Quadruple (Quad) Marker Screen

 The quad marker screening may be performed to check for the chances of the following defects in the foetus:

• Down syndrome: It is also known as trisomy 21. It is a chromosomal disorder. It leads to developmental delays, lifelong intellectual disabilities and sometimes, health problems. 
• Trisomy 18: Often, this disorder is fatal by the age of 1. It is a chromosomal disorder that results in severe delay in development and structural abnormalities in the body. 
• Spina bifida: Spina bifida is a birth defect of the spinal cord and spinal bones due to the improper development or closing of the neural tube. 
• Abdominal wall defects: In these birth defects, abdominal organs such as the intestines protrude through the navel.

Quad marker screening should be performed in all pregnant women, but it is recommended in the following cases:

• Aged 35 years or older
• Have a family history of birth defects
• Had exposure to high levels of radiation
• Have diabetes and use insulin
• Use possible harmful medications or drugs during pregnancy
• Had viral infection during pregnancy

The quad marker screening is a commonly performed screening test in the second trimester of pregnancy. It is generally performed if the first-trimester screening is not available or if the prenatal care began in the second trimester. To improve the rate of detection of Down syndrome, the doctor may combine the results of the first-trimester screening along with the quad marker screening results.

You do not need to do anything to prepare for this test. You do not need to fast before this test. Your doctor may advise you to meet a genetic counsellor before the screening, or it may be part of your prenatal care appointment.

The quad marker maternal screening is a blood test. The blood sample is obtained from the vein in your arm in the following steps:

• The technician will tie a tight band, known as a tourniquet, on your upper arm. 
• He/she will wipe the site with an antiseptic.
• A needle will be inserted into the vein to draw the blood sample. You will feel a pricking sensation when the skin is pierced with the needle. 
• Once a sample is drawn, they will take off the tourniquet and remove the needle. 
• The technician will then transfer the blood sample into a labelled bottle and send it to the laboratory for testing. 

You may have a bruise on the skin where the needle was inserted; it will fade over the next few days. You may feel dizzy when the blood sample is drawn.

This screening does not have any risk of miscarriage or complications to the pregnancy. However, it may cause anxiety about what the results could mean for the baby and you.

Normal results:

If you have normal levels of inhibin A, hCG, AFP and E3, it means that your baby and your pregnancy are normal. However, no test is a confirmation that your baby will be completely healthy, and your pregnancy will not have any complications.

Abnormal results:

If your test results show that you have high levels of inhibin A and hCG and low levels of E3 and AFP, it may indicate:

• Down syndrome 
• Trisomy 18 

If you have increased levels of AFP, it could be due to a problem with the foetus. These problems include:

• Death of the foetus (usually results in a miscarriage)
• Spina bifida
• Turner syndrome (genetic defect)
• Absence of a part of the skull and the brain (anencephaly)
• Tetralogy of Fallot (heart defect)
• Defect in the baby's intestines or other nearby organs (such as duodenal atresia)

A high value of AFP could also mean that you have more than one baby in your womb.

This screening test just indicates the overall chance of having a baby with these birth defects. Increased chances (positive results) do not mean that your baby will have any of these conditions. Similarly, the decreased chances (negative results) do not guarantee that the baby will be born without any of these conditions. Along with the results of the screening test, your age at the estimated delivery time will be used to determine your chances of carrying a baby with any of these defects.

Some factors that affect the screening results include the following:

• Weight of the mother
• Race of the mother
• Miscalculation of the duration of pregnancy
• Carrying more than one baby
• Diabetes
• Smoking during pregnancy
• In-vitro fertilisation

This screening test accurately determines about 80% of the women who are carrying a child with Down syndrome. However, in about 5% of the cases, the test gives a false-positive result, which means the test result is positive, but the baby does not have Down syndrome.

If you have positive results, you may need to consider other tests as follows:

• Targeted ultrasound
• Chorionic villus sampling
• Prenatal cell-free DNA screening
• Amniocentesis

Discuss the results with your genetic counsellor or doctor to understand the results and how they affect your pregnancy.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.