What is a quad marker screen?

The quad marker screen is a blood test that gives a woman and her healthcare provider useful information about her pregnancy. The quad marker screen must be performed between the 15th and 20th week 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). Neural tube defects occur in 1 or 2 out of every 1,000 births. The quad marker screen can detect approximately 75% of open neural tube defects.
  • Genetic disorders such as Down syndrome, a chromosomal abnormality. Approximately 1 in 720 babies is born with Down syndrome. The quad marker screen can detect approximately 75% of Down syndrome cases in women under age 35 and 85 to 90% of Down syndrome cases in women age 35 years and older.

When should a quad marker screen be done?

A quad marker screen may be offered to you by your healthcare provider between 15 and 20 weeks of pregnancy, counting from the first day of your last menstrual period.

Do I need to have the quad marker screen?

We recommend that all pregnant women have a quad marker screen, but it is your decision whether or not to have the test. However, if you have any of the following risk factors, you may want to strongly 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.

If you have any questions or concerns about this test, please talk with your healthcare provider.