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Rhesus Incompatibility Disease


(Rh Disease)




What is Rh Disease and what causes it?


Everyone is born with a specific blood type and an RH factor.  For example, you may have blood type "A" with an Rh factor of "positive" (A+). This blood typing stays with you for life.


For full details on blood types, please seek information on Blood Typing elsewhere.  


In 85% of people, the Rhesus Factor is positive (Rh+).  For the other 15%, the Rh factor is negative (Rh-).


If a woman has Rh-negative blood and the man has Rh-positive blood, then it is possible for problems to arise.  


Note: Rh Disease can only occur in women that have Rh Negative blood.


Note: If both the mother and baby are Rh negative, then there is no risk.


Note: If both the mother and natural father are Rh negative, then there is no risk because the child must also be Rh negative. However, most doctors prefer to presume that all Rh-negative women are at risk and will treat her accordingly.


If an Rh-negative woman has a baby that is Rh positive, then it is possible for some of the baby's blood to enter into her system.  This can happen under several circumstances:


          During the birth, 

          Naturally (between 28 weeks and delivery), 

          During an amniocentesis, 

          At an abortion,

          When a miscarriage occurs.

If the baby's Rh positive blood enters a mother who is Rh Negative, then her immune system sees the cells as 'incompatible' or 'foreign' and will subsequently produce anti-rhesus antibodies to try to destroy them for her own self-protection.


This may not seem like a big problem, however, if she has another pregnancy where the baby is Rh positive, then these antibodies that have formed will pass into the baby's bloodstream via the placenta and attack the red blood cells of the baby.


Once these naturally created anti-rhesus antibodies are present in the mother's bloodstream, they will remain for life in the same way as antibodies for other diseases: chicken pox for example.