$Unique_ID{BRK01055}
$Pretitle{Pregnancy and Childbirth}
$Title{What is "Rh Incompatibility"?}
$Subject{genes pregnancy Rh factor }
$Volume{K-7}
$Log{}

Copyright (c) 1991   Tribune Media Services, Inc.


What is "Rh Incompatibility"?


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QUESTION:  We have a problem in our family that has been diagnosed as "Rh
Incompatibility" with the loss of a pregnancy in my very normal daughter who
has already had one normal, happy, healthy child.  Can you explain this
condition to us, as we are very confused by the information we have been
getting from all sides?

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ANSWER:  Understandable enough, when you consider the complexities of human
inheritance mechanisms.  Except for the sex chromosomes, we all have 22 paired
chromosomes (autosomes) that are identical in size, shape and placement of the
genes which control our inheritance patterns.  Some genes are "dominant" and
will exert their effect when present, others are "recessive" and can only act
when no dominant gene for the same trait is present on either chromosome.  If
a mother is Rh negative, she possesses two recessive genes (one on each
chromosome).  However she may bear an Rh positive baby, when the trait has
been transmitted to the child from a father who is Rh positive.  The red blood
cells (RBC) of the fetus can cross the placenta into the mother's blood
stream, provoking an immunologic response, leading to the production of
antibodies against the Rh factor by the mother's system.  When these
antibodies cross back over the placenta, they attack and destroy the RBC's of
the fetus, causing severe anemia and a condition known as "Erythroblastosis
Fetalis".  The condition can be so severe that the fetus dies in the uterus.
Since antibody production does not usually begin in earnest until after
delivery, the first baby escapes before the antibodies have developed in
quantity, and it is the second pregnancy that is affected.  The solution is to
treat all Rh negative mothers with an anti-Rh antibody preparation at about
the 28th week of pregnancy, that can destroy the maternal antibodies which
effectively eliminates her sensitivity to the fetal RBC's.  Sensitized mothers
must be carefully monitored throughout pregnancy and treatment of the fetus
may even include intrauterine transfusions when indicated.  Incidentally the
term "Rh" stands for "rhesus" for it was in that species of monkey that this
blood factor was first identified.
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The material contained here is "FOR INFORMATION ONLY" and should not replace 
the counsel and advice of your personal physician.  Promptly consulting your 
doctor is the best path to a quick and successful resolution of any medical 
problem.
