Meaning of Rh factor

Rh fac•tor

Pronunciation: (är'āch' fak"tur), [key]
— Physiol. Physiol.
  1. any of a type of specific antigen present on the surface of red blood cells, persons having inherited such antigens being designated Rh+and persons lacking them, a much smaller group, being designated Rh−blood of Rh− persons is incompatible with Rh+ blood because of antibody reaction, and an Rh− woman who bears an Rh+ baby will have formed antibodies to the fetal blood that, unless removed from her bloodstream by apheresis in a subsequent pregnancy, will be carried across the placenta and destroy red blood cells of the next Rh+ fetus, resulting in erythroblastosis in the newborn.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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