How does the AFP triple screen (AFP3 or Downscreen Plus) work?
In addition to measure the levels of alphafetaprotein in the bloodstream, the AFP3 test also measure the levels of human chorionic gonadotropin (HCG) and unconjugated estriol. HCG is present in every pregnancy, and is used to determine whether you are pregnant (remember your home pregnancy test?). HCG is created by the placenta, and abnormally high values have been seen in Down’s syndrome pregnancies. Unconjugated estriol is a hormone that is synthesized by your baby’s liver, the placenta and the adrenal glands. Unusually low levels have been found in Down’s syndrome pregnancies. Low levels are also found in other pregnancies with a high somatic chromosome count.
