The Rhesus factor, often abbreviated as Rh factor, is a protein that can be present on the surface of red blood cells. If a person has this protein, they are considered Rh-positive; if they lack it, they are Rh-negative. This factor is important in blood transfusions and pregnancy, as mismatches can lead to serious health issues. The Rhesus factor is inherited from parents, and its presence or absence is determined by specific genes. Understanding one's Rh status is crucial for safe medical procedures, especially for individuals with blood type concerns or those planning to become pregnant.