Triple Marker Test

What is Triple Test?

Pregnancy is a nine month long journey and throughout this time, you and your baby are screened for major diseases with the help of blood tests and ultrasounds. Triple marker test is one such screening test which is done around the end of the first trimester. It is commonly called as triple test, triple screening, multiple marker or afp marker.

Triple Marker Test
Triple Marker Test

This test is mainly done to screen for genetic disorders like Down’s syndrome. It measures the presence of three substances that are secreted by the fetus and the placenta:

  • AFP Test (Alpha Fetoprotein) : AFP is a protein that is produced by the fetus. High levels of this protein are indicative of potential neural tube defects or defects in the fetus’s abdomen.
  • HCG (Human Chorionic Gonadotropin) : HCG is a hormone that is secreted by the placenta. Low levels of HCG are seen in miscarriage or ectopic pregnancy. High levels are seen in molar pregnancy or twin/multiple pregnancies.
  • Estriol : It is an estrogen that is secreted by the placenta and the fetus. Low levels may indicate the risk of the baby having Downs syndrome.

If another component called Inhibin-A is also tested, then the test is called Quadruple Test. This screen test is done for all pregnant women between 15 to 20 weeks of their pregnancy.

Indications of Triple Marker Test

This is a screening test and it gives an idea to the expectant parents about the chances of their baby having genetic diseases or chromosomal abnormality. The placenta that nourishes the baby in the womb secretes these substances which are detectable in the mother’s blood. This test is of utmost importance in the following cases:

  • Pregnant women above the age of 35 who are at a greater risk for pregnancy complications
  • Viral infection during pregnancy
  • Family history of birth defects
  • History of a similar defect in baby in the previous pregnancy
  • History of exposure to radiation in any form
  • Ladies having diabetes or on insulin treatment

How a Triple Test is Carried Out?

Triple or Quadruple test is basically a blood test and will be recommended to all pregnant ladies between the weeks 15-20 of their pregnancy. It does not require any preparation like an overnight fasting and can be done at any time of the day. It is quick and simple and is done at the doctors clinic or a laboratory.

The technician will tie a tourniquet around your upper arm which will swell up the veins below it. The most prominent vein is palpated and the area is cleaned with a disinfectant liquid. Then a needle attached to a pre-sterilized vacute bulb is inserted into the vein and the blood is collected. The tourniquet is immediately opened and the pressure is released. The needle is withdrawn and the puncture site will be compressed with a cotton swab to prevent blood from oozing out. A small cotton bandage is applied at the site. The blood is then sent to the laboratory for testing. You may feel discomfort at the puncture site for an hour or two but it will fade away soon.

Interpretation of Triple Marker Test

Interpretation Triple Marker Test
Interpretation Triple Marker Test

The results of the triple marker test are interpreted on the basis of the following factors. The final result gives a probability in the form of a ratio of the fetus having a chromosomal defect. If the probability or risk ratio is high, then further testing needs to be carried out.

  • Mother’s age
  • Ethnicity
  • Weight of the mother
  • Presence of diabetes
  • Single or multiple pregnancies
  • Number of weeks of pregnancy

If the risk ratio is low there is nothing to worry about. In case there is a high risk ratio, then further testing like amniocentesis needs to be done. Amniocentesis is testing of the amniotic fluid by drawing the fluid under ultrasound guidance.

In case the AFP levels are high, then the doctor will check by using an ultrasound for the baby’s skull and spine for neural tube defects. If the AFP levels are low with high HCG, Down’s syndrome is to be suspected. In such cases, NT scan or Nuchal Translucency scan is very important where the presence of the nasal bone is checked and the amount of fluid at the back of the baby’s neck is measured. Both these parameters combined with the results of the triple test give a fair risk ratio or probability of the presence of chromosomal abnormalities in the baby.

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