Simple blood test. Antibody screening during pregnancy is essential to identify blood group and antigen incompatibilities that might be exist between a mother and her developing child. The screen involves determining the mothers blood group type: a, b, ab, o and rh status (pos and neg). About 10 percent of caucasian women (much lower in non-caucasian ethnicities) are rh negative entering pregnancy.
Blood typing. Rh is a protein found on red blood cells (rbc's). Rh screening is used in blood typing. If the protein is found on rbc's than it is termed rh positive. 85% of people are rh positive. "a" positive blood is blood type a with a positive rh factor. Rh factor is important to newborns. If an rh negative mom gives birth to an rh positive baby then the mom may make antibodies to the baby's blood.