Blood Types 102: The Role of A, B, O, and AB Groups In Determining Paternity

Hello Doc, Is there any way of determining the father of a child before it is born?
Jamaica

Bllod Types 102

Dr. Greene’s Answer:

Having a baby is a lifelong responsibility and hopefully an even greater reward — for somebody! As a mother’s belly swells, she knows with deep certainty that the child is hers. Each time the baby moves or kicks, the bond between her and her child grows.

Depending on the situation, the father may be pretty sure that the child is his. For most of history, though, dads have had to rely on circumstantial evidence as the foundation on which to build this crucial relationship. After the baby was born, he could feel more sure he was the dad if the baby looked like him (“He has your feet, Honey!”), but often these early resemblances are at least partially creative imaginations.

In 1901 biologist Karl Landsteiner distinguished between three types of blood — groups A, B, and O. A fourth group — AB — was discovered a year later by another research team. As the inheritance patterns of these blood groups were worked out over the next decades, it became possible to include the use of blood type in determining paternity by excluding some men from being the fathers of some children. For instance, if the parents both have blood type O, then the children must all have blood type O. If a child were to have blood type A, B, or AB, then the presumed father must not be the real father. If the child’s blood type were O, then the presumed father might be the real father — but so might millions of other men.

Using Blood Type in Determining Paternity:Possible and Impossible Situations

Parents’ Blood Types

Possible Children

Impossible Children

A & A

A, O

B, AB

A & B

A, B, AB, O

none

A & AB

A, B, AB

O

A & O

A, O

B, AB

B & B

B, O

A, AB

B & AB

A, B, AB

O

B & O

B, O

A, AB

AB &AB

A, B, AB

O

AB & O

A, B

AB, O

O & O

O

A, B, AB

 

These are general rules, though, and exceptions apply. Very rarely, gene mutations may change the rules such that “impossible children” become possible. The geneticists at Stanford wrote a great explanation to this on the website for The Tech Museum of Innovation.

Today there are over 600 blood types known (as well as other tissue types called HLA types), which can make paternity testing far more accurate — but still not perfect.

Determining Father Before a Baby is Born

It is also now possible to determine the father before a baby is born. This is done by comparing DNA molecules — our genetic blueprints. To do this you need a blood sample from both the mother and the potential father (testing without the mother’s blood is possible, but more difficult — and more expensive). You also need a small sample of amniotic fluid (the water that the baby is floating in). Less than 1/4 teaspoon is sufficient for the test. The amniotic fluid may be obtained by a process called amniocentesis. This procedure is performed no earlier than 13 weeks into the pregnancy.

A court order or informed consent of all adults involved is required to proceed with paternity testing.

You will need to wait 3 to 4 long weeks for the results. Waiting for these test results can be a very anxious time. Rush orders take 10 to 15 business days, but cost about $500 extra.

Either way, if the test says that a man is not the father, then legally and truly he is not (it can absolutely exclude some men as the father of a certain child). If the test says that he is the father, then he probably is — there is about a 99.8% chance that he is. DNA testing is now legally accepted as able to determine paternity.

There are about one million two hundred eighteen thousand five hundred males in Jamaica (as of 1992). A positive DNA paternity test could limit the potential fathers to only about 2,437 of them (plus 0.2% of the tourists). Only 2 out of 1000 men could possibly be the father. As you can see, a positive paternity test is good evidence, but not an ironclad guarantee.

Paternity Testing

Prenatal paternity testing can be arranged through a company called Genelex, located in Seattle, Washington. They are very helpful, and can be reached at 1.800.523.6487 or healthanddna.com. The test costs $700.

If you wait until after the baby is born, DNA testing can be arranged through most local blood banks (many of which use Genelex). The blood sample can be obtained at birth. Otherwise, the baby should be at least 2 months old, since a fair amount of blood is needed for the test. In my area, this option costs about $600.

I realize that the circumstances that prompt a person to undergo paternity testing are often difficult. I hope that whatever you want turns out to be true. Even more, I hope that whatever turns out to be true becomes something that you learn to want.

Dr. Alan Greene

Dr. Greene is the founder of DrGreene.com (cited by the AMA as “the pioneer physician Web site”), a practicing pediatrician, father of four, & author of Raising Baby Green & Feeding Baby Green. He appears frequently in the media including such venues as the The New York Times, the TODAY Show, Good Morning America, & the Dr. Oz Show.

  1. Angela Jamerson

    Hi, my blood type is O+ and my boyfriend is O-. Our child is also O-. What is the chance the baby is his?

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    • There is a 25% chance that a child of an O+ mother and and an O- father will have an O- child.

      If you’re concerned about the paternity of your child, DNA testing is the best course of action.

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  2. Rishabh Bhardwaj

    Hi, it’s Rishabh.

    My blood group is AB+ and my wife blood group is B-. Because of opposite Rh factor we suffered from two abortion. Now what kind of precautions we have to take because we never want to suffered from above?

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  3. Sara

    hi i am b+ and my husband is ab- my first baby blood type is b+ i had a misscarriage in my second pregnancy .. Is there any problem in our blood types.. Most importantly i want to note that i didnt take any injection after my first prevnancy .. And am planning to have a second baby now ..is there anything i need to do?

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  4. Marie

    How do I find out my sons father ? Do I have to get both bloods from two dads then compare the blood types to is?

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    • The only reliable way to determine paternity is with a DNA test. If you are considering two possible fathers, you can test one and if he is positive, you do not need to test the other. If he is negative, the other potential father might want a DNA test to absolutely rule out a third candidate.

      Blood type tests are not definitive in determining paternity.

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  5. Caroline hunter

    Hi my husband is trying to go through a DNa test with whom he has been told is his father. But the man is making things difficult.
    We know he is rhesus negative blood type.
    My husband has just found out he is also rhesus negative.
    Is this anything to go by??? Please help.

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    • Blood groups can offer general information, but not specific information. Blood groups can say in general it is possible for this person to be a parent if certain information lines up. It can not say this person is the parent. Only DNA testing can provide that level of information.

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  6. Pauline

    I am a female & have two older male siblings.
    Both parents deceased.
    I am blood group : A POSS
    Eldest brother : A RHESUS D POSS
    Middle brother : O POSS
    Are we all full siblings?

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    • In this scenario, if one parent is A+ and one parent is O+, they could have children who are either A+ or O+. In other words, it is a possible combination.

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  7. summer

    My blood group is B positive and my wife blood group is O positive; Is it possible for us to give birth. On what percentage of change do we stand giving birth and our children’s blood group

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    • If one parent has B+ type blood and the other has O+ blood their children could have B or O, + or – blood types. The blood type can not be used to determine percentage chance of giving birth.

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  8. Nana Addo

    I highly impressed education on blood type

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  9. khushboo

    hello dr.
    my blood group is O positive and my husband having O negative blood group……can i conceive baby or not????

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    • Your blood group will not impact your ability to conceive. There are, however, many other factors that come into play when determining you ability to conceive.

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  10. gautam

    If a female has a blood group of “o+” and her husband of “a+”
    what is possibility of blood group of “b+” of twins born as boy and girI. Please answer give me very fast.

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    • If one parent is O+ and another is A+, their children will have either A or O type blood. There is a 6.25% chance each child could be Rh-. Before jumping to any conclusions, it’s very wise to have everyone’s blood type re-tested.

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      • gautam

        I am submitting a society problem which has now become anti social habits of disputes ultimately felt into legal case before court which is as below. A male married on 30 January 2001 and suffered with diabetes in 2005 year.as per family background, his father, grand father, cousin brother also suffered with diabetes and special kind of perkinsons disease also such man using medicine of ayurvedic , allopathic of diabetes with insulin injections as 2 when needed. His blood group “a+”.his wife moving blood group of ” o + “. During pregnancy, she used ayurvedic medicines for ensuring birth of boy as desired by her husband. After seven and half months of pregnancy, twins (one girl and a boy) born having blood group of ” b+”.suddenly, husband created problem with allegations of paternity of twins on the ground of “b+”blood group with support of genetic books.one of book of genetic of your also by which husband claimed and challenged the paternity of twins to other.he also filed a legal case before court of law.
        I request to kindly guide about the blood group of ” b + ” of twins and reason of it.is any effect due to suffering of diabetes insuline injection used by male and ayurvedic medicines taken during pregnancy by female also on blood group of twins as “b+”.I also request of your support due to genetic researcher and expert of your goodselve in this matter that which arguments from the side of female about blood group of twins as ” b + ” may be made before the court to save life of twins and also to get rid of bad allegations of paternity in the matter before court of law so that legal case mill be decided in favour of female on the ground of paternity in good spirits and faith of both may be made again by saying relations of husband and wife with their twins. Male always uses energy tablets since marriage. It is also submitted following of your message received- “if one parents is “o+” and another is “a+, there children will have either ‘a’or ‘o’ type blood. There is a 6.25% chance each child could be Rh-
        request to simplify public language the meaning of a 6.25% chance each child could be Rh- so that it any supportive meaning received in favour of female which may be submitted before court of law.

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        • In this case, DNA should be used to determine if this man is the father or not. The tests are fairly easily accessible and reasonably priced in the US, Canada, and Europe. I don’t know about the rest of the world. Blood type alone can’t determine paternity for legal purposes.

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          • gautam

            Resp. Sir
            thank you very much for your reply dated 24th August 2015 .sir we do not agree to DNA test at this stage due to children are having age of 8 years and their elder sister is 14 years old who knows the merits and demerits or prons and cons of DNA. Hon’ble high court of Rajasthan ,Jaipur has given an verdict that children will have bear the results of DNA so DNA not allowed such test .I have asked about blood group of ” a + ” of male ,”o+”of female and twins are “b+”.kindly give me any helpful reply which may be quoted before court of law so answer must be supported legally and can be argued before court of law up to its satisfaction resultant.

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          • I am sorry for your situation, however, with regards to blood types and paternity, I will quote from Dr. Greene’s article above:

            “These are general rules, though, and exceptions apply. Very rarely, gene mutations may change the rules such that “impossible children” become possible. The geneticists at Stanford wrote a great explanation to this on the website for The Tech Museum of Innovation.

            Today there are over 600 blood types known (as well as other tissue types called HLA types), which can make paternity testing far more accurate — but still not perfect.”

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  11. Newton

    what are the chances of having healthier babies when blood groups are B+ and B?

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  12. Elvis

    Dr, I’m sort of convinced my fiancé is RH O- while I’m B+. What are the chances of us having healthy babies?

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  13. Christina

    If I am o- and my sons father is o- is it possible he’s not my sons father if he is also o-??? I have researched everywhere and I have not found and an answer! Please help!!!

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    • Jane

      If both parents are O the child has to be O.

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  14. Sakib

    Doctor…..my wife’s and my blood group is o positive….and we are bloood related person.is there any problem to have a baby??

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  15. sushil

    My bloodgroup is B positive, my wife bloodgroup is B positive. What is my child”s blood possibilities? Please, urgent.

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    • Two B+ parents can have children who are blood group B or O and be either + or -.

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  16. SP Asapu

    Hi, My blood group is A(+ve) and My Wife blood group is O(-ve). What will be the possible and impossible blood groups for our Children.

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    • There is a 75% chance that your child will have type A blood and 25% chance of type O. There is a 75% chance your child will be RH+ and 25% chance of RH-. Each child has the same odds.

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  17. Lisa trenda

    Hi I have B negative blood. One of my children have B negative and my other child has o positive. They have the same father what would be his blood type.

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  18. Ebenezer Ampaabeng

    Doctor, can a Mum with genotype AA and a Dad with genotype AS give birth to a child with genotype AC? Why?

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  19. Via

    Hello. My blood type is A+ and my husband is B+, what are our chances of conceiving? Are we compatible?

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  20. Mamta.n Shetty

    My blood grup o+ and my husband blood grup also o+
    so now i am 7munths pragnant so my baby had any problem

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  21. Glenda Sainz

    My blood type is 0-. My mother was 0-. what are the possiblilties of my fathers blood type?

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  22. rupesh kumar

    my blood group is o negative
    so what is blood group of my
    father and mother…

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    • YC

      Your father can either be A or B or O but never AB

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  23. Debbie Jaime

    Hello Dr. I need your help my Mother was blood type A+ father was an O+, two of my brothers are A+ and 2 sisters are A+ like mom. I am O+ but 1 brother is AB+ does this mean he is not my father’s son?

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    • YC

      Yes looks like it

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  24. tps

    Can a a positive female and b negative male get married. Will there be any problems during pregnancy

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    • tps

      Can a female with A+ blood group and male with B- get married. Will threr be any problem during pregency

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  25. jenny

    if mother is b- and father a- can child be o-

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  26. lu

    my mother is ab + and my father o + and I am o+ it is possible

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    • YC

      Not possible

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  27. Jessica Lee

    Hello, DrGreene. According to my mother blood type is AB(whether is positive or negative, I don’t know),My father blood type I also don’t know. (I think is o positive!). They don’t want to go for blood test.Mine and my brother is A positive.I am the eldest.I was borned in 1972 year. My btother is 2 years younger than me,he is ok. But i just want to know what is happened to me if my parents blood type is like this??

    I am so confuse about myself and very appreciate if you can answer my question. I am from Malaysia.

    Thank you so much.

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  28. Katie

    I am Rhesis A – my baby has been born o- can the father be b+? Need help

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  29. Gimo

    My wife has o negative our son turned out to be o negative,am o positive,,is it genuine?

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  30. Maggie

    Hi,

    My mother is 0-. Is it possible for her parents to be A+ and B+?

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  31. Aniket

    My blood group is O RH positive & my Fiancee has A negative…what is the possibilities of having baby…with this blood group..can we have only one baby…or more?

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  32. Lucy

    Can a mum who is a, dad is o make b type?

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    • From what we know of genetics at this time, the answer is no. However, tests are not always accurate. It’s not unheard of for one of the three tests to be incorrect.

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  33. Aref

    if both parents are blood group O plus , and my child is A plus, it’s possible ?

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    • Yes, it is possible for two O+ parents to have a child who is A+.

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      • YC

        NO.

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  34. Jo

    Mother is A+ father is B- and I am O+. What are the chances that my father is truly my father? I know my mother had other partners in the same time frame, I can’t get DNA, as my father is deceased. Thank you.

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    • Odds are an interesting thing in blood types. I can tell you that the odds of a mother with A+ and a father with B- having a child with type O blood are 6.25% and the odds the child will be Rh+ are 75%. But for every child the biggest question is “can this parental combination produce “X” blood type child?” In this situation the answer is, yes.

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      • Carly

        My blood type is A +, my baby’s father is B+. Our son is 0+. Since I have never slept with anyone else since I married his dad, I can tell you it is possible.

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  35. Janelle

    I’m O- for sure. My husband does not know his type. We have three children together. One is A+ and two are B+. Is it safe to say my husband is most likely AB+? I know he’s the father, no question of paternity, just scientific curiosity. Thanks.

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    • You are correct, he would be AB+ because that is the only blood type that could be the father of children with either A+ or B+ if the mother is O-.

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  36. meena

    hi, my blood group is B – and my husband is AB+ what precaution we have to take before pregnancy????

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  37. Shay

    Hello I’m O+ and my baby is B+ and her father is B+ is that a good way to be certain that he’s her Father?

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  38. vicky shaw

    sir,
    I am ab- negative and my wife is o+ positive blood group ,so our born baby have any problem?

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  39. Lynnrose

    My type O+ and my husband AB+ and I have sex only with my husband and my son is O+ and my daughter O+ so are you saying its impossible…

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    • Perhaps you and your husband should have your blood type tested again. It’s amazing how many people think they know their blood type and find out it’s different than what the believed it to be.

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  40. theresa

    hi, am A+ and slept with two men… one is O+ and the other is A+.
    My child came out to be O+, would like to know who have the highest possibility as her father and how many percent accuracy would that be?
    I understand our parents (child’s grandparents) blood type would also affect my child’s blood type – if so how could I determine without going for paternity test?

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    • If the mother is A+, here are the possible outcomes:

      – If the father is O+, the baby has a 75% chance of being type A and a 25% chance of being type O and a 93.75% chance of being Rh+ and 6.25% chance of being Rh-

      – If the father is A+, the baby has a 93.75% chance of being type A and a 6.25% chance of being type O and a 93.75% chance of being Rh+ and 6.25% chance of being Rh-

      In other words, it is not possible to know the father of the baby without a paternity test.

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  41. michelle

    Halo. If I, the mother has a bloodtipe o- and slept with 2 diffrent men the ones bloodtipe is o+ and the other is a+, which blood tipe would it possibly be, so that I would know which of the 2 is the father of my baby? So confused at this stage.

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    • We know you are O- (and I assume you are really sure of this):

        — If Dad is O+ the baby will be type O and can only be type O. 75% chance of being + and 25% chance of being -.

        — If Dad is A+ the baby has a 75% chance of being type A and a 25% chance of being type O and a 75% chance of being + and 25% chance of being -.

      What this means:

        — If the baby is type O, it could be either father.
        — If the baby is type A, the type A man is the father.
        — The Rh (+ / -) does not help rule out either man.

      If the baby has type O blood, DNA paternity testing can help you determine which man is the father.

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  42. Victoria

    My son is blood type o positive and my boyfriend is o negative. What are the chances that he is my son’s father?

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    • It is possible if your blood type is A+, B+, or O+

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  43. Samantha

    My mom is A positive and my dad is O positive. My sister is O positive too, however I am AB positive. Looking at multiple blood type chart it consistently indicates that an AB positive child is impossible. Is that true or is it possible under certain circumstances?

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  44. Anonymous

    Dear Doctor, my father’s blood type is AB and mine is O, is it possible that he is my father? I wonder if you can send me an e-mail to this answer?

    Regards!

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  45. Cindy

    The father is AB+ and the mother is O+ and they have a son who is O+. These parents are both white. The mother had no other sex partners. Are you saying it is impossible for them to have an 0+ child?

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    • Arenae

      I am O+. My dad is type AB and my mom is O. Research “Bombay” blood type or hh blood type. It will give you more explanation as to why this is.

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  46. Archie

    My mom is B+ ve and dad is AB. I’m O positive.. Is it possible?

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    • I’m assuming you’ve looked at the chart on this page? If so, your real question may be, “what do I do now?” There are several options. I recommend that you talk to your mom first and tell her your fears. If she is firm that your mom and your dad are your biological mother and father, then it’s pretty easy to get everyone retested to make sure the blood types are what you think they are.

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  47. David Nandwa

    My blood group is o positive and my wife is b negative. What precautions can we undertake to our unborn baby. She is 6 months pregnancy.

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  48. Emmanuel Yeboah Dunga

    if both parents are blood group O, then, under normal circumstances, all the children should have blood group O and no other group. But you can do the testing again if there is any doubt

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  49. Lori T.

    Hi my mom said she is AB- and my dad is B+. I’m O-. I know my mom has the RH negative factor, which I have as well. Is it possible my dad is my dad?

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  50. Susan Knight

    My parents are both A positve…I am B negative…is this possible?

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    • There is a small chance that two A+ parents could have a child who was Rh-, but two parents with type A blood can’t have a child with blood type B.

      Before you jump to conclusions, it’s wise to have all three of you tested again to confirm your blood types. It’s not unusual for people to think they are one type when they are another.

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  51. Reynaldo

    me and my wife are type O but my eldest son blood type is type AB. Is it Possible?

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    • Tina

      No, sorry to have to inform you, but its not possible. Maybe you all should be retested.

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  52. Namrata

    My Blood Group Is A+ and My Husband blood group is O- Please let us know which blood group or children will have? Also please let us know what are the precaution we have to take during the pregnancy? And is there any problem in making baby if blood group is A+ and O-

    Thanks & Regards,

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  53. Martin Luther

    My Blood Group Is B+ and My Wife is B- Please let us know which blood group or children will have? Also please let us know what are the precaution we have to take during the pregnancy?

    Thanks & Regards,
    Martin Luther

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  54. vinit

    My blood group is B positive & my wife has B negative…what is the possibilities of having baby…with blood group..can we have only one baby…or more???? Reply fast plzzz. It’s urgent! ***plzzz

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    • sakshi sagar gaikwad

      my blood group b negative & my husband blood group b positive whats complication pregancy please reply me fast

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  55. Nikhil

    My blood group is B positive and my wife blood group is O positive; Is it possible that my baby have blood group O negative.

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  56. Michelle

    Hi Dr, both my parents are O and I am A+. My mom had lots of blood transfusions before I was born. Is this possible?

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