By screening the blood of the pregnant woman, 60% to 75% of all genetic diseases of unborn children can be recognized before birth. The AFP-plus-test is conducted in about the 17th week of pregnancy and measures the levels of oestriol, Beta-HCG and alpha-fetoprotein.
With the first trimester screening, up to 90 of children's illnesses can be recognized. The results of the mother's blood concerning levels of free Beta-HCG and PAPP-A are compared with the results of the embryo's neck fold.
If the result indicates an increased risk, a puncture of the amniotic liquid (amniocentesis) is conducted, as this is a more precise method.