Important Information on Blood Types of Parents and Children
March 28, 2012 174 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.
Please read the facts in red text, and click on the red links and read the information there, before asking questions in the comments. I am not a doctor or any kind of expert on blood types, just an ordinary person who wrote an article to publicize information that I felt was not clearly enough presented to the general population.
UPDATE: Since I posted this article, I’ve seen that many of the people who read it are looking for information about which blood types can have children together. Aside from rare mutations, a woman of any blood type and a man of any blood type can have a healthy baby together.
If the mother’s and father’s blood types are the same, this does NOT harm the baby.
In repeated Internet searches over three years, I have never found any report of any problem caused by parents having the same blood type–I have only seen people worrying about this possibility. There is no reason to worry! If you want to know what blood type your baby might have, or if you are wondering how your blood type can be different from your parent’s, look at these handy tables. Now, back to our story!
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! When my only sibling made his first blood donation a few years later, we learned that he also is Type O. Luckily, neither of us ever has needed a blood transfusion anyway.
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. This article also explains why a breastfed baby who develops jaundice does not need to be given formula.
UPDATE: While pregnant with my second child, I was given the 2013 revised edition of The Baby Book by William & Martha Sears. It now includes a thorough explanation of newborn jaundice and its causes. Thank you, Dr. Sears! Lydia also became jaundiced a few days after birth (and a few days before she started spitting up blood–it was quite a week!) but instead of going to the NICU, she was treated at Children’s Hospital in a regular inpatient room, where I was allowed to sleep in the room with her and feed her whenever she was hungry, and they didn’t give her any drugs. It was a much better experience for both of us! She recovered just as well as her brother without drugs.
If you have a choice, ask for jaundice treatment at home using a bili blanket. If your baby’s jaundice requires more intense phototherapy and/or 24-hour monitoring, ask for your child to be admitted as a regular inpatient in a children’s hospital rather than to the NICU at a maternity hospital. You’ll be more comfortable, and it will be less expensive for you and/or your insurance. Also, ask to be informed of any drug that is administered to your child, and ask why it is being given.