The Quad marker screen is a blood test that provides a woman and her health care provider with useful information about her pregnancy. The quad marker screen must be performed between the 15th and 20th weeks of pregnancy. During the quad marker screen, a sample of blood is taken from the woman's vein. Substances in the blood sample are measured to screen for:

  • Problems in the development of the fetus' brain, spinal cord and other neural tissues of the central nervous system (neural tube).Problems with neural tube development can occur as spina bifida or anencephaly (absence of all or part of the brain). The quad marker screen can detect approximately 75 percent of open neural tube defects.
  • Genetic disorders such as Down syndrome, a chromosomal abnormality.

What substances are measured during a quad marker screen?

  • Alpha-fetoprotein (AFP) -- a protein produced by the fetus' liver
  • Unconjugated Estriol (UE) -- a protein produced in the placenta and in the fetus' liver
  • Human Chorionic Gonadotrophin (hCG) -- a hormone produced by the placenta
  • Inhibin-A -- a hormone produced by the placenta

We recommend that all pregnant women have a quad marker screen, but if you have any of the following risk factors, you may strongly want to consider having the test:

  • You are age 35 or older when the baby is due
  • Your family has a history of birth defects
  • You've had a child with a previous birth defect
  • You have had insulin-dependent (type 1) diabetes prior to your pregnancy