Why Rh Incompatibility is worse than ABO incompatibility? - USMLE Forums
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Old 03-10-2012
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RBC Why Rh Incompatibility is worse than ABO incompatibility?

Goljan mentions that anemia in newborn due to Rh incompatibility is more severe than in ABO incompatibility.
I was wondering that in both causes, reason for anemia is the same...extra-vascular hemolysis.

So why anemia in Rh incompatibility is more severe than in ABO incompatibility ?
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Old 03-10-2012
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Maternal ABO antibodies are IgM and cannot cross placenta. Hemolysis due to ABO incompatibility occurs in isolated cases where the mother happens to have Anti A/B IgG.

Please correct me if I am mistaken.

Cheers
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Quote:
Originally Posted by xpabhishek View Post
Maternal ABO antibodies are IgM and cannot cross placenta. Hemolysis due to ABO incompatibility occurs in isolated cases where the mother happens to have Anti A/B IgG.

Please correct me if I am mistaken.

Cheers
Absolutely correct, it's even mentioned by Dr. Goljan in his audios.
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Old 03-10-2012
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Absolutely correct abhishek but one thing i wanna add about Rh incompatibility is that it may also lead to Abruptio Placentae which can cause a still birth. Corrections appreciated
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Another explanation is that expression of A and B aglutinogens is low at birth (they mature as the child grows) so the immune response isn't very intense.
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Quote:
Originally Posted by xpabhishek View Post
....Hemolysis due to ABO incompatibility occurs in isolated cases where the mother happens to have Anti A/B IgG.
@ xpabhishek

even in those situations, hemolysis due to ABO is less severe than Rh incompatibility.

for eg, goljan gives eg of mother having O blood group and baby having A group. then there he mentions, ABO incompatibility is less severe than Rh.
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Quote:
Originally Posted by LatinGeorge View Post
Absolutely correct, it's even mentioned by Dr. Goljan in his audios.
really?
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Old 03-14-2012
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Hey, i looked up Goljan.
It appears that people with O blood group do have anti A & B IgG Ab in addition to the IgM ones.

The actual answer to your question is that in case of combined ABO & Rh incompatibility the fetal RBCs from fetomaternal bleeds get destroyed immediately. Hence mother doesn't get sensitized against Rh+ Ag.

Please go through Goljan chap 15 to get a more clear idea on the topic.
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Also the ability to cause hemorrhage is greater for anti D IgG than for anti AB IgG.
xpabhishek: when is your date?
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