What is Double marker?

The double marker test is a prenatal screening test that measures two blood markers to identify the risks of genetic disorders in the fetus namely trisomy 21(down syndrome), 18(Edward syndrome)and 13(Patau syndrome). It is done at 10-14weeks of pregnancy.
It is blood test.

Chromosomal anomalies can result in serious illnesses and disorders that might impair a child’s development during pregnancy or later in life. This test enables one to foresee the presence or potential occurrence of such conditions. It is one part of the Combined First Trimester Screening Test which is offered to all pregnant women(Other part being NT/NB scan).

The test measures two components in the mother’s blood: human chorionic gonadotropin(hCG) and pregnancy-associated plasma protein-A(PAPP-A). Abnormal levels of these substances may indicate an increase risk of chromosomal abnormalities of fetal developmental problems.

What Combined first trimester test screen for?

Down’s syndrome: In pregnancies with Down’s syndrome, PAPP-A levels tend to be low and hCG levels tend to be raised. When combined with results of NT/NB scan by a computer algorithm, it can detect down syndrome in around 90% cases.

It also screens for Edward and Patau syndrome.

What is first trimester Quad test?

It is also known as Enhance first trimester screening. The two new serum markers that are analyzed include placental growth factor (PlGF) and first trimester alpha fetoprotein (AFP) in addition to PAPP- A and beta hCG to generate a pregnancy specific risk for chromosomal abnormalities in the baby, risk of your baby having an open neural tube defect along with the risk of having high blood pressure during the course of pregnancy course(Pre-eclampsia) possibility of having small baby (Fetal Growth Restriction).

Why should I get this screening test?

Aneuploidy(chromosomal problem) can occur in any pregnancy although most affected embryos abort spontaneously early in the first trimester. In those who survive, Down’s syndrome (DS) is the most common form of aneuploidy. In the absence of prenatal diagnosis and therapeutic abortion, the prevalence of DS in developed countries is 1-2 per 1,000 births making it the most frequent identifiable cause of severe learning difficulty. Combined first trimester screening has the capacity to detect more than 90% of Down’s syndrome pregnancies.

What does the results mean?

It is important to keep in mind that this is a screening test and categorises babies into low risk and high risk. This will not tell whether your baby has a problem or not.

Screening is not perfect and might provide an incorrect result. It may lead to personal choices about your pregnancy.

If the result is low risk, it is unlikely for your baby to develop down syndrome.

If the result is high risk for a particular condition, It does not mean that your baby has a problem. You should consult your obstetrician/fetal medicine specialist to decide on further diagnostic testing available.

Is the test mandatory?

No. This is an optional test, but it advisable to get it done. If you have any concerns about the test, please talk to your obstetrician gynaecologist/Fetal medicine specialist.

What if I have missed the test?

You still have option of quadruple screening which is done from 15- 20weeks of pregnancy. This has sensitivity( detection rate) of around 70% for detection of Down syndrome.

There is another screening test ie NIPT/NIPS which has sensitivity of >99% for Down syndrome. This can be done anytime from 11 weeks to pregnancy.