Triple and Quad Screening

Triple or Quad marker screening tests involve measurements of levels of certain hormones and proteins in a pregnant woman's blood. These tests should be performed between the 15th and 20th week of pregnancy. The substances measured include proteins and hormones produced by the fetus.

Triple Marker Screening:

• Alpha-fetoprotein (AFP) - a protein produced by fetus' liver
• Unconjugated Estriol (UE) - a protein produced in the placenta and in the fetus' liver
• Human Chorionic Gonadotropin (hCG) - a hormone produced by the placenta
• Inhibin A - a hormone produced by the placenta (measured with the above in the "Quad" screen

These screening tests help identify women whose unborn babies may have certain problems in the development of the fetus' brain, spinal cord and other neural tissues of the central nervous system (neural tube). A defect in the neural tube (NTD) can occur as spina bifida or anencephaly (~1 to 2 out of every 1000 births). The tests can also be used to screen for genetic disorders such as Down syndrome, a chromosomal abnormality.

The expected amounts of these substances normally found in the mother's bloodstream changes each week of pregnancy. Higher than normal AFP levels could indicate that the fetus has an open (without the skin covering) NTD or an abdominal wall defect. Lower than normal AFP levels could indicate that a woman is at higher risk for having a baby with Down syndrome. Levels of hCG and Inhibin-A are higher than normal and levels of Unconjugated Estriol are lower than normal when a woman has an increased risk for Down syndrome. The "Quad" marker detection rate for Down syndrome is about 78-80% overall and 85-90% for women 35 and older.

When these screening tests are abnormal, women should be offered more detailed counseling, more detailed ultrasound imaging and possibly additional tests (e.g. amniocentesis). This is a common reason for referral to a Maternal-Fetal Medicine specialist.

More information from the Children's Hospital of the King's Daughters

This information is not intended to substitute or replace the professional medical advice you receive from your physician. The content provided on this page is for informational purposes only, and was not designed to diagnose or treat a health problem or disease. Please consult your physician with any questions or concerns you may have regarding a medical condition.