What is the quad screening for birth defects?

The quad screening is a blood test that may be done at 15 to 22 weeks of pregnancy. It's used to look for possible problems with your baby. The quad screening measures the amounts of four things in a pregnant woman's blood. They are:

• Alpha-fetoprotein (AFP). AFP is made in the liver of an unborn baby (fetus).
• Human chorionic gonadotropin (hCG). This hormone is made by the placenta when a woman becomes pregnant.
• Estriol (uE3). This is a form of estrogen that increases during pregnancy. It's made in large amounts by the placenta.
• Hormone inhibin A. This hormone is produced by the baby and the placenta.

This test can't show for sure that your baby has a birth defect. You would need a diagnostic test called amniocentesis to find out for sure if there is a problem.

Why is the test done?

The quad screening is done to find out the chance that your baby has certain birth defects, such as Down syndrome, Trisomy 18, spina bifida, or anencephaly.

How is the test done?

A health professional uses a needle to take a blood sample, usually from the arm.

What happens after the test?

If you have a positive test result for Down syndrome or Trisomy 18, your doctor may give you the option to have an amniocentesis to find out for sure if there is a problem. But it's your choice whether to have another test. If you have a negative result, amniocentesis is not indicated. A positive result for spina bifida is following up by a detailed anatomy ultrasound.