WOMENS-HEALTH Messages for November, 1999: Re: ABO incompatability for JClark

Re: ABO incompatability for JClark

From: Christine (anonymous@obgyn.net)
Fri, 5 Nov 1999 08:00:59 -0600 (CST)

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In reply to: JHC: "ABO incompatability for Christine Smith"

At Thu, 04 Nov 1999, JHC wrote: >
>Christine,
>Thank you for responding to my question regarding ABO incompatability.
>You asked in your response if my egg donor had a type and Rh done prior
>to the in-vitro cycle. The answer is yes, but when the donor list was
>made available to me, it was not on there. When I inquired about blood
>type incompatabilty prior to the embryo transfer I was told that it
>should not be a problem. I am Rh positive and I assume that they
>figured I could not be desensitized to an antibody that I already had. I
>just read Bryce's post and your response to it about anti little C. When
>I was questioning my son's pediatrician about ABO incompatability he
>mentioned something regarding that the incompatability could have been
>ABO or someother antibody factor. He went on to say that in 20 years of
>practice he only had to transfuse 1 baby due to a severe
>incompatability. I assumed that may have been a missed Rh
>incompatability. I have been told by several sources that ABO
>incompatability is merely and inconvience, and with swift treatment and
>close following it usually works out o.k. Am I correct in assuming the
>incompatablility is on the part of the infant's system and not mine, and
>with an Rh incompatablity the incompatability is on the part of the
>mother? Hematology has never been my strong point.
>Thank you for your informative responses.
>
>Respectfully,
>JClarke

Hi! I should read all the posts before responding. But it was 1 am last night and I couldn't tackle this one when I got to it. :<) You are right-most of the time ABO incompatibility is just a nuisance. The baby gets lots of blood tests (in the "old" days we stuck their little heels over and over again, sure hope they have come up with something better than that now), gets put under the lights with little masks on, and there is a lot of anxiety, as you found out, even continuing as you have to take the baby in for periodic checks after you go home. But I guess every now and then there is a bigger problem, which your doctor was referring to. It is unusal with ABO incompatibility. These days there should never be a case of missed RH incompatibility due to the most common factor, D. I guess it could happen if there was a series of blood typing errors, the mother not recognized as RH negative, etc but this really shouldn't happen. As in the case of Bryce though, antibodies for the other RH factors (which are c,C,e,E) could be missed but would probably be thought of when problems started arising. This wouldn't usually happen if antibody screens were done on all pregnant women, not just RH negative ones. The genetics behind these blood factors gets a little complicated. Simply put, RH "positive" women (the term "positive" is referring to only one of the factors, D) can make antibodies against the other factors of the RH system, e,E,c,C. Looking a table of statistics among the general population, 14% will be what is called "RH Negative". This group is negative for all the RH factors and would be typed as cde/cde. However there are a very small percentage of people who are also RH "negative" who would type as Cde/cde or even rarer Cde/Cde, and cdE/cde and cdE/cdE. Because they lack the D factor, they type as RH negative, (because in the standard RH typing test they are only testing for "D") but if the person who is cde/cde received blood from one of these other RH "negative" groups, that person could form antibodies against the other factors he/she lacks, such as (big)C and (big) E. All of this is possible, not just in pregnancy, but in transfusion situations, in both RH "negative" and RH "positive" patients. Then there are a lot of other factors besides the RH ones-Kell, Duffy, etc etc. All of these can cause incompatibilities after repeated exposure which is why the danger in receiving blood transfusions is not just because of disease! This doesn't happen too often though, unless you are unlucky and are one of those rare groups and receive blood from one of the common groups. When you receive a blood transfusion, in most cases you are not typed for these other RH factors, because of these statistics. You are typed for your ABO group and whether or not you are "D" positive or "D" Negative. You would also have an antibody screen on yourself done, and then a crossmatch with the donor blood cells and your serum (which would contain the antibody if present) The antibody screen would pick up any antibodies against these other factors and THEN they would test the donor cells to make sure they did not contain the corresponding factor. They would not rely on the crossmatch to show this as sometimes reactions occur in the body that do not show up in the tests. It is complicated! I have gotten off on a tangent. To answer your last question, the mother's immune system forms the antibodies against factors she doesn't have but are present in the baby. The reaction is in the baby. The antibodies don't hurt the mother. The ABO and the RH incompatibilities are a little different. With ABO, it often happens with the first baby, but is not (usually) as serious. With RH (and the other factors such as Kell)usually the first baby is okay (unless the mother haas been previously "sensitized" through transfusion or previous pregnancy/miscarriage). Later babies have the problem. But it doesn't always happen-even in the "old days" RH incompatibility didn't always happen when it should have.

Chris S.

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