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

The test is done to find out if your baby might be at risk for certain birth defects, such as Down syndrome and birth defects of the spinal column and brain (called neural tube defects).

All pregnant women should be offered this test. The quadruple screen test is normally done some time between the 15th and 20th week of pregnancy.

Certain women are at greater risk for having a baby with these defects. These women include those over 35 years old during pregnancy, those taking insulin to treat diabetes, and those with a family history of birth defects.

This test is a screening test. This means it does not diagnose birth defects. Instead, it indicates whether your baby has a higher risk of these defects.

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 pregnancy hormones:

• 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 baby’s gestational age

No special preparation is necessary.

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.