Advancements in medical technology have transformed prenatal care, allowing expecting mothers to learn more about the health and well-being of their developing babies. One such crucial test is the quadruple marker test, which assesses the risk of certain genetic conditions and birth abnormalities.
This comprehensive guide will delve into the quadruple marker test, why it’s performed, how to do it, and what the findings mean.
What is the Quadruple Marker Test?
Quadruple marker test, also known as the Quad screen or Quad test, is a blood test conducted during the second trimester of pregnancy, typically between the 15th and 20th week. This non-invasive test evaluates the risk of chromosomal abnormalities or neural defects in the developing baby during pregnancy. It derives its name from the four substances it measures in the mother’s blood:
- Alpha-fetoprotein (AFP) – a protein produced by the developing baby’s liver
- Human chorionic gonadotropin (HCG) – a hormone secreted by the placenta
- Estriol – a hormone produced by both the placenta and the baby’s liver
- Inhibin A – another hormone secreted by the placenta and ovaries
It is essential to understand that the quad test is a prenatal screening tool rather than a definitive diagnostic method for detecting chromosomal abnormalities or neural tube defects. If the results indicate abnormalities, your healthcare provider will recommend further diagnostic tests to confirm the findings.
Who Should Undergo the Quad Test?
The quad test is not mandatory for all pregnant women. Your healthcare provider might suggest the test as a screening measure if you have high-risk factors for chromosomal abnormalities or neural tube defects, which could include:
- Maternal age exceeding 35 years
- Family history of chromosomal anomalies
- History of radiation exposure
- A history of chromosomal abnormalities or neural tube defects in a prior child
- Chronic smoking history
- Maternal diabetes
- Maternal obesity
- Inadequate maternal folate levels
- Presence of a seizure disorder in the mother
- Viral infections during pregnancy
- Maternal use of specific drugs like valproate, carbamazepine, etc.
- Inconclusive outcomes from double marker tests or first-trimester scans
What Purposes Does the Quadruple Marker Test Serve?
The quadruple marker test serves as a second-trimester screening tool for the evaluation of the following conditions:
Down syndrome (trisomy 21) – a genetic disorder characterized by an extra copy of chromosome 21
Edward’s syndrome (trisomy 18) – a genetic disorder characterized by an extra copy of chromosome 18
Neural tube defects (NTDs) – occur when the neural tube, the initial structure forming the baby’s brain and spinal cord, doesn’t close properly during embryonic development. NTDs include:
Anencephaly (absence of a significant portion of the skull and brain)
Spina bifida (defect in the spine or spinal cord)
Encephalocele (Protrusion of the brain through the skull bone)
Abdominal wall defects – congenital issues where a baby’s abdominal wall has an opening, allowing organs like the intestine, liver, or stomach to protrude outside. It involves:
Omphalocele: A midline defect covered by a sac that contains protruding contents.
Gastroschisis: An abdominal wall defect usually on the right side of the umbilicus where herniated contents are not covered by a sac.
What Is the Procedure for Quad Screen?
The procedure includes the following steps:
- First, a tourniquet (a device used to apply pressure to stop the blood flow) is tied around your arm.
- Then, an alcohol-soaked cotton swab is used to clean the injection site.
- A small needle will be inserted to collect the blood from your arm into a test tube.
- After removing the needle, an adhesive sticker is placed on the puncture site.
- The sample is sent to a laboratory for processing and testing.
What Does the Result Mean?
The Quad test results are generally shown as a probability or risk score. It’s essential to remember that higher risk does not definitively mean that the baby has a genetic condition but rather an increased likelihood. Many expectant mothers with high-risk results still have healthy babies.
Your healthcare provider will suggest further diagnostic tests in case of abnormal test results. These diagnostic examinations can include:
- USG in pregnancy (an imaging test to detect potential birth defects or abnormalities in the developing baby)
- Amniocentesis (a prenatal diagnostic procedure involving the withdrawal of a small amount of amniotic fluid from the uterus to analyze fetal genetic and chromosomal problems)
Consult a healthcare provider if you want to learn more about the Quad test or have concerns.