The quad screen — also known as the quadruple marker test, the second trimester screen or simply the quad test — is a prenatal test that measures levels of four substances in a pregnant woman's blood:
- Alpha-fetoprotein (AFP), a protein made by the developing baby
- Human chorionic gonadotropin (HCG), a hormone made by the placenta
- Estriol, a hormone made by the placenta and the baby's liver
- Inhibin A, another hormone made by the placenta
Ideally, the quad screen is done between weeks 15 and 18 of pregnancy — the second trimester. However, the procedure can be done up to week 20.
The quad screen is used to evaluate whether your pregnancy has an increased chance of being affected with certain chromosomal conditions, such as Down syndrome. The alpha-fetoprotein part of the test can help evaluate the chance for neural tube defects, such as spina bifida, and abdominal wall defects, such as omphalocele.
If your risk level is low, the quad screen can offer reassurance that there is a decreased chance for Down syndrome, trisomy 18, neural tube defects and abdominal wall defects. If the quad screen indicates an increased chance of one of these conditions, you might consider additional screening or testing.
Oct. 21, 2015
- Messerlian GM, et al. Down syndrome: Overview of prenatal screening. http://www.uptodate.com/home. Accessed Aug. 6, 2015.
- Messerlian GM, et al. Laboratory issues related to maternal serum screening for Down syndrome. http://www.uptodate.com/home. Accessed Aug. 6, 2015.
- Messerlian GM, et al. First trimester combined test and integrated tests for screening for Down syndrome and trisomy 18. http://www.uptodate.com/home. Accessed Aug. 6, 2015.
- NINDS anencephaly information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/anencephaly/anencephaly.htm. Accessed Aug. 6, 2015.
- NINDS spina bifida information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/spina_bifida/spina_bifida.htm. Accessed Aug. 6, 2015.
- Ostermaier KK. Down syndrome management. http://www.uptodate.com/home. Accessed Aug. 6, 2015.
- Frequently asked questions. Pregnancy. Screening tests for birth defects FAQ165. American College of Obstetricians and Gynecologists. http://www.acog.org/Patients/FAQs/Screening-Tests-for-Birth-Defects. Accessed Aug. 6, 2015.
- Bianchi DW, et al. Genome-wide fetal aneuploidy detection by maternal plasma DNA sequencing. Obstetrics & Gynecology. 2012;119:890.
- Cunningham FG, et al. Prenatal diagnosis. In: Williams Obstetrics. 24th ed. New York, N.Y.: The McGraw-Hill Companies; 2014. http://www.accessmedicine.com. Accessed Aug. 3, 2015.
- Fischbach FT, et al. Prenatal diagnosis and tests of fetal well-being. In: A Manual of Laboratory and Diagnostic Tests. 9th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2014.
- Beckmann CRB, et al. Genetics and genetic disorders in obstetrics and gynecology. In: Obstetrics and Gynecology. 7th ed. Baltimore, Md.: Lippincott Williams & Wilkins; 2014.
- Hochberg L, et al. Prenatal screening and diagnosis of neural tube defects. http://www.uptodate.com/home. Accessed Aug. 6, 2015.
- Wolfberg A, et al. Noninvasive prenatal testing using cell-free nucleic acids in maternal blood. http://www.uptodate.com/home. Accessed Aug. 7, 2015.
- AskMayoExpert. Prenatal screening: Types of screening tests. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2015.