Quadruple Test (Second-Trimester Prenatal Testing)

Quadruple Marker Test during Pregnancy

Medically Reviewed By
Dr. Prerna More Patel (Gynecologist/Obstetrician)
View more Gynecologist/Obstetrician Our Panel of Experts

Pregnancy brings many changes in life. The first visible change is to the body, but the baby’s growth is a most important change taking place invisibly inside the body. Medical tests and examinations ensure regular check to track the healthy growth of a baby but several other things need to be considered as well. Procedures like quadruple marker test are optional, but one can choose to get them done based on the risk factor that the physician suggests. Here is some relevant information on the test to help you get a clear understanding of it.

What Quad Screen Test Is & Why It is Done

Quadruple screening – also referred to as quadruple marker test, multiple marker screening, AFP plus, AFP maternal, MSAFP, and 4-marker screen – is a blood test done to assess the risk to the baby from certain health problems. The test screens chromosomal abnormalities like Down syndrome, trisomy 18, and neural tube defects such as spina bifida. Quadruple screening is done in the second trimester, that is, between 15 to 20 weeks of pregnancy, ideally after the first trimester screening test. This is called integrated or sequential screening when there are tests conducted every trimester. In case one misses the screening in the first trimester, the quadruple screening can be conducted in the second trimester too.

The screening test aims to determine genetic diseases and birth defects in the baby. Based on the results, the doctor can even suggest invasive diagnostic tests like amniocentesis (amniotic fluid test) to further assess the baby’s condition. The quadruple screening test can only highlight the risk of the baby having a birth defect, and poses no health hazard to the mother and baby. On the other hand, tests like amniocentesis can tell whether the baby has a certain birth defect, but at the same time, carry a risk of miscarriage while conducting the test.

Who Should You Go to for a Quad Screen Test?

You should consult your healthcare physician for guidance on conducting the quad screen test. Based on the risk to the mother and baby, the doctor recommends the screening. One may consult a genetic counsellor or a maternal-foetal medicine physician for more information

Many women go for screening first and then opt for invasive tests whereas others who are at higher risk of chromosomal threats directly opt for diagnostic tests which carry a certain amount of risk of miscarriage. Regardless, of what others say or have done in the past, it is the guidance and words of experienced healthcare practitioners that matters.

Pregnant woman consulting doctor for quad screen test

What Substances Are Measured in the Quadruple Marker Test?

The quad test includes the analysis of a blood sample to measure levels of four substances in the blood. Namely:

  • Alpha-fetoprotein (AFP): This is a protein made by the baby and indicates the possibility of the baby having spina bifida and anencephaly
  • Human chorionic gonadotropin (hCG): A hormone made by the placenta which is essential to maintain early pregnancy
  • Unconjugated estriol: A hormone produced by the placenta and the baby, low levels of which may indicate the possibility of Down’s syndrome or Edward’s syndrome(Trisomy 18).
  • Inhibin A: A hormone produced by the placenta which indicates the possibility of the baby having Down’s Syndrome.

When is the Quad Screen Test Done in Pregnancy?

The test is mostly conducted in the second trimester sometime between 15th to 20th week of pregnancy, but according to The American Congress of Obstetricians and Gynaecologists, women of all ages should be offered first and second-trimester screening and diagnostic tests. Although all pregnant women are recommended the test, some women should consider it seriously. These include:

  • Women who are over 35 years old
  • Women who have a family history of birth defects
  • Women whose previous child has been born with a birth defect
  • Women who have type 1 diabetes

The procedure is not complicated. The level of pain is similar to that of a normal blood test. The consulting physician can refer to a diagnostic centre or conduct the test within the hospital if facilities are available. The only complication that might arise from the blood test is bruising or fainting if you are someone who is has a phobia of blood. Make sure you identify a trustworthy lab to ensure accurate test results.

How is the Quad Screen Done?

The blood is drawn from the mother and this takes about 5 to 10 minutes. The test samples are then sent to a laboratory for further testing, and the results are ready after a few days. The quad blood test assesses the levels of four substances in the blood, namely, AFP, HCG, Estriol and Inhibin A. However the screening test does not only look for results from the blood test. Numerous factors are compared, and then the risk of the baby having an abnormality is assessed. These factors include age, ethnicity, blood test results and many more.

Preparation for quad screen test

NOTE: It should be remembered that these tests do not diagnose the problem but only indicate the potential risk that signals further testing.

How are the Results Computed?

The results of the blood test are plugged into a formula, along with the baby’s gestational age and the age of the mother. The mother’s age plays a crucial role, as the risk of having defects like Down syndrome increases with the maternal age. For example, the chances of the baby having Down syndrome are 1 to 1200 at the age of 25 years but the risk increases to about 1 to 100 at age 40.

For those who opt for a sequential or integrated quad blood test, the results will be more comprehensive, as the test results for both the trimesters will be combined.

How are Results of the Test Interpreted?

One needs to consult a medical practitioner or genetic counsellor to evaluate the medical tests and interpret the results of quadruple marker test during pregnancy. The report consists of a risk assessment ratio for Down’s syndrome, trisomy 18 and neural tube defects. For example, the result will be presented in a ratio like the following:

Chances of Down syndrome are 1 to 30 or 1 to 1000

The meaning of 1 to 30 is that one among 30 women with these results one may have a baby with Down’s syndrome. 1 to 1000 means that one among thousand women with these results will have a baby with Down’s syndrome. Thus, the higher the number, the lower the chances of risk to the child.

It should also be remembered that the test only indicates risk and not the actual defect. Higher results do not mean that the baby does not have any defect; on the other hand, a lower ratio also does not mean that the baby will be born with a defect. These are just risk indication tests.

1. What Does it Mean if the Results Are Normal?

Normal test results of quadruple marker test during pregnancy indicate that the baby is healthy and the pregnancy has fewer complications. However, there is no guarantee that these prenatal tests can provide accurate information regarding complications and the baby’s health. Around 98% of all screening tests result in a normal report. It definitely is an assurance that helps you remain stress-free during your pregnancy knowing that the baby is safe.

2. What Does it Mean if the Results Are Abnormal?

Abnormal test results are no cause for panic as they do not mean that the baby has a birth defect. The result can be abnormal, even as a result of the incorrect gestational age of the baby. In this case, the child being younger or older than expected will give abnormal results. The next step after receiving abnormal result is to have an ultrasound to check the baby’s age. Counselling and further tests may be required to identify the problem if any. There are tests that can be conducted to eliminate the risk of a positive quad screen test for Down’s syndrome. Amniocentesis is one of the tests performed and works by checking the AFP level in the amniotic fluid surrounding the baby. It is good to ask questions to the healthcare practitioner so that you can take all the right steps in order to ensure that the baby is safe. If there are even slightest chances of doubts in your mind, it is advisable to get them clarified by your doctor.

Risks Involved in a Quad Test

Apart from the discomfort of drawing blood, there are no other risks involved in the quad test. The doctor will draw a sample of the blood through the needle and send it to the laboratory for analysis. There are no risks that could harm you or the baby.

How Accurate is the Quad Screen Test?

The quadruple marker test during pregnancy only indicates the level of risk. Also, it does not pick up all cases of Down syndrome, trisomy 18 and neural defect when the baby might be actually affected. Indicating the low level of risk when the baby has a defect is called a false negative result. Whereas, an indication of high risk when the baby is not affected is called false positive report. However, consulting the physician is mandatory.

70 percent cases of trisomy 18 and 81 percent cases of Down syndrome are generally detected by the screening. This means that when tested, there is 81 percent chance of detecting and giving accurate results if the baby is suspected of having Down’s syndrome. Also, it should be kept in mind that the screening has a 5 percent false positive rate. Which means it suggests that there is a problem when no problem exists.

Based on the test results the doctor might recommend further testing to ascertain further evaluation. These may include:

  • Non-invasive ultrasounds
  • Amniocentesis
  • CVS testing – Chorionic Villus Sampling
  • Other extensive DNA testing

There are several factors that can influence the quad test results such as multiple pregnancies, effect of in vitro fertilisation, diabetes, and chemical interference. Thus, consulting a genetic counsellor is a wise move to get a clear understanding of the report and prepare for further steps.

What If the Screen Results Indicate That the Baby is at Risk?

The genetic counsellor or maternal-foetal medicine specialist can help in understanding the result and deciding on the further tests. If you decide to have an ultrasound, it will contain a detailed report on the baby’s gestational age, multiple pregnancies and the spinal cord. In case of any anomaly, the screening can be redone.

In case the baby is detected with spina bifida and the mother decides to continue the pregnancy, the medical team will monitor the baby’s condition and will be prepared to do surgery after birth. In cases of a high risk of Down’s syndrome or trisomy 18, the ultrasound will check for several markers that may give more information on the baby’s condition. If one of the markers is found, the possibility of a genetic abnormality in the baby is more.

Before considering any action based on the prenatal test, make sure that an experienced physician or genetic counsellor has evaluated the results. Anything to do with baby’s health is a point of worry but an expecting mother should keep herself free of any worry that can further affect the child’s health. Getting a clear picture of these results is important, and taking immediate steps will ensure a safe and healthy pregnancy.

Also Read: Triple Marker Test during Pregnancy

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