If a woman is already at an increased risk of having a baby with one of these problems, she may be offered the diagnostic test first rather than having the screening test. It is present in amniotic fluid, fetal blood, and, in smaller amounts, in the woman's blood. The AFP test is usually performed at 15-20 weeks of pregnancy. This is when the test is most accurate. For the test, a small amount of blood is taken from a vein in the woman's arm.
Results are usually available in about a week.
Triple Screen Test Adding certain tests to the AFP test can give more information about your risk of having a baby with Down syndrome than the AFP test alone. This is called a triple screen test. Besides measuring AFP, a triple screen test measures other substances in the woman's blood that come from the pregnancy. Levels of hCG are higher than normal in most pregnancies with a fetus with Down syndrome. Estriol is produced mostly in the placenta and in the liver of the fetus.