The Quad Screen Test for Expecting Mothers: Accuracy & Risks

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In this article:

Firstly, what is a Quad Screen Test?

When is it Done?

How is it Done and How do you Get the Results?

How Accurate is the Quad Screen?

What are the Risks?

What can I do if I Get an Abnormal Quad Screen Result?

quad screen pregnancy

Things You Should Know about Quad Screen Test for Expecting Mothers

Firstly, what is a Quad Screen Test?

A quad screen is used to assess whether your pregnancy has an increased chance of being affected with certain conditions, such as Down syndrome or neural tube defects. If your risk is low, the quad screen can offer reassurance that there is a decreased chance for Down syndrome, trisomy 18, neural tube defects, Spina bifida or any abdominal wall defects. If the quad screen indicates an increased chance of one of these conditions, you might consider additional screening or testing.

When is it Done?

In the second trimester, usually between 18 to 22 weeks of carrying the fetus.

How is it Done and How do you Get the Results?

The quad screen measures levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), estriol and inhibin A in pregnant women’s blood. Your doctor will use your age at the estimated time of delivery and the results of the quad screen to evaluate your chance of carrying a baby who has certain chromosomal conditions, neural tube defects or abdominal wall defects.

Quad screen results give the level of risk of carrying a baby who has certain conditions compared with the general population’s risk. Keep in mind that a positive quad screen simply means that levels of a few or all of the substances measured in your blood were outside the normal range. Factors that can affect the substances measured by a quad screen include:

  • A miscalculation of how long you’ve actually been pregnant
  • Carrying more than one fetus during a pregnancy
  • Presence of Diabetes or any other prolonged illness
  • Use of in vitro fertilization
  • You continued, or were exposed to, smoking during pregnancy

If your test results are positive, your doctor might recommend an ultrasound to verify the baby’s gestational age and confirm the number of babies you’re carrying.

How Accurate is the Quad Screen?

If an abnormality exists, the quad screen can detect an increased risk for approximately 85 percent of neural tube defect cases, about 80 percent of Down syndrome cases and 80 percent of Trisomy 18 cases. But the false-positive rate for the independent quad screen is very high: Only one or two out of 50 women with abnormally high AFP readings eventually prove to have an affected fetus and in the other 48 or 49, further testing reveals that there actually is no abnormality after all.

Hormone levels may be abnormal because there’s more than one fetus, the fetus is either a few weeks older or younger than originally thought or the results of the test were inaccurate or misinterpreted. Keep in mind that if NIPT is available to you, it also only involves a blood draw, and the results are much more accurate.

What are the Risks?

There are no such risks since it is a simple, routine blood-screening test. This test poses no risk of miscarriage or other pregnancy complications. As with other prenatal screening tests, however, the quad screen can cause anxiety about the possible test results and what they might mean for you and your baby.

What can I do if I Get an Abnormal Quad Screen Result?

Before you consider taking any action on the basis of prenatal screening, be sure an experienced physician or genetic counsellor has evaluated the results. If you’re carrying only one fetus and the ultrasound shows the estimated due date is correct, your doctor may offer an amniocentesis as a follow-up.

A negative quad screen doesn’t guarantee that the baby won’t have a chromosomal abnormality, single-gene disorder or certain birth defects. If your screening test is positive, your doctor will recommend additional testing to make a fully educated and thorough diagnosis.

Studies indicate that expectant women who receive abnormal results on their quad screen but receive normal results on follow-up testing such as amniocentesis may still be at very slightly increased risk of certain pregnancy complications, such as small-for-gestational-age fetus, preterm delivery or preeclampsia. If you receive results like this, ask your practitioner about whether this applies to you.

Before the screening, think about what the results mean to you. Consider whether the screening will be worth any anxiety it might cause, or whether you’ll handle your pregnancy differently depending on the results.

Sources

https://www.webmd.com/baby/quadruple-screen-quad-screen

Quad Screen Test

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