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.

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.

I hope this information is helpful to other families!  Knowing it earlier would have worked for me.  Visit Mom’s Library for more helpful information for parents.

248 thoughts on “Important Information on Blood Types of Parents and Children

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  2. 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!

  3. 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!

    • 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!

    • 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.

      • 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

        • 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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  5. 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.

    • 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.

      • 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!

  6. 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?

    • 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.

  7. 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.

    • 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.

  8. 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

  9. 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 can it possible to maintain my high sexual power?

    • 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.

      • I am B Negative and i am Rh negative but My husband Donated. Blood Two days ago and found out he is O positive and my 2 older kids are O Negative and my Baby is A what does that mean cause i didn’t mess around on my husband can u tell me something please

        • I’m sorry this confusion has come up in your family! I wish I had an easy answer for you, but I’m not an expert, and the best I can come up with is to have your blood and your baby’s tested again in case one of you was identified correctly, and then if you really are B and baby is A, talk to a doctor about the possibility of a mutation. Some blood type mutations are harmless while others can cause serious complications if you ever receive a transfusion. I hope you get good news!

    • 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.

    • 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.

  10. 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?

    • 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.

    • 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.

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

  12. 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

    • 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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  14. 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.

  15. 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?

    • 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.

      • 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

        • 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.

  16. 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+.

    • 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.

  17. 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?

    • 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.

    • 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-.

    • 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.

    • 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.

  18. 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….

      • 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.

    • 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+

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    • 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.

      • 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.

    • 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 -.

  20. 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??

    • 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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    • 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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    • Sickle cell anemia is genetic but not caused by the same genes that cause blood type, so your blood type does not tell whether you are sickle cell carriers. If there is a history of sickle cell in both your families, or if you are concerned because you belong to ethnic groups with high rates of sickle cell, you can get a blood test to see if you are carriers of the sickle cell gene; ask your doctor about “genetic counseling” to get a referral. It’s only if BOTH of you are carriers that you could have a child with sickle cell.

      I’m guessing from your spelling of fiancee (that spelling is female; “fiance” is male–but not everybody knows that) that she is female and you are male. In that case, your blood types are like Daniel’s (B+) and mine (O+) so your child would have a high risk of newborn jaundice. However, that is not a serious problem as long as you get treatment (see info in my article). If you’re the other way around (B+ mother and O+ father) then I am not aware of any complications that can result from your blood types.

    • Yes, both are possible. In order to have Type A, you need only one A gene; the other can be O. In order to have Type B, you need only one B gene; the other can be O. In order to have +, you need only one + gene; the other can be -. So, in this case the father’s genes must be a B and an O and at least one +, while the mother’s genes must be an A and an O and two -. Each parent passes one gene for A/B/O and one gene for +/- to the child. One child got B and + from father, O and – from mother, so has B+ blood. The other child got O and + from father, O and – from mother, so has O+ blood.

    • Their child could have ANY blood type! The only potential problem is if the child’s blood is positive, because the mother’s is negative, she will need to receive a Rhogam injection before the birth to prevent the baby from developing anemia.

  23. So, I am A+ and my husband is B+. What are the possibilities for our children? We had our first son in 2013 and are currently expecting #2 in July. Our son had jaundice at birth but not a serious form. If both parents are positive, will the kids be positive as well? Btw, my mom always told me I was 0+, it wasn’t until I gave blood for the first time in high school that I found out I’m A+. Hubby is military so we also know for a fact he’s B+.

    • Click through to the article for all the possibilities. There is an up to 25% chance of your having a – child, because + is a dominant trait, so if you have a + gene and a- gene you have + blood but can pass the – gene to your child; if your husband does the same, your child has two – genes and therefore – blood. But this will not cause any problems.

  24. I came across your article and felt like I had to write back. Thank you for sharing your story, it sounds identical to what had happened to me a both of my pregnancies…

    I really wish they did they had a book on abo incompatibility years back, but good to hear that more women are now educated about this.

    • Yes, although it’s in the Dr. Sears book now, it still wasn’t mentioned in any of my prenatal care the second time around, either. I feel that’s almost negligent–why not make it routine to hand Type O mothers a pamphlet about jaundice??

  25. I am O+, my husband is A+. All of my children are A+ except one. He is AB-. From everything that I have read, that is impossible. I have no doubt who the father is because I have only been with one man. Should I assume that someone was typed incorrectly?

    • That will be a normal, healthy child (unless there is something wrong that is not related to blood group). THERE IS NO REASON THAT PARENTS OF THE SAME BLOOD GROUP CANNOT HAVE A CHILD TOGETHER. This is clearly stated at the beginning of the article–did you read it? I have edited to make that fact appear in red text so it is more noticeable.

      I have seen in the comments on this article that many people of Indian ancestry are worried that having the same blood group is a problem. I am curious where you get this idea. I had never heard anyone worrying about it before I wrote this article.

    • No. Neither you nor your baby daddy have an A gene, so you can’t have a Type A baby. Talk with your doctor and make sure everyone’s blood type was identified correctly.

  26. is it possible for me to be related to my family? My mom is A+ dad same brothers same half sisters same grandmother mom side same grandma dads side same grandpa moms side is B and grandpa dads side unknown I am O+ from what a Harvard link told me there is only a 1% chance. other facts I have auburn hair bone white skin hazel eyes my mom is European colored my dad naturally tan moms hair is black dad red moms eyes brown dads blue green my brothers black hair brown eyes my 1 half sister red hair blue eyes my other black hair brown eyes my grandpa black hair blue eyes my grandma black hair brown eyes my other set of grandparents brown eyes and red and brown hair. I swear I am the whitest family member. my cousins have red hair blue eyes my aunt blond with blue eyes her husband red hair green eyes. i am seriously the black sheep in terms of features and blood type.

    • I’d like to see that Harvard link, because your blood type does not sound implausible to me at all. As I said in the article, both my parents are A+, yet both their children are O+. Many people with Type A have only one A gene and one O gene; many people with Type B have only one B gene and one O gene; when any two of these people have a child together, there is a 25% chance of the child getting two O genes and therefore having Type O blood.

      Hair, eye, and skin colors are more complicated genetically. From what I’ve seen in families, you don’t sound implausible at all; it’s just that your very light skin is at the extreme end of your family’s range of normal. Red hair is particularly quirky genetically. Since you have one parent with black hair and one with red hair, your having auburn hair (in between) makes sense, and the same for hazel eyes (in between brown and green).

  27. I had a quick question. So I have O+ (I’ve been tested and donated blood so I’m sure) and my parents have done the same. But my mom is A+, and my dad is AB-. How is it possible for me to have O+? I thought it was cool, but it’s kinda strange.

    • Talk to your doctor. The only way for an AB parent to have an O child is some type of mutation; if you (and/or your father) have one, that could be important to know.

  28. first i thank you for your wisdom and understanding to share with the world your knowledge. so i have a blood group of O positive so what is my genotype and the normal genotype and blood group for my choosen a pertiner. just to avoid skillcell or sick kid. thanks.

    • Your genotype for antigens must be OO because only people with two O genes have Type O blood.

      I can’t tell you your genotype for Rh factor. It could be +- or ++.

      Sickle cell anemia is genetic, but the genes involved are different from the ones that determine blood type. Talk to your doctor about getting your blood tested to see if you carry the sickle cell gene. If you do, you want to choose a partner who is not a carrier, adopt children, or brace yourself for a 1 in 4 risk of your child having sickle cell. But if you are NOT a carrier, your child cannot have sickle cell regardless of your partner.

      My guess is that you are the potential father? If so, you do not need to worry about jaundice caused by blood type incompatibility because Type O fathers do not cause this problem.

      Because you have + blood, if you have a partner with – blood, you could have a child with a serious iron deficiency at birth. However, this is easily treated before birth by giving the mother a Rhogam shot, so it’s not a reason to reject a woman with – blood.

      Please click all the red links in the article for more information.

    • Please read the article! It answers your questions! Especially, please click the link “Here is a typical article about Rh factor.” The only issue for you is that your wife may need the Rhogam shot.

    • PLEASE READ THE ARTICLE. There is no combination of blood types that reduces the odds of having a child. The only likely complication from your blood types is that you may need a Rhogam shot.

  29. we were having dicussion on blood group and we were saying that blood group of the same cannot marry,does why i was asking that question and because of that i have loose my wife when she noticed that i am a b positive and she was also a b positve

    • I am very sorry that your wife believed this stupid rumor rather than learning the truth. It’s already in the article, which I hope you read, but I will repeat:


      Please, every time you hear anyone saying that people of the same blood group cannot marry, please speak up and tell them it is NOT a problem.

    • Could you tell me WHY you and your friends were saying that people of the same blood group cannot marry? What is it that you thought would be wrong about it?

  30. Hi My brother had a girlfriend that he dated for 2 months and she fell pregnant. upon a visit to the doctor she was already 3 months pregnant, but they only dated for 2 month at the time. Upon the arrival of the baby a paternity test was done and the test confirmed that it was his baby. Months later we notice that my brother and the girlfriend belong to the same blood groups.
    can you please explain if there is any possibility that the baby might not be his because the father and mother belongs to the same blood group.

    • A paternity test compares the father’s DNA to the baby’s DNA. DNA testing is very close to 100% reliable. DNA is unique to each individual person (except that identical twins have the same DNA).

      Blood groups are NOT a good way to determine paternity because there are only 8 different blood groups among all human beings. If a baby’s mother had more than one partner in the month she got pregnant, it is really pretty likely that both partners have blood groups that could have combined with the mother’s blood group to produce the baby’s blood group. Click on “look at these handy tables” in the article and you’ll see all the options for combinations.

      The fact that your brother and the girlfriend are in the same blood group is MEANINGLESS here. What is suspicious is that her pregnancy began before he began “dating” her. If he had sex with her a month before they started dating, that explains it! Otherwise, either the doctor was wrong about the timing of the pregnancy or somebody lied about the paternity test.

      Repeating the paternity test is the best way to be certain.

  31. I realize this is a stupid question however I have O- and my wife has B+ and all 3 of are children match my wife’s blood typeB+, why is that?

    • B and + are dominant genes. That means that if a child gets a B from one parent and an O from the other parent, the child has B blood; + from one parent and – from the other, the child has + blood. Your genes are still there in your children and could combine with recessive genes in your children-in-law to make grandchildren with your blood type. Click the links in the article for more information.

  32. My mother, father and brother are A+, and I just found out I’m O+…
    Would that mean both parents have the AO genotype or can just
    one have that to have a child that O+ ?

      • Thank you so much Becca,
        My parents think the lab is wrong until I showed them the Bloodtype tables…I have one more unusual question.. In the 60’s, 70’s and 80’s my dad test O+, it was on his military dog tags, in1999 when he went in for surgery they said he is A+… He argued with the doctor and they tested again and it was A+ again.. He’s still confused and so was the doctor.. Any reason that can happen? He has never has transplants or any surgery prior to that.

  33. If mother is A+ and father is B+ ,first pregnancy – baby girl , but doubt on second pregnancy ,Is anything problem with second pregnancy

  34. 35 Male nd her blood group are o+ nd her femal kid blood group are also o+then what should be hapend in next …any complication about pregnancy

  35. Sir/mam my and my husband blood group is O positive and my chid blood group is B positive is this correct because I have read the article that if both parent have O poditive then child must be O positive plz reply

    • It would also be possible for your child to be O negative, but it is true that you cannot have a B child unless there is a mutation. Talk to your doctor about Bombay Phenotype or other possible causes.

  36. Hi, I am B+ and my hubby is 0 am due to have a baby in March 2015. What does that mean for our baby? cos this is our first baby, is our baby at risk of having sickle cell? And what those that mean for our genotype?

    • Please click on the link in the article for an explanation of your child’s possible blood types. I am not aware of any health problems that result from your combination of types. Sickle cell is genetic but comes from different genes than the ones that determine blood type. Ask your doctor about blood testing to see if you carry the sickle cell gene.

  37. Is it possible for my baby to have AB+ blood type and me to have B+ and my boyfriend to have O+ ? AB runs on my dads side of the family.

    • It is only possible if your boyfriend is not the father of the baby. AB comes from one parent having an A and one parent having a B in their blood type (look at the charts I linked to) so if you are sure your boyfriend is the father, most likely someone’s blood type was reported incorrectly.

  38. Hi. I am 33 years old and of O+ blood group and may husband is O-.
    In March 2014 I devastatingly had a still birth with our first child.
    We have been trying ever since for myself to conceive, however I seem to be struggling to fall pregnant.

    Can it be that me being a + is fighting his – and therefore resisting me getting pregnant?
    I have heard that + and – rhesus factors are not such a problem with the first birth, but I did not receive any treatment after the birth.
    Could this be the reason we are finding it difficult?

    Thanks in advance.

    • I am so sorry you had a stillbirth! I don’t think your combination of blood types is a problem or that any combination of blood types causes difficulty conceiving, but I AM NOT A DOCTOR, so it’s best to ask your doctor about this.

      Rh factor is a problem when the MOTHER is – and the FATHER is +. Since you and your husband are the other way around, that would not be the problem.

      I hope that you will soon have a healthy baby!

  39. i have o+ and my husband has ab+ . what all complications are there in my pregnancy and in new baby.. apart from jaundice any serious problem ??

    • I have no idea. As I’ve said, I am not an expert. Please consult your doctor. If you learn anything that might be helpful to others in this type of apparently impossible situation, please let me know!

    • It should not be possible for two negative parents to have a positive child. But I’m not an expert, so please talk to your doctor! The most likely explanation is that somebody’s blood type was identified incorrectly.

  40. Mam please tell me my blood group is O+ and my hasband ‘s blood group is O+ but my baby ‘s blood group is O- How is this posible

    • Please read the links in the article! Positive blood comes from a dominant gene, so you need only one + to have + blood. You and your husband could each have one – gene, and if this is the gene each of you passes to a child, the child has two – genes and no +, therefore has – blood.

  41. if the mother has blood type rh.negative and the father has 0.positive and has had the rogram shot after the first and second child . can one child be A.positive

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    • Do you mean sickle cell? Although that is a disease that affects blood and is inherited, it is not connected to blood type or Rh factor. It is caused by a recessive gene, so if both parents are carriers of the gene their child may have sickle cell. Ask your doctor about the blood test for this gene.

  43. Interesting article. Thank you for your research! I’m terrible at remembering any of our blood types, so will be asking at the next doctor appointment. I think I’m A+ and all the children are too, but I could be wrong. My husband is B+, I think. He said one of his parents is O… I’ll have to write everything down. I’d never really put much thought into the blood types before. (I’ve never heard anything like people of the same type not being compatible… must be an old wives tale. What did they do before blood typing?! 😉 ) I knew that there was something about having an Rh factor that was a problem, but that was as far as I had researched. I’ll have to look into getting Dr. Sears’ book. Thanks again for your article!

    • Father has a B gene and an O gene. B is dominant, so father’s blood type is B.
      Mother has an A gene and an O gene. A is dominant, so mother’s blood type is A.
      Child has an O gene from father and an O gene from mother. O is recessive. With no A or B present, child’s blood type is O.

    • O+ parents can have only O+ or possibly O- children. Your A+ brothers most likely are half-brothers who share only one parent with you, or they are adopted–or somebody’s blood type was identified incorrectly. I wish you the best in sorting it out!

  44. I injected sperm now I’m pregnant is it possible for doctors to predict or be sure thats it’s not my husband baby because i have to hide it from everyone i don’t want anyone to know pls help out. My husband is A+ I’m O+

    • I’m not sure I understand your situation, but I’ll try to explain the available information.

      Do you know the blood type of the sperm donor? If it is B or AB, there is a 50% chance that your child will have B blood, so blood type alone would identify that it is not your husband’s child, but if the sperm donor is A or O then the child’s blood type will not be a clue. (Whether the sperm donor is + or -, your child can have + blood because of getting a + gene from you.)

      It is possible for doctors to determine who is the father of your child, but that doesn’t mean that routine testing will reveal this information. I don’t know what is routine in other countries, but in the United States a baby’s blood type is not usually tested at birth. Even if baby’s blood type is tested, only certain combinations of baby, mother, and father blood types are impossible, so this might not reveal that your husband is not the father. Only DNA testing reliably establishes paternity, and DNA testing of your baby will not be done without your consent or a court order–even if the law is different in your country, because of the expense of DNA testing it is not something your doctor would do without telling you.

    • Yes. You must have one A gene (dominant, controls your blood type) and one O gene. Your child has a B from the father and an O from you, resulting in B blood type. Your child also has a + from you, resulting in + blood type regardless of whether father is + or -.

  45. I’m o positive and so is my husband and first son. My second son is a b…..I’m confused someone please explain this to me.

  46. is it possible to have mother and child being B rh positive and sickling negative whiles the father is sickle cell (SC)

    • I don’t know much about sickle cell anemia, but I do know that it occurs only in people who have two copies of the gene = one from each parent. So if the mother is not a sickle cell carrier, the child cannot have sickle cell anemia, regardless of the father…BUT the child could still be a carrier of one copy of the gene (from father) so if the child grows up and finds a partner who is also a sickle cell carrier, they could have a child with sickle cell anemia.

      Seek genetic counseling for more information. Any obstetrician, gynecologist, or midwife can refer you to a genetic counselor who can test to see if you are a carrier.

  47. My sister has A positive blood and after giving blood she said they have called several times wanting her to give blood for platelets . Why is this and what are the chances of being sisters we have the same blood type. What is so special about this type.?

    • I am not an expert! The only reason I know of for A blood to be in high demand is if it is the most common type in your area.

      The odds of your having the same blood type could be anywhere between 25% and 100% depending on your parents’ genotypes.

  48. My husband and I are both O+be but my daughter, our first child is B+be. . Please help me here.. she was so sick till the age of five …now she is eight and quite healthy.. her side effects after her long sickness is stuttering problem.

    • Did you mean “first born”? Blood type has NOTHING to do with birth order. It is determined by the egg and sperm that create that individual baby.

      It is possible for a B father and O mother to have an O baby. Because B is a dominant gene, a person with one B gene and one O gene has Type B blood. A person with Type O blood has to have two O genes because O is recessive. If those two people have children together, each child gets one gene from each parent, so the child can have B+O=B blood or O+O=O blood. Click the link “look at these handy tables” in the article for more information.

  49. I’m so happy to know this. I’ve had 3 children all born with jaundice they have the same blood type (A-) like their dad. But now I’m in a new relationship and I’ve been worried and trying to find out if this baby will have jaundice as well because his dad is A+ and I’m O+. So now I know since I have O antigen that any of my kids will more than likely have jaundice. This is great because I can let the nurses know before the baby is born that we need to look for the signs. Thank you so much for clearing this up for me.

    • No. If your blood type has been identified as AB and your parents are both B, talk with your doctor. There may be a mutation that could cause this, but if so it might affect your response to a blood transfusion if you ever need one, so it would be good to know. The other possibilities are that one of your parents is wrong about his/her blood type, or that one of your parents is not actually your biological parent.

  50. Please, I want to know if a Mother that is O+ and a Father that is A+ give birth to a child that is AB+ ? Thanks, and hope to hear from you soon.

  51. I am 0+ and my wife is A+ , I wanted to know whether it is a good match. We have no problem, all is going fine. Did I really make a good choice? I don’t want to get another partner but just to know whether it’s a good match.

    • Our child is type A- and is said to be a vegitarian whilst her mom is A+ and has to eat white meat or sea food, on the other hand I’m 0+ and i must eat beef and buffalo. Will there be no effects to our children?

      • If you read the article, you know that there will be no effects to your children from your combination of blood types. Even if you have more children, there is no possibility of their having a blood type that would be incompatible with their mother’s and cause health problems.

        About diet, are you talking about the book “Eat Right 4 Your Type”? I haven’t read it, but I have read that it is based on very unscientific reasoning. Speaking from my own experience, I am O+ and it’s absolutely untrue that I “must” eat beef and buffalo–for 15 years now, I have eaten meat of any kind less than once a day, beef only a few times a year, buffalo less than once a year, and I feel BETTER on this diet than I did when I ate more meat.

        It might be that different members of your family thrive on more or less of different meats, but this is not determined simply by blood type, if blood type has anything to do with it at all. Experiment to find the diet that keeps each of you feeling well.

    • Blood type has nothing to do with personality. You already know the answer to your question: You have no problems; all is going fine; you made a good choice!

  52. Blood group of my child and we husband & wife are same. Which type of problems can occur in future. Please give help & guide.

    • PLEASE READ THE ARTICLE!!! Your question is answered by the big red letters in the highlighted box! If the mother’s and father’s blood types are the same, this does NOT harm the baby.

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    • No, it is not possible for two O parents to have a child of any type but O. Have everyone’s blood type tested again in case there was a mistake.

    • This should not be possible because neither parent had an A gene. Read the article for details. Have everyone’s blood type re-tested and confirmed before you jump to any conclusions!

  54. if a mother is B+ as her blood group and she is AS and the father is A as his blood group and the Baby takes the mother blood group B+, thus it mean that the baby will be As automatically.

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