Important Information on Blood Types of Parents and Children

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.

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.

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!  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.  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!  My second child 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!

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.

I hope this information is helpful to other families!  Knowing it earlier would have worked for me.

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About 'Becca
author of The Earthling's Handbook, about the environment, parenting, cooking, and more!

98 Responses to Important Information on Blood Types of Parents and Children

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  2. Becky Brown says:

    But can a father with A+ blood and a mother with B+ blood have a child with A- blood.

  3. biggsis says:

    Very interesting. I did not know that a baby of another blood type with a type ‘O’ mother can have jaundice. We did not have to have extensive treatment – but my type A son needed some treatment. Thanks for sharing… I’m a nurse and I didn’t know that!

  4. Casey says:

    I had never read or heard of this blood incompatibility until my daughter was born either! I believe they should include this in the materials, etc. When preparing for a baby. My daughter wasn’t far from needing a transfusion & was in NICU for the first 4 days of her life. Thank God she got through it!

  5. Cassie says:

    If my mom has b+ and I have o- is that possible that I have negative blood and my mom have positive blood

    • 'Becca says:

      Yes, if you have had your blood typed (by a doctor, blood drive, etc.) and they said your type is O-, you have negative blood.

      It is possible for you to have negative blood and your mom, or even both parents, to have positive blood. Everybody has two genes for Rh factor, and if at least one of them is + you gat positive blood; it is only if both are – that you have negative blood. You get one gene from each parent. So if both parents have a + and a – they can have a child with two -. There is a nice chart explaining this in the article about how blood types are inherited.

      So don’t worry, your mom is really your mom! Merry Christmas!

  6. Loi says:

    Wow, someone has to be really living under a rock to not know that certain different blood types cant mix. Really!. Wake up!.

    • 'Becca says:

      That is why I said that what most people KNOW about blood types is that some types should not be mixed within one person’s body, in a transfusion.

      What I see in my Word Press stats on literally a daily basis (this is my most-read article ever) is that this fact has led many people to be confused about whether or not it is dangerous for people of different blood types to have children together. I am glad I can help clear up the confusion.

      • km says:

        I am o negative and so is my Hubby. Wee are expecting. I read online that because2 negatives equal a positive, that baby can be positive…? That’s not true is it? Because my dr haven’t have me the rhogam shoot because my Hubby is also o negative! Now I’m a little nervous with wondering if Red cross told my Hubby his correct blood type and if I need the shot… 2 weeks b4 due date i guess I’m nervous…thanks

        • 'Becca says:

          Talk to your doctor to make sure, but I am almost certain “two negatives make a positive” is a rule for math but not for blood types. Click on the link about how blood types are inherited for more info. Best of luck with your baby!

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  8. Holli says:

    I am O-, my husband and my 3 kids are O+. 2 of my kids suffered from jaundice; I wonder if the Rh factor contributes to that as well, as we both have O blood.

  9. Muzza says:

    Is it at all possible for a mother with A- and a father with A+ to have a child with AB+ blood

    • 'Becca says:

      I am not an expert, so please check the sources linked above…but if I understand correctly, no, a person with AB must have at least one parent who is either B or AB.

    • corie says:

      im confuse the obgyn told me my baby is ABO IVE never heard of it im RHpositive

      • 'Becca says:

        Ask the doctor what he/she meant. I have only heard “ABO” used as a shorter way to say “the aspect of blood that is A, B, AB, or O” and nobody can be all of those types at the same time. I’m not an expert!

  10. Maria Eva Choo says:

    both of my parents are blood type O and my brother and sister share the same blood type as my parents.however,I am a blood type B..What does that mesn,am I adopted?

    • 'Becca says:

      The charts I linked to do indicate that two Type O parents can only have O children. PLEASE talk to an expert before you accuse your parents of anything, though!

  11. Tuesday Mills says:

    If i have.A- blood and father has A+ is it possible to.have O- child??

    • 'Becca says:

      Yes. A and + are dominant genes. If each parent’s genes for antigens are one A and one O, you both have Type A blood, but when your genes are combined there’s a 1 in 4 chance of the child getting two O genes and therefore Type O blood. To have – blood you must have two – genes, but the father with + blood could have one + and one -, so when your genes combine there’s a 1 in 2 chance of the child getting two – genes and therefore – blood.

  12. Archismita says:

    Hi, You said you have type O blood and your son had jaundice and 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. So, it must mean your wife has type O. But, how can the child be anything but type O since you have already said that both parents with type O blood will have a type O kid? And how can the kid then have jaundice, since the blood type will be O, same as the mother’s?
    Really confused, and would like it if you cleared it up :)
    I’m glad to have stumbled across this.

  13. Rochelle says:

    My father has a B+ blood type and my mother is O+ and mine is A+. Is this possible?

    • 'Becca says:

      As I understand it, no. Talk with a doctor and make sure everyone’s blood type is identified correctly before you jump to any conclusions.

  14. EJ says:

    Both my parents are O positive and I just received notice from a blood donation that I am B positive. What?

    • 'Becca says:

      That is disturbing news. I think the first thing to do is make sure that your parents are correct about their blood types–it might be that they think they know but are mistaken, like my mom thought she knew that my brother and I were A+ without actually having had our blood typed.

  15. Peggy says:

    There are exceptions caused by mutations- Bombay phenotype or Para-Bombay phenotype is one of those…an AB- parent can have an O+ child under these circumstances..research mutation possibilities

  16. md.joy says:

    my blood group is o positive bt my sexual power is so high that i can’t maintain that’s why i am suffering a lot that can’t imagine.i am 21years old.i am not married.how can it possible to maintain my high sexual power?

    • 'Becca says:

      I’m not sure I really understand what your problem is, but it doesn’t sound like it has anything to do with your blood group. Perhaps you should see a urologist. I hope you will find the help you need.

  17. liz says:

    my father is ab positive and my mother is ab positive im o negative can I be there daughter

  18. Apu says:

    My and my wife both are AB positive. Now, my wife is 3 months pregnant. Will there be any problem for the same blood group.

  19. juderose says:

    MY father and mother is type A+. and i am type AB+. how can this be??

    • 'Becca says:

      I am NOT an expert on blood types. You should talk with a doctor and make sure all 3 of you know your correct blood type. There may be a mistake, because as I understand it, to be AB you need at least one parent with an A and one with a B.

  20. nadia says:

    am a+ and my husband is also a+ and we r expecting a baby,can this have a negative effect on the baby?

    • 'Becca says:

      No, as far as I am aware, there are no negative consequences of parents having the same blood type.

      However, it’s important to understand that your child will not necessarily have that same blood type. As I said in the article, both my parents are A+, but both of their children are O+. Do not assume you know your child’s (or anyone’s) blood type without having it tested. The test is easy and uses just a tiny amount of blood.

  21. juderose says:

    ok.. thank you.. :))

  22. Judy says:

    I am 0-, and 3 of my 4 kids do not have type 0 blood. None of them had any issue with jaundice.

    I guess we were just lucky?

    • 'Becca says:

      Yes, as I understand it the jaundice is not a certain thing. It’s just more common when the mother is O and baby is another type, than it is for newborns in general.

  23. klhaden says:

    both my parents are O+ and i am B+..is it possible????? even it is just 1%

    • 'Becca says:

      Let me repeat: I AM NOT AN EXPERT ON BLOOD TYPES. I have learned (from the commenter above, and then a little reading on the subject) that there are some genetic mutations that can cause an apparently impossible blood type. These mutations also mean that it can be dangerous for you to receive a blood transfusion, so PLEASE consult your doctor.

  24. amandah says:

    good luck friends my question is, is it possible 4 biological children 2 hv diferent blood groups?

    • 'Becca says:

      Yes. In fact, if one parent is Type A and one is Type B, it is possible for them to have 4 children with all different blood groups.

  25. rajesh says:

    is there any possibilities that parents blood group o positive and ab positive and the child group is ab positive

  26. hassea says:

    My blood group is O+ and genotype is AS and my wife is B+ and genotype is As what could our child blood group and genotype be

    • 'Becca says:

      I hadn’t heard of genotype AS. After looking it up, I did not find any really good information, but from what I understand this means both of you are carriers of a gene S for sickle cell anemia. When each parent has one copy of a gene, usually there is a 1 in 4 chance of their child getting two copies of the gene and therefore expressing the recessive trait, in this case having sickle cell anemia.

      I think you need to talk with a genetic counselor about the risk of sickle cell anemia and if there is anything you can do to prevent it. Good luck!

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  28. Jackie Saulmon Ramirez says:

    I had the Rh factor which means I had to get a RhoGAM shot after every delivery.

  29. Dez says:

    I didn’t know about this either. I had read about the Rh factor. Thank you for sharing this. My daughter just had a baby and the same situation. Mom is O+ and baby is B+, so they are treating her as well.

  30. Hilliary Tanner says:

    My mother was O-, my Father was A+ I am A-, Now both of my Kids are O-, that being said, a couple of questions… First, would that mean my husband would have to be type O or does it skip a generation and they inherited it from my mother. Is it normal to “produce” 2 O- children like that since the type is somewhat hard to find?

    • 'Becca says:

      Type O is not that unusual. All it takes is an O gene from each parent. If you have one O and one A, your blood is Type A because the A is dominant–same thing for B with O–but you can pass the O to your children. The links in the article explain more about this.

      Because your mom had two O genes, whether your dad had AA or AO, you got an A from him and an O from mom. Your kids then got your O along with an O from their dad. So his blood type is something that has an O–could be anything but AB.

      For the + and -, the + is dominant, so you must have two – genes and therefore that is all you can pass to your kids. if your husband has + blood but has one + and one – gene, each of your kids had a 50/50 chance of getting two -. If he also has – blood, then the two of you can have only – kids.

      Follow the links in the article for handy charts that better explain all this.

      • km says:

        My mom was o+ dad a- 3 out of 7 of is are o- my hubby is o-and so am I. But drs want to automatically hand out the rhogam shot as precaution. Oh well I refused ive only been with my husband & guess what my son is o negative. So those rules do not make that the only senerio. 3 of 7 of is are o negative with o and a parents

        • 'Becca says:

          I don’t see where any of your family is an exception to the rules. Two O- parents can only have an O- child (so you are right there was no need for you to take Rhogam). An O+ and A- can have O- children; the odds can be as high as 1 in 2.

  31. Jun says:

    I’m just curious but it possible for my blood type to be O if my dad is AB and my mom is B (based off what they say). Just wondering cause I donated blood and got the result of it as O+.

    • 'Becca says:

      A parent with AB blood cannot have a child with O blood unless there is a mutation. Make sure your parents are correct about their blood types. If they are, talk with your doctor. It’s important to know if you do have one of these mutations because it would affect your response to a blood transfusion if you ever need one.

  32. Ma. jenessa Marcojos says:

    If the father does not have the same blood like the mother..what would happen..there child Is it there child?is it needed that the both parents should have the same blood?

    • 'Becca says:

      The articles that I linked explain all the details. Any two blood types can combine. Having different blood types does not prevent two people from having children.

  33. naveen says:

    my doubt was a’m having o+ Blood and my wife also having o+ Blood it’s any problem for my child

  34. baby says:

    my husband having b+ and me o+ is it possibe my son has o- blood

    • 'Becca says:

      Yes. Look at the tables in the article I linked: An O parent and a B parent can have an O child. Two + parents can have a – child. So an O+ and a B+ can have an O-.

  35. Kavi says:

    my father and my mother’s blood group are B+ and A+ respectively and I am having O+. Is it possible?

    • 'Becca says:

      Yes, it is possible. If you read the articles I linked you will get the full explanation. The short version is that A and B are dominant, so a person with genes AO has Type A blood and a person with genes BO has Type B blood, but because each of them has one O gene they can have a child with genes OO who has Type O blood.

  36. Dan says:

    Hey. I have blood type O + and my wife type O- . What must we do before we have children and after birth?

    • 'Becca says:

      I don’t know of any concerns after birth. Your wife may need medication during pregnancy because of the Rh factor (- vs. +). Click the link of Rh factor in the article for more info.

  37. Rachel says:

    I wish the doctors would have told me about some if these things.. My son was born with B+ blood type n I have O+… My baby never got jaundice but I had the worst headache n my neck n back were locking up where I could barely move… The doctors n nurses never told me but this was caused by my son having a different blood type than me n I had a csection so when they cut his cord some of his blood must have mixed with mine.. It was very painful….

  38. Lexie says:

    Hi, I am wondering can a mother with type A+ blood and a father with O- blood produce a child with AB+ blood?

    • 'Becca says:

      No. The A mother needs a B father to produce an AB child.

      • Just a person says:

        It can be possible with the Bombay Phenotype. However, it is extremely rare.
        The father would have to have two hh mutations with the mother passing on an H revealing the fathers hidden B.
        To the best of my knowledge there is no test for the Bombay Phenotype. In the event of such a blood type outcome DNA testing would provide the only true answer.

  39. Darla Lane says:

    MY MOM HAS O+ AND MY DADDY HAD A+, HOW DID I GET A-DU+ {RH FACTOR}?

    • 'Becca says:

      I don’t understand your question–I don’t know what the DU means. I am not an expert in this at all. I hope you find a geneticist who can explain it.

    • Just a person says:

      The A- is from the A being dominant to the O and inheritance of one – from each parent (Each parent was a negative carrier +- ). You have the Duffy factor. Unfortunately I don’t know much about it. But here is some basic info that I found:

      Du Factor (Duffy Factor)

      The Du factor is related to the “Rh group” of blood factors. This is important because in some cases where the Rh group is missing (Rh-), the Du factor may be present. In these situations, the Du factor usually compensates for the lack of other Rh factors. This causes the blood stream to respond as if it where Rh+. When this situation occurs the person would be reported as Rh- Du+. These women are rarely at risk for Rh problems. Most often they are treated as if they are Rh+, unless they are getting a transfusion.

      So it makes you: Bloodtype A RH- DU+

  40. darwin hipol says:

    kinly help me,im a b+ and my wife is type o,what should be my son’s bloodtype?thank you

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  42. jane says:

    I would like to know if it is a problem if you are o+ and your husband is o+ will it affect the kids ?

    • 'Becca says:

      No, then your kids will all be Type O (but could be + or – because – is recessive) and it will be no problem.

    • mc says:

      Your child will be o positive. The rhogam shots are intended only for o/rh negative Mothers . Negative blood doesnt really hold protein like positive does your children will be fine.

      • 'Becca says:

        You are right that Jane will not need the Rhogam shot. However, it is possible that Jane’s child could be O- instead of O+, if both parents carry a recessive – gene. O- blood is fine to have; I just mention it so Jane will not assume she knows her child’s blood type without testing.

  43. My father was 0+ and my mother was AB RH -. I’m A+ and my husband was O+. Wh had an A- son. Is this possible?

    • 'Becca says:

      Yes, all of the above is possible. Baby gets one “letter” and one + or – from each parent, for the genes carried in baby’s cells. A and/or B dominates O, and + dominates -, in creating the blood type.

      Your father had to give you an O and could give you either + or -. Your mother could give you an A or a B and had to give you -. You must have gotten O and + from your father, A and – from your mother. The A and + are expressed in your blood type, while the O and – are hiding in your genes.

      You then pass one of your letters and either the + or the – to your child. Your husband, like your father, had to give an O and could give either + or -. Your son must have gotten A and – from you, O and – from your husband. The A is expressed in his blood type, and because he has two – and no + his blood is -.

  44. UNKNOWN says:

    I have read many of your articles. I have one question…if a person is B+ and both their parents are O+, is this possible??Could the person with B+ have the bombay blood group??

    • 'Becca says:

      I am not sure about the Bombay blood group. I really don’t know much about it. Normally, two O parents cannot have a B child. Talk to your doctor. I’m not an expert!

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  46. Milla says:

    Hi, can a mother A+ and the father AB+ have a child with blood type A- ? Thank you

    • 'Becca says:

      Yes, because negative is caused by a recessive gene. If you have one positive gene and one negative gene, your blood type is positive. If you have a child with someone who also has one positive and one negative, the child gets one gene from each parent, so it can get two negative genes and therefore have negative blood.

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