posted
Okay, here is a question I got curious about. I asked my doctor, who is otherwise pretty cool, but in this instance really pushed my buttons by telling me I was thinking too deeply.
I am Rh negative, A negative to be exact. My husband is A positive. This basically means that I get a shot with every pregnancy so that I don't develop antibodies to the Rh protein marker on blood cells. So husband and I were talking about antibodies and germs, and blood proteins and stuff like that one night. And it occured to me that pregnant ladies with O type blood don't get shots to not develop antibodies to the A or B factors, nor do people with A type blood get shots for B type blood, and the reverse. And yet aren't those protein markers more important in compatibility than the Rh factors?
Does anyone know the answer to this question?
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posted
I am also rH negative - O negative in fact. My exhusband had A negative blood. I did get rhogam after the birth of my second daughter who has A negative blood. But it was a Navy hospital and they were idjits.
ABO incompatibility is not as serious as Rh incompatibility as I recall, but I can't really remember why now... But of my 6 children, 3 were O negative and 3 were A negative, and I was only given rhogam the one time...
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posted
According to this link the A&B proteins are too large to pass the placenta and that is why there is not as much of a risk... I've never heard that before, and I'm not sure of the veracity of the site tho.
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posted
Nope. O means no protein is present; A means there is one type, and B another. A type-O mother's immune system recognizes A and B proteins as foreign invaders, and produces antibodies to kill 'em.
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posted
No, because it's the mother's blood that's making the antibodies that cause the problems. A person with A or B type blood can recieve O type blood with no ill effects, but not the other way around.
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posted
There are several different classes of antibodies. The placenta allows passage of IgG antibodies which can bind the Rhesus protein on red blood cells. ABO agglutination is caused by IgM binding. As IgM antibodies do not cross the placenta there is no problem with incompatible blood types.
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posted
[to mauibabe] Actually, type-specific blood is preferred to type-O blood -- when possible. The side-effects of an A, B, or AB getting type-O are minor, not non-existent.
And there are some rare individuals with other, less common blood-protein incompatibilities, who cannot be given type-O blood at all.
posted
Yeah, I kind of knew that, and there are other blood proteins that we don't even test for... (or did you say that too?) Blood tranfusions are risky no matter how you look at it, but if your only other option is to bleed to death, you take what you can get. Posts: 2069 | Registered: May 2001
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posted
I thought the blood mixing only occured during birth itself. That's why you get one shot prior to delivery, right? I'm curious to understand exactly what does happen. But I thought the placenta was a complete barrier against all antigens, otherwise the baby would be like a massive exogenous transplant, and be quickly rejected by the mother's immune system. I thought that only during birth itself is there some mixing of the blood, and the mother might therefore form antibodies against the baby's blood which could persist and cause complications with future pregnancies. Did I misunderstand the explanations above? (Probably so!)
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posted
So it's not the antiGENS that cross the placenta, it's the antiBODIES? Those are just large molecules, right? As opposed to the antigens which would have to be carried on actual cells? Is that the difference?
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posted
I'm going to try and do this off the top of my head...
The first baby will be born fine, but during the delivery, the baby's blood will mingle with the mother's blood. The mother's immune system will develop antibodies to the rhesus factor.
Then when the second baby is developing, if that baby is also +, the antibodies that can pass the placenta will do so, and harm the fetus.
The rhogam shot is designed to interfere with the baby's + antigen from connecting with the mother's immune system.
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posted
antigens are the bits of protein that are seen as foreign by the body's immune system.
antibody is the immune system protein your body makes to combat the antigens. An antibody matches an antigen, lock and key. There are five classes of antibodies (IgG, IgA, IgM, IgD, IgE) that act differently.
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posted
This is fascinating to me. I have A - blood, and didn't hear about any of this rh business until I was reading the Americal Medical Association Family Health Manual at the age of 12. Then it really freaked me out. I went running to my Mom demanding an explanation. "Mom! My offspring are going to die!"
Why did this come into being? Did people have problems with this in years past, or was it just considered normal for some women to only have one child that survived?
quote:This reaction doesn't always occur and is less likely to occur if the child carries either the A or B antigen and the mother does not. In the past, Rh incompatibility could result in stillbirth or death of the mother. Rh incompatibility was until recently the most common cause of long term disability in the United States. At first, this was treated by transfusing the blood of infants who survived. At present, this affliction can be treated with certain anti-Rh(+) antisera, the most common of which is Rhogam.
So, sorry to make it sound like it happens to every baby after the first, though I have no clue how often it occurs (obviously trials would be unethical).
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quote:Rh incompatibility can occur by 2 main mechanisms. It can occur when an Rh-negative mother is exposed to Rh-positive fetal erythrocytes secondary to fetomaternal hemorrhage during the course of pregnancy from spontaneous or induced abortion, trauma, invasive obstetrical procedures, or delivery. Rh incompatibility also can occur when an Rh-negative female receives a blood transfusion that contains Rh antigens.
The most common cause of Rh incompatibility is exposure to an Rh-negative mother by Rh-positive fetal blood during pregnancy or delivery, whereby erythrocytes from the fetal circulation leak into the maternal circulation. After a significant exposure, alloimmunization or sensitization occurs, and maternal antibodies are produced against the foreign Rh antigen.
Once produced, maternal Rh immunoglobulin G (IgG) antibodies may cross freely from the placenta to the fetal circulation, where they form antigen-antibody complexes with Rh-positive fetal erythrocytes and eventually are destroyed, resulting in a fetal alloimmune-induced hemolytic anemia. Although the Rh blood group systems consist of several antigens (eg, D, C, c, E, e), the D antigen is the most immunogenic; therefore, it most commonly is involved in Rh incompatibility.
Pathophysiology: The amount of fetal blood necessary to produce Rh incompatibility varies. In one study, less than 1 mL of Rh-positive blood has been shown to sensitize volunteers with Rh-negative blood. Conversely, other studies have suggested that 30% of persons with Rh-negative blood never develop Rh incompatibility, even when challenged with large volumes of Rh-positive blood.
...
The risk and severity of alloimmune response increases with each subsequent pregnancy involving a fetus with Rh-positive blood. In women who are prone to Rh incompatibility, the second pregnancy with an Rh-positive fetus often produces a mildly anemic infant, whereas succeeding pregnancies produce more seriously affected infants who ultimately may die in utero from massive antibody-induced hemolytic anemia.
...
[Note that ABO incompatibility is protective because it leads to destruction of the fetal cells often before they can sensitize the mother:]
The incidence of Rh incompatibility in the Rh-negative ABO incompatible mother is reduced dramatically to 1-2% and is believed to occur because the mother's serum contains antibodies against the ABO blood group of the fetus. Fetal erythrocytes apparently are destroyed in the maternal circulation before Rh sensitization can proceed to a significant extent. ... [The numbers:] Rh sensitization occurs in approximately 1:1000 births to Rh-negative women. The Southwest US has an incidence approximately 1.5 times the national average, which likely is caused by immigration factors and limited access to prenatal care. Only 17% of pregnant women with Rh-negative blood who are exposed to Rh-positive fetal blood cells ever develop Rh antibodies.
[ December 17, 2004, 06:03 AM: Message edited by: Sara Sasse ]
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posted
I'm O+, my children and their father are all A+. No Rhogam anywhere because no (type) neg issues, but all kids were jaundiced at birth. I was told by the nurses at the hospital that this was directly related to the different blood types. Heather - my eldest - was the worst affected and spent 4 days under bilirubin lights before she could go home and then had home healthcare nurses coming out twice a week to check on her and make sure things were still going okay. Hannah (the first of two surrogates) also spent time under lights but nowhere near as much.
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quote: I'm going to try and do this off the top of my head...
The first baby will be born fine, but during the delivery, the baby's blood will mingle with the mother's blood. The mother's immune system will develop antibodies to the rhesus factor.
Then when the second baby is developing, if that baby is also +, the antibodies that can pass the placenta will do so, and harm the fetus.
Speaking from 2nd hand experience, I think this is how it works.
My Dad has a weird thing with his blood type -- He's type Ac or A with little c. So he and my mom have four normal kids, one of whom we assume also has Ac because when #5 (me) comes along, there are problems with Mom's antibodies fighting off my blood cells. I don't think it was a huge problem until after I was born... after they took me home I was jaundiced and had to go back to sit under the lights.
With my little brother (#6, probably #3 with Ac) there were significantly more problems. They ended up doing a C-section about a month early, he had severe jaundice, and Mom was having various problems.
I think my mom's OBGYN ended up writing something about this Ac phenomenon in a book with my family as the main example... Posts: 4089 | Registered: Apr 2003
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posted
Thanks for the info. I knew all of it about Rh incompatibility, but now I know why ABO incompatibility is not much of a problem.
But let me summarize to make sure I understand correctly. Basically, the antibodies for A and/or B proteins are too big to pass easily through the placenta, but the antibodies for Rh can pass through. Sweet. I always think it is so fantastic how our bodies work.
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posted
Sorry, I didn't mean that the only effect was jaundice, those were just the ones that I remember hearing about. Mostly it was my mom that got really sick with me and my little brother, but other than the jaundice we seem to be just fine (normal brain/physical develpment, etc.).
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