Definition of Quadruple screen test:

The quadruple screen test is a blood test done during pregnancy to determine whether the baby is at risk for certain birth defects.

How the test is performed:

This test is usually performed between the 15th and 22nd weeks of the pregnancy, but it is most accurate between the 16th and 18th weeks.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

The blood sample is sent to a laboratory for testing.

The test measures levels of four substances:

• 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 age
• Your ethnic background
• Your weight
• Your babyâ ' s gestational age

How to prepare for the test:

No special preparation is necessary.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

To find out if your baby might be at risk for certain birth defects, such as Down syndrome and neural tube defects.