The Rh factor, or Rhesus factor, is a protein found on the surface of red blood cells (RBCs). People are classified as Rh-positive if they have this protein on their RBCs, and Rh-negative if they do not

. It is an inherited trait, passed down from biological parents

. The Rh factor is important in blood typing and compatibility. Blood types are commonly categorized by the presence or absence of A and B antigens and the Rh factor, resulting in types such as A positive, O negative, etc.

. The Rh factor is especially significant in blood transfusions and pregnancy. For transfusions, Rh-positive individuals can receive both Rh-positive and Rh- negative blood, but Rh-negative individuals should only receive Rh-negative blood to avoid immune reactions

. During pregnancy, Rh incompatibility can occur if an Rh-negative mother carries an Rh-positive fetus. This can cause the mother's immune system to produce antibodies against the fetus's red blood cells, potentially leading to complications. Medical interventions are available to manage this condition

. Scientifically, the Rh factor corresponds mainly to the Rh(D) antigen, which is the most immunogenic among the Rh antigens

. Beyond its role in blood compatibility, recent research suggests that Rh proteins may help transport ammonium, a toxic metabolic by-product, and help maintain blood pH balance

. In summary, the Rh factor is a key protein on red blood cells that determines Rh-positive or Rh-negative blood type, critical for safe blood transfusions and pregnancy management