There was yahoo groups for rh neg. people. the groups claim its from aliens because it can't be traced to genetic origin like others
Problems with the Rh factor occur only when the mother's Rh factor is negative and the baby's is positive.
Why is Rh disease a concern?
When an Rh negative mother has a baby that is Rh positive, problems can develop if the baby's red blood cells cross to the Rh negative mother. This usually happens at delivery when the placenta detaches. It may also happen, however, anytime blood cells of the two circulations mix such as during a miscarriage or abortion, with a fall, or during an invasive prenatal testing procedure such as an amniocentesis or chorionic villus sampling.
The mother's immune system sees the baby's Rh positive red blood cells as foreign. Just as when bacteria invade the body, the immune system responds by developing antibodies to fight and destroy these foreign cells. The mother's immune system keeps the antibodies in case the foreign cells appear again, even in a future pregnancy. The mother is now Rh sensitized. http://www.healthsystem.virginia.edu/uvahealth/peds_hrpregnant/rhdiseas.cfm