The absence of Rh factor refers to the absence of genetically determined antigens present on the surface of red blood cells, which can trigger immune responses. In the case where an Rh-negative woman is carrying an Rh-positive fetus, her body may generate antibodies against the fetus’s blood, leading to a condition known as Rh disease. Sensitization to this disease occurs when the woman’s blood comes into contact with the blood of the fetus. To prevent sensitization to Rh disease, an Rh immune globulin vaccine called RhoGAM must be administered to a woman after an abortion, miscarriage, or prenatal tests.