An ABO test involves drawing a small sample of your blood from a vein—usually in your arm. Lab professionals will mix your ...

Ever wondered why some people's blood groups are positive and others negative? It’s all got to do with the Rh factor on your blood cells. Rh factor, or the Rhesus factor, is an antigen.

Maternal-infant ABO blood group incongruence was associated with reduced risk for severe infection among second-born infants.