Rh and ABO
Name: Pamela C.
I am Rh negative, and my husband is Rh positive, so when
I became pregnant, I became interested in Rh incompatibility. Neither my
obstetrician nor any of the medical books or hematology web sites I have
looked at could answer the following: Why is ABO incompatibility less
serious than Rh incompatibility? They are both just proteins on red blood
cells that you can develop antibodies to, right? So why are the results
of incompatibility so different? It is fine to give a technical answer.
I am a registered Medical Technologist and I got out my Immunohematology text
(blood banking). I could find no real good answer either. There were some
hints, however. You probably know that the first child born to an Rh- mom
and Rh+ dad usually shows no symptoms because the baby's blood cells are what
is causing the mom to form antibodies. This usually does not happen until
birth, when the placenta detaches and the mom's and baby's cells can mix. If
you get anti-immune globulin ("the shot") within so many hours after birth
this can find the baby's cells and inactivate them before your body knows
they were there.
If this does not happen and you make antibodies to the
baby's blood, your second child could be affected. You probably also know
that if your husband is heterozygous (Rh+/Rh-) there is a 50% chance that
each baby will be negative also. As far as why Rh is worse than ABO, what is
your blood type? If you are type O, you have both anti-A and anti-B
antibodies and there could be a reaction if the baby's cells mix with yours.
There is also a possibility of ABO incompatibility between you and a child if
you are, say, A and the baby is B. It does cause a mild hemolytic anemia in
the baby, but I am told that a few days under the bilirubin lights usually
takes care of this. Sorry I could not be of more help.
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Update: June 2012