Important Information on Blood Types of Parents and Children
March 28, 2012 87 Comments
There are two important facts about the blood types of parents and their children that are not widely known. One of them caused an unexpected health problem in my family, and the other could have caused a much more serious problem but didn’t.
No, I’m not talking about Rh factor. The issue of “positive” vs. “negative” blood and how it affects pregnancy is well-known and mentioned in most books about pregnancy. Here is a typical article about Rh factor. Notice how it mentions antigens–the “letter” aspect of blood type, A, B, AB, or O–but then moves on, as if antigens aren’t important.
What most people know about antigens is that they are important if you are receiving a blood transfusion. Putting blood with A antigens into your body, if your own blood does not have A antigens (Type A or AB), will cause an immune response that can kill you. The same is true for B antigens. If you are Type O, both A’s and B’s are dangerous, so you should not receive a transfusion of any type other than O. It is pretty quick and easy for medical professionals to determine a person’s blood type, so we don’t need to worry a whole lot about being given the wrong kind of blood, but just in case, it’s a good idea to know your blood type.
These are the two things I didn’t know until after the point when it would have been medically useful to know them:
1. If both parents have the same blood type, that does not mean that all of their children also have that blood type. (Any doubts I had about this being a poorly-understood fact were erased when I searched for a good online reference and found mostly discussion boards where people were confused about it! Even some authoritative medical sources had explained the issue in a confusing or incomplete way.) Here is a good explanation of how blood types are inherited. The only sure thing is that if both parents are Type O, all their children will be Type O. For the other types, there are other possibilities.
When I was about eight years old, my mother bought metal identification tags for my brother and me to wear when we were playing or bike-riding away from home, just in case we had an accident and were unable to tell rescuers our vital information. My tag stated my name, address, telephone number, and “Blood Type A+”. This was the first I had ever heard of blood types, and I asked if this meant I had the best type of blood. :-) My mom explained about antigens and transfusions. I went about my adventures, convinced that if I should ever need a transfusion, the doctors would read my tag and give me the right type of blood.
When I was sixteen, I donated blood for the first time. I saw the Red Cross person write “O+” in the “blood type” box on the form. I objected, “No, I’m A Positive.” She said, “No, you’re not. I just tested your blood.” My emotional turmoil over whether I had been switched at birth or something was cut short by my friend Don, a future doctor who was a volunteer helping to run the blood drive, explaining to me that the A’s and B’s of blood type are dominant genes, so two parents with Type A blood may have genotype AO (one A gene and one O gene) and therefore have a 1 in 4 chance of having a child with genotype OO and therefore Type O blood.
My mother, who has a doctorate in biology, did a lot of forehead-smacking when she heard my news! Luckily, I never have needed a blood transfusion.
2. If a mother has Type O blood, and her baby has another type, the baby is likely to develop a dangerous level of jaundice after birth. I do not understand why this fact is not in every pregnancy book, right alongside the topic of Rh factor! I guess it’s because jaundice is easy to notice (baby’s skin turns yellow) and relatively simple to treat (expose baby to lots of ultraviolet light and give extra fluids), and there’s nothing you can do to prevent it. Still, it would have been really nice to be informed of this possibility before my son was born because then I would have read about jaundice treatments and felt sure that the hospital was doing the right thing. As it was, I just had to trust them. Nicholas spent 24 hours in the neonatal ICU being bombarded with blue lights from three sides, receiving IV fluids and medication (I’m still not really sure that all that medication was such a good idea–the hospital didn’t tell us they were giving him anything other than water and electrolytes; we didn’t know until I received my itemized bill weeks later, and we never got to talk with a doctor about why those drugs; we only Googled them), getting a blood test every 6 hours, allowed to be held only for 10-20 minutes every 3 hours when I was nursing him, and that was traumatic for both of us! I wish I had been prepared. Here is some basic information on newborn jaundice, including an explanation of blood type incompatibility.
I hope this information is helpful to other families! Knowing it earlier would have worked for me.