandatorily performed during the first trimester of pregnancy. 

The double marker test is a simple blood test and you can expect to receive your results within about 3 days to a week.

Triple Market Test

Also known as the triple test, multiple marker test, multiple marker screening, and AFP Plus, a triple marker test analyses how likely an unborn baby is to have certain genetic disorders. It measures the levels of three important substances in the blood:

• Alpha-fetoprotein (AFP)
• Human Chorionic Gonadotropin (HCG)
• Unconjugated Estriol (UE3) 

Triple marker screening is considered as a blood test that is performed during the second trimester. It is done in women who are between 15 weeks and 20 weeks and 6 days pregnant. The ideal time for performing this test is 16 to 18 weeks of pregnancy. 

An alternative to this test is the quadruple marker screen test, which also looks at a substance called inhibin A.

This test helps prospective parents prepare and assess options. They also alert doctors to watch a fetus more closely for other signs of complications.

The test is often most recommended for women who:

• are 30 years old or older
• have a family history of birth defects
• have diabetes and use insulin
• have been exposed to high levels of radiation
• had a viral infection during pregnancy

Quadruple Marker Screen

The quad screen, or quad marker screening, is a blood test done during the second trimester, that gives expectant moms and their healthcare providers useful information about potential developmental problems within the baby’s brain, spinal cord, and neural tissues.

“Quad” refers to the fact that the screening tests four factors in your blood. It can help your healthcare provider determine if your fetus has the marker or sign for Down syndrome and other genetic disorders.

Your healthcare provider may recommend having a quad screen if you:

• are 30 years or older
• had a viral infection during your pregnancy
• have a family history of congenital disabilities (birth defects)
• have been exposed to high levels of radiation
• have diabetes and use insulin
• used harmful medications or drugs while pregnant

A quad screen checks for four things in your blood:

• Alpha-fetoprotein (AFP) 
• Unconjugated estriol (UE) 
• Human chorionic gonadotropin (hCG) 
• Inhibin-A 

Significance of pregnancy markers

Prenatal screening is now an established part of routine antenatal care, with specific markers, or specific combinations of markers, being associated with certain conditions. 

The common disorders being screened for include:

• Chromosomal abnormalities such as (trisomy 21) Down Syndrome, (trisomy 18) Edwards Syndrome, and (trisomy 13) Patau Syndrome
• Fetal neural tube defects (NTDs) such as anencephaly and spina bifida,
• Structural abnormalities

Apart from these blood analytes, the bio-physical properties of the mother or the fetus also serve as prenatal markers.

These markers are useful in indicating a possible risk and to paves the way to check if further testing is necessary. A marker may be used singly or in combination with other markers. A cut-off level determines whether the result is positive or negative.

These are only screening tests. The confirmatory tests include NIPT or Chromosome Analysis in Amniotic Fluid. 

To Conclude

Prenatal screening allows for early detection of potentially life-threatening genetic illnesses. It tells the doctor if further probing is required and is a good starting point for monitoring the fetus and clearing any doubts surrounding its health.