The test measures levels of four pregnancy hormones:
Alpha-fetoprotein (AFP) -- a protein produced by the baby
Human chorionic gonadotropin (hCG) -- a hormone produced in the placenta
Unconjugated estriol (uE3) -- a form of the hormone estrogen produced in the fetus and the placenta
Inhibin A -- a hormone released by the placenta
If the test does not measure levels of inhibin A, it is called the triple screen test.
To determine the chance of your baby having a birth defect, the test also factors in:
Your ethnic background
Your baby's gestational age (measured in weeks from the day of your last period to the current date)
How to Prepare for the Test
No special steps are needed to prepare for the test.
How the Test will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
The test is done to find out if your baby might be at risk for certain birth defects, such as Down syndrome and birth defects of the spinal column and brain (called neural tube defects). This test is a screening test, so it does diagnose problems.
Certain women are at greater risk for having a baby with these defects, including:
Women who are over 35 years old during pregnancy
Women taking insulin to treat diabetes
Women with a family history of birth defects
Normal levels of AFP, hCG, uE3, and inhibin A.
Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
An abnormal test result does NOT mean that your baby definitely has a birth defect. Often, the results can be abnormal if your baby is older or younger than your doctor or nurse had thought.
If you have an abnormal result, you will have another ultrasound to check the age of the developing baby.
More tests and counseling may be recommended if the ultrasound shows a problem. However, some people choose not to have any more tests done, for personal or religious reasons. Possible next steps include:
Amniocentesis, which checks the AFP level in the amniotic fluid surrounding the baby
Tests to detect or rule out certain birth defects (such as Down syndrome)
Ultrasound to check the baby's brain, spinal cord, kidneys, and heart
During pregnancy, increased levels of AFP may be due to a problem with the developing baby, including:
Absence of part of the brain and skull (anencephaly)
Defect in the baby's intestines or other nearby organs (such as duodenal atresia )
Death of the baby inside the womb (usually results in a miscarriage)
The quadruple screen can have false-negative and false-positive results (although it is slightly more accurate than the triple screen). More tests are needed to confirm an abnormal result.
If the test is abnormal, you may want to talk to a genetic counselor.
Simpson JL, Richards DS, Otano L, et al. Prenatal genetic diagnosis In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies. 6th ed. Philadelphia, PA: Saunders Elsevier; 2012:chap 11.
Williams DE, Pridjian G. Obstetrics. In: Rakel RE, ed. Textbook of Family Medicine. 8th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 21.
ACOG Committee on Practice Bulletins. ACOG practice bulletin no. 77: screening for fetal chromosomal abnormalities. Obstet Gynecol. 2007;109:217-227.
Anderson CL, Brown CE. Fetal chromosomal abnormalities: Antenatal screening and diagnosis. Am Fam Physician. 2009;79:117-123.
Driscoll DA, Morgan MA, Schulkin J. Screening for Down syndrome: changing practice of obstetricians. Am J Obstet Gynecol. 2009;200:459.e1-459.e9.
Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, WA; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.