Reply #5: The rough and ready definition of a species is a genetically isolated breeding population. [View All]

[okasha]

O negatives can breed successfully with A+, B+, AB+, O+, A-, B-, AB- and other O-'s; in fact, any combination of two types can produce viable offspring. Medical caution and possibly preventive measures are indicated, though, when an Rh- mother is carrying an Rh+ baby. There are circumstances under which some of the baby's blood can get into the mother's system, and the foreign Rh+ factor will produce an antibody cascade. If it's heavy enough, it can attack the baby and cause hemolytic anemia. (That may be where the notion of separate species comes from.) This used to result in so-called "blue babies" born with oxygen deficiency. But there are now treatments that can get mother and baby both successfully through the pregnancy.