ABO blood group system each parent; each has a 25% chance, but some occur more than once. Historically, ABO blood tests were used in paternity testing, but in 1957 only 50% of American men falsely accused were able to use them as evidence against paternity. Occasionally, the blood types of children are not consistent with expectations—for example, a type O child can be born to an AB parent—due to rare situations, such as Bombay phenotype and cis AB. The A blood type contains about 20 subgroups, of which A1 and A2 are the most common (over 99%). A1 makes up about 80% of all
Hh blood group Hh blood group The h/h blood group, also known as Oh or the Bombay blood group, is a rare blood type. This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y. M. Bhende in 1952. It is mostly found in India, Pakistan, and Iran. The first person found to have the Bombay phenotype had an interesting blood type that reacted to other blood types in a way never seen before. The serum contained antibodies that reacted with all red blood cells' normal ABO phenotypes. The red blood cells appeared to lack all of