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

The use of blood type in determining paternity is beneficial by excluding some men from being the fathers of some children. It is not a definitive test.

Question

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

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.

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.

About the Author
Photo of Dr. Alan Greene
Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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Recent Comments

Dear Sir,

i have some confusion, my blood type is B+, my husband is B, he is not sure + or -. but our son comes with blood AB. is impposible. i just getting to know. is anything wrong with the hospital?

look forward to hearing from you soon.

Thanking you

Hi Sarah,

I can understand your confusion. Likely one of the blood types is not what you think it is. It would be wise to have all three blood types retested.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hello .. i am so confused whats this impossible child mean.. My husband is AB and i am A+ .. And our baby is O .. is it possible ? .. All i can imagine is either she got my blood type or her dad .. I hope you answer me .. Thanks..

Hello Khisner,

When someone or a website says “impossible child” it means, if the parents have the stated blood types, they could not have a child with the blood type you’ve input. In your case, IF the father has type AB blood and the mother has type A blood, their child could not have type O blood. That combination of three blood types is impossible.

If the father has type AB blood, each of his children can have type A, B or AB, depending on the blood type of the mother.

IF the mother has type A blood, each of her children could be type O, A, B or AB depending on the blood type of the father.

You may ask why this is.

— Blood types are comprised of two alleles. The most common (by far) are A, B, and O.
— If a person has type A blood he or she has at least one A allele. He or she can have two A alleles (AA) but can also have one A and one O (AO). Both are called type A blood.
— If a person has type AB blood he or she has one A allele and one B allele.
— If a person has type O blood, both alleles are O.
— Each parent passes down exactly one allele to each of their children.

What this means for you is IF the father has type AB and the mother has type A, the father can only pass down an A or a B. He can not pass down an O allele, so it is impossible for his child to have type O blood (because that is two Os).

It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested before jumping to any conclusions.

I hope this makes sense, but if you have questions, please don’t hesitate to ask.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hello~

I consistently get frustrated by blood type charts and calculators because my sister and I are apparently impossible blood types. I want to know the infinitesimal percentage of our blood types.

My mother is O- my father was 0+ (there was never any affair or baby-switching at a hospital as I was born at home.)

I am B+ my sister is A+. I understand that mutations must have occurred for us to have the blood types we do, but what was the likelihood? I just want a number/percentage. ㅠㅠ

Hi Dannie,

As far as I know, there are no numbers for this situation. This must be frustrating. Ideally, you would get all your DNA tested and take the results to prove your two parents are both parents to you and your sister. Then take those results to a researcher studying rare blood type mutations. I don’t know who is doing that work. It would likely be at a major research hospital or university. Since you use the past tense when referring to your father, I wonder if this is still a possibility.

There is one scenario you haven’t considered — perhaps your parents weren’t able to conceive naturally and decided together to use a sperm donor. No affair. No switching at birth. No bio father waiting in the wings to find. Just loving parents helped along by science.

Sadly, you may never have the answer you’re looking for.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I am a bit disturbed. Been in a long marriage and have a four-year-old child. The child has a congenital defect. Father is A negative. Mother is A Positive. The child’s blood type is AB+. Is there even a minute possibility of this?

Dear From Asia,

Our current understanding of genetics is that it is not possible for one parent to have type A- blood, the other parent to have type A+ blood and their child to have type AB+ blood. If one parent is A- and the other is A+ they can only have children who are A+, A-, O+ or O-.

It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I still cannot get this genotype thing. I was told that blood type comes from the father even though other genes may come from the mother. My mother is type O, my father is type B, you’re saying that it’s normal for me to have type O?

Hi Wilfene,

It can be confusing, but here are the basics:

  • Blood types are comprised of two alleles.
  • The most common (by far) are A, B, and O.
  • Each person gets one from their mother and one from their father.
  • If a person has type B blood he or she has at least one B allele. He or she can have two B alleles (BB) but can also have one B and one O (BO). Both are called type B blood.
  • If a person has type O blood he or she can only have two O alleles, which means he or she received an O allele from the mother and one from the father.

What does this mean for you?

  • If your mother has type O blood, she would have to pass an O allele down to you.
  • If your father has type B blood, he could have past a B or an O allele down to you.
  • If you have type O blood, each of your parents past an O allele down to you.
  • This outcome is completely normal. In fact, 25% of children with an O and a B parent have type O blood.

Please let me know if you have any additional questions.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

hi
im b+ the mom is A+ and baby is O. that seems to be a 6% chance baby is mine. i am doing paternity test. what is your opinion on a 6 % chance

Hi Anthony,

Great question, but that’s not how it works.

If one parent has type A blood and the other has type B blood each of their children could have type A, B, O or AB blood. All these types are completely possible. That means if one parent has type A blood and the other has type B blood, BLOOD TYPE CAN BE USED TO SUGGEST PATERNITY.

It does mean, if one parent has type A blood and the other has type B blood, there is a 6.25% chance each of their children will have type O blood. This is still a common outcome.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hello! I have an odd question! My mother is O- and me and my sister are both O+. My mother is not sure if my older sister is my fathers daughter as well. It could be him or another guy, but we have no clue who the other guy is. What are the chances that me and my sister would have the same blood type with different fathers? Thank you so much!

Hi Katie,

Blood types can only provide limited information about parentage. They can exclude some possible combinations, but they can’t actually identify specific people in a family. That said, O+ is the most common blood type. 37.4% of people have this blood type. This means the chance of having different fathers is higher than if you had a rare blood type. Only .6% of people at type AB- blood, so if that was both you and your sister’s blood type, it would be much more likely you had the same father.

If you really want to get this information you can run DNA paternity test on your older sister and your father. A DNA paternity test is the only test considered definitive. They are fairly inexpensive, can be ordered online, taken in the privacy of your own home, mailed in, and results received by mail. They are considered 99.999% accurate.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi! Good Day.

I’m the mother O+ type my husband is B+.. is it possible that my daughter is A+? Please help me. Thank you so much.

Dear RC,

Our current understanding of genetics is that it is not possible for one parent to have O+ blood, the other parent to have B+ blood, and their child to be A+ blood. For a child to have type A blood, one of the parents would need to have AB or A blood type.

It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Myself and father are o+ two of our sons are A+. We know the blood types are correct due to us having blood transfusions. I have my DNA done and they sent me the raw data. Where would I look to see if maybe I’m AO

Hi Meme,

If you are AO, that would be called A. Type O means two O alleles. Type A is one A and one O (AO) or two As (AA).

Have you had the baby’s father DNA done? Perhaps he has type A blood?

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My mother is o+ . Confirmed by 4 different hospitals,labs and clinics.
I am AB+. Confirmed by 12 hospitals, labs , clinics, and Red Cross. We have done a maternal testing to make sure I wasn’t swapped as an infant. It’s confirmed, I’m hers.
Is this really that rare for so many doctors to tell me that it’s impossible ?

Hi Alicia,

This is extremely rare, but there is at least one instance I know about. There may be others. It is possible, one of your blood types doesn’t fit with the ABO system. That is the case with Bombay Blood type.

About 0.0004% or 4 per million people in the general population have what is known as the Bombay Blood type. In some places such as Mumbai (which was formerly called Bombay) the occurrences can be as high as 0.01% or 1 in 10,000. This group does not fall into the ABO system and the usual tests for ABO blood show them as group O.

The Bombay blood type is usually only found in small communities where there are other people with the hh blood type. Both parents have to be h carriers, though a parent can be a carrier without actually having Bombay type blood.

DNA paternity tests are still considered accurate (99.999%) with type hh blood and are considered the only accurate test for paternity.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am NOT Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My Mom was AB+. I know this to be a fact because she was a double amputee before her death and had many blood transfusions. My dad is O+. I know this to be a fact because he is currently in the hospital and received a blood transfusion just last night. I am O+ I know this to be a fact. My dad and I both did the Ancestry DNA test and he is my biological father. My mother was my mother because my half sister who was her daughter did the DNA test also and we are half sisters. Am I a freak of nature?

Hi Misty,

There is a very rare blood type (0.0004% or about 4 per million in the general population) known as the Bombay Blood type. In some places such as Mumbai (which was formerly called Bombay) the occurrences can be as high as 0.01% or 1 in 10,000. This group does not fall into the ABO system and the usual tests for ABO blood show them as group O.

The Bombay blood type is usually only found in small communities where there are other people with the hh blood type. Both parents have to be h carriers, though a parent can be a carrier without actually having Bombay type blood.

If you suspect you may have the Bombay blood type talk to your doctor about a specialized test for this blood type as it does not show up using the normal ABO blood type tests.

DNA paternity tests are still accurate (99.999%) with type hh blood and are considered the only accurate test for paternity.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi am B+ and my wife is A+ how comes my son is A-

Hi Neville,

Thanks for writing in.

It is completely normal for one parent to have B+ blood, the other to have A+ blood, and their child to have A- blood. Here’s how it works …

Blood types are comprised of two alleles. The most common (by far) are A, B, and O.
— If a person has type A blood he or she has at least one A allele. He or she can have two A alleles (AA) but can also have one A and one O (AO). Both are called type A blood.
— If a person has type B+ blood he or she has at least one B allele. He or she can have two B alleles (BB) but can also have one B and one O (BO). Both are called type B blood.

Rh+ means a person is positive for the D antigen. Rh- means a person does not have the D antigen. Two parents with Rh+ blood can have children with Rh+ or Rh- blood depending on if either of them pass on the D antigen or not.

Here’s how that could work out for you:
— If you have type B blood, it is comprised of one B allele and one O allele.
— If your wife has type A blood, it is comprised of two AA alleles or one A allele and one O allele.
— If your child has type A blood, he got an O allele from his father and an A allele from his mother and neither passed on the D antigen.

I hope that helps and please let me know if you’d like further explanation.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

If my moms blood type is A+ and my dads blood type is O. Is it possible to have a child that is AB.

Hi Kim,

Thanks for writing in.

If one parent has type A+ and the other has type O, their children can not have type AB blood.

In the above statement, “if” is key. It is wise to have all your blood retested. It’s not uncommon for blood types to be different than they are thought.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My son is one of the impossible. My husband is O+ and I’m B+ and my son is AB+. No there is no possibility of another father. I was thinking someone made a mistake on our blood type, but I got it checked by two sources. It’s crazy that they say this is impossible.

This is also my case, and of great importance to me. My mother is type A, my father type O, and I am AB+. Sandy, the writer above, said she got every one checked by 2 sources, so you suggested a DNA test for all 3 family members. I would love to know if they followed up on your advice and what the outcome was. You did mention that there are SOME exceptions to the “impossible child” rule, but didn’t go into detail. Can you elaborate, or at least confirm that if indeed mom is A, dad is O, and I am AB, then dad is not biologically dad, right?

Hi Sanday,

Thanks for writing in.

Have you done DNA testing on all three of you? I would think confirming you are the mother, father, and child with those blood types would be very interesting to researchers.

DNA tests are fairly inexpensive, can be ordered online, taken in the privacy of your own home, mailed in, and results received by mail. They are considered 99.999% accurate.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

mom AB+ AND RH –
dad O
= an A+ child ?

Hi Jon,

If one parent is AB+ and the other is O-, they can have a child that has A+ blood. In fact, they can have children with A+, A-, B+ or B- blood.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi, Two alleged fathers. One is blood type A and the other is blood type O. Mother is blood type O and child is blood type A… child really looks like none of them per say, however, shares similar forehead with the type O alleged father….. is it possible that the type O is the biological father?

Hi Caty,

Blood types are comprised of two alleles. When a person has a child, he or she passes one of the alleles down to the child. Each child gets one from his or her father and one from his or her mother.

Blood type names are a little confusing. We call the most common blood types A, B, and O.
— If a person has type A blood he or she has at least one A allele, but the other can be O.
— If a person has type O blood he or she has two O alleles.

That means a mom and a dad with type O blood can only have a child with type O because they each can only provide an O allele. If a child has type A blood, one of the parents must have type A or type AB blood.

TIn an issue of paternity, blood types are not considered definitive. If there is a question, a DNA paternity test is the only test considered definitive. They are fairly inexpensive, can be ordered online, taken in the privacy of your own home, mailed in, and results received by mail. They are considered 99.999% accurate.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Me and my husband are o+, but our child child is b+, Is it possible?

Hi Neha,

Our current understanding of genetics is that it is not possible for both parents to be O+ and a child their child to be B+. Two O+ parents can only have children with O+ or O- blood types.

It is wise to have all your blood retested. It’s not uncommon for blood types to be different than they are thought.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Is it possible For an O+ father to have a AB- child regardless of the mothers blood type?

Hi Kim,
If one parent has type AB blood, he or she can only have children who are type A, B or AB.
It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested as the next step.
I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Im just wondering how likely is my bio father my actual father. He is O- and my mother is A+ and i am AB+.

Hi Julia,

Thanks for writing in.

If you are AB+ one parent would be type A+, A-, AB+, or AB- and the other parent would be B+, B-, AB+, or AB-. But they could not both be Rh-, so if one parent was A- or AB- the other would have to be B+ or AB+. If you are AB+ neither biological parent can be O+ or O-.

It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested before jumping to any conclusions.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I have an A- blood type but nobody else in my family does. What blood types would my parents have to be for me to have A- blood type?

Hi Yanel,

Thanks for writing in.

If you have A- blood one of your parents would need to have A+, A-, AB+, or AB- blood type. The other parent could have A+, A- B+, B-, AB+, AB-, O+ or O- blood type.

If you’d like further explanation of how this works, let me know.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi Dr. Greene,

If I have blood type A+, my two daughters are both A+, does this mean my husband would either have: A+, B+, AB+ or O+ blood type? We are trying to find out what blood type my husband is as he does not know.

Thank you,
Brenda

Hi Brenda,

If one parent has A+ blood and the child has A+ blood, the other parent could be A+/-, B+/-, AB+/-, or O+/-. In other words, with the information you have you can not rule out any blood type. If you’d like an explanation, please let me know.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

If a child is RH-, would the father have B type blood?

Hi Michelle,

The Rh system of classification and the ABO system are different.

The Rh system looks for the presence or absence of the D antigen. The ABO system describes the type of alleles that make up the blood. What that means for you is blood type B is not related to Rh+ or Rh-.

It’s like asking, could a child who is 2’3″ tall have a father that weighs 200 pounds? Yes, he could, but the two are not related.

Or put another way, a child with Rh- blood could have a father with type B blood, or type O blood, or type A blood, or type AB blood.

Does that make sense?

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi! If a mother is B pos and the father is A pos can the baby be O neg

Hi Deb,

Thanks for writing in.

It is completely normal for one parent to be B+, the other to be A+ and their child to be O-. In fact there is a 6.25% that each of their children will be O-.

Please let me know if you’d like an explanation.

est, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hello

I am Rhesus o neg blood group what are my parents blood groups likely to be for me to get this blood group?

Hi Sarah,

If you are Rh-, your parents could be Rh+ or Rh-. If you are Rh+, at least one of your parents must be Rh+, but the other can be Rh+ or Rh-. Basically, being Rh-, doesn’t rule out any combination, but being Rh+ does rule out both parents being Rh-.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi Doc,
I have a child that recently had to have a blood transfusion. The mother told me her blood type is A and that she was not a match. The baby blood type is B.. so I went to go get my blood tested and I am O+.. What is the possibility of us having a child with a B type.. I need to know asap please respond,

Dear James,

I hear your concern. If one parent has type A blood and the other has type O, each of their children can have type A or O blood, but not type B. However if one parent has type AB and the other has type O, each of their children could have type A, B or O blood.

It’s not uncommon for blood types to be different than they are thought, so it is wise to have all three of you re-tested.

If there is still a question, a DNA paternity test is the only test considered definitive. They are fairly inexpensive, can be ordered online, taken in the privacy of your own home, mailed in, and results received by mail. They are considered 99.999% accurate.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

please can anyone explain my rarity. i came from a dominant A group both great grandparent were As, my grandmother A, grandfather O, My mother A, father O, I am an O my husband is an O but my daughter is an A which according to the square is impossible but he is the father, my GP told us as i was worry about un necessary accusations to parentage, he said there are what they call a rare child, where both parent are an O but either mother or father come from a very dominant mutation A group can produce an A child whilst both parents are o. why can’t they mention this on the web.

Hi, so apparently both my parents are O and I’m b+… My mom just told me who my “dad” is and him and I are both curious about this. Could this still be possible ??

Hi Ark,

Thanks for writing in.

It’s not considered possible for two parents with type O blood to have a child with type B blood. However, it is not uncommon for blood types to be different than they are thought. At this point it is wise to have all your blood retested. If they still come out the same, consider a DNA paternity test is the only test considered definitive. They are fairly inexpensive, can be ordered online and taken in the privacy of your own home. They are considered 99.999% accurate.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My father is A+ and My Mother is A- so how could All 3 Children have A- blood ?

Hi Barbara,

Thanks for writing in.

As I’m sure you’ve read, it is perfectly normal for one parent to be A+, the other to be A- and their child to be A-. In fact, there is a 93.75% chance each of their children will have type A blood and only a 6.25% chance each of their children will have type O blood. There is a 75% chance each child will have Rh+ blood and only 25% chance each child will have Rh- blood.

If I have read your question correctly, your concern is that all three children are Rh-, when statistically, only 1 in 4 children would be Rh-. In blood groups, the odds are calculated over a large population group. 25 children out of 100 would have Rh- blood, but that does not translate into 1 out of 4. Think about it this way, if you tossed a coin 100 times, statistically half the time it would land on heads and half the time it would land on tails. But that doesn’t mean every other time it would be tails. In fact the coin could land several times in a row on tails and laters, several times in a row on heads.

Does that answer your question? If not, let me know.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi i am B+ and my son is B-, what are the types of blood his father can be?
Thanks

Hi Tara,

Thanks for writing in.

If you have B+ blood and if your son has B- blood, his father could have B+, B-, O+, O-, A+, A-, AB+ or AB- blood. As you can see, with this combination of mother and child no types are eliminated for the father. If you’d like an explanation, please let me know.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

URGENT OPINION REQUEST PLEASE
Hello Doctor:

I am a VERY WORRY grandmother. My Son and his Girlfriend just had a Baby, She is O+ and my Son is A+ and the Baby turns out to be B+. How can this be? possible? on top of that the Baby is Albino. We are going to do a Saliva DNA Test next week, the Baby will be 1 month old.

Sandy

Dear Sandy,

Thanks for writing in.

It seems you’ve read the above article (and possibly many others) that state an O+ parent and a B+ parent can not have an A+ child. From everything we now know about genetics, that is true. But keep in mind, it is common for blood types to be different than they are thought. This can happen as a lab error, a reporting error, or someone remembering a different type than they were told.

A DNA test is the best way to move forward. They are extremely accurate and considered definitive in determining paternity.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

my blood type is B- am i going to have a baby ?

Being B- does not need to prevent someone from having a healthy baby, but it’s important for the people caring for you to know that you are Rh-

Is it possible for a O+(Father) and B+(Mother) have a B- child?

Hi James,

Thanks for writing in.

Yes, it is possible for an O+ parent and a B+ parent to have a B- child. In fact, there is a 75% chance their child will have type B blood and a 6.25% chance their child will be Rh-.

If you’d like an explanation, please let me know.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi! Good afternoon, is there a possibility that the child is O+ considering both his parents are A+?

Hi Susan,

Thanks for writing in.

Yes, it is possible for both parents to be O+ and their child to be A+. This is perfectly normal. If you’d like an explanation, please let me know.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My blood type is A+ and my ex husband’s blood type is B- and there have been questions about the paternity of one of our three kids. She is O but I can’t remember if she is +or-. Her sister is A- but I do not know her brother’s blood type. But there is no question of their paternity. Is it more likely that my ex husband is not her father? Thanks

Hi Melissa,

If one parent is A+ and the other is B-, they can have children who are O+ or O-. They can also have children who are A+, A-, B+, B-, AB+ or AB-. As you can see, with this parent combination, no blood type is impossible.

If there is a question about paternity, a is the only test considered definitive. They are fairly inexpensive, can be ordered online, taken in the privacy of your own home, mailed in, and results received by mail. They are considered 99.999% accurate.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not
Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi Dr father’s blood group ab+ and mother’s b+ and child’s B- is it possible

Hi Johnson,

Thanks for writing in.

Yes, if one parent is AB+ and the other is B+, they can have a child with B- blood.

It is possible for two parents with Rh+ blood to have a child with Rh+ or Rh- blood.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I am AB positive and my husband is O negative. Our daughter is B negative. Is that considered correct?

Hi Kim,

Thanks for writing in.

If one parent is AB+ and the other is O-, they can have a child who is B-. They can also have children who are B+, A+ or A-.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My Brother And His Wife Both Are” O” Positive But The New Born Child Has Got “A “Positive As His Blood Group. Is That Possible

The mother is o- & father is o+ & the child is born A+, is it possible??

My Bd group is B+ve , My Wife bd group is O +ve , which bd group possible in baby .

Hello Jsr,

If one parent is B+ and the other parent is O+, each of their children can be O+, O-, B+ or B-.

I hope that’s helpful.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

If the father is B+ve and mother is O+ve, can the child be B-ve?

Suhail Ahmad (Pakistan)

Hello Suhali,

Thanks for writing in.

If one parent is B+ and the other parent is O+, they can have a child who is B-. This is very normal.

Please let me know if you’d like an explanation.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi, my father is O RH+ and my mother is B RH+ what are the chances of me being O RH- ??
From Dean

Hi Dean,

Thanks for writing in.

If one parent has type O+ blood and the other has type B+, each of their children have a 75% chance of having type B blood, a 25% chance of having type O blood, a 93.75% chance of being Rh+ and a 6.25% chance of being Rh-. This means each child would be more likely to be B+, B- or O+ than being O-, but all four possibilities are perfectly normal.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi
My father’s blood group is O+
My mither’s blood group is also O+
Bt my blood group is B+ how is it possible
Plzzz reply imidately

Neha,
Me and My husband are O+ and our son is B+ You are not alone. The chart above is “impossible child “is so wrong. I also researched on that.

Neha,

Thanks for writing in.

Our current understanding of genetics is that it is not possible for both parents to be O+, and their child to be B+. Two O+ parents can only have children who are O+ or O-.

However, it’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood re-tested before further inquiry.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Please help, I am O+ my boyfriend is AB- is it possible me to carry our child to full term and for us to have healthy children together ? We have had a couple of early miscarriages and am wondering if our blood is compatible and what we can do to aid in having a healthy baby together. Thank you

Jay Jay,

I’m so sorry for your loss.

Blood type incompatibility is only an issue if the mother is Rh- and the father is Rh+. Dr. Greene writes about it here.

Wishing you all the best as you continue to try to have children.

Sincerely, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

My dad is A- and my mum is A+, what are the possible blood types their children (me and my sisters) could be.

Hi Mackenzie,

Thanks for writing in.

If one parent is A- and the other is A+, each of their children could be A+, A-, O+ or O-.

Let me know if you’d like and explanation.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hello doctor my blood group is AB+ & my wife O – now what is the possibility in our child?

Hi Ayan,

Thank you for writing in.

If your blood type is AB+ and your child’s mother’s blood group is O-, your child could have A+, A-, B+ or B- blood.

I hope that’s helpful.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

will Father’s A- and Mother’s B+ affects baby’s health??

Hi Monika,

Thanks for writing in.

Sometimes there is an issue with blood type incompatibility, but it’s only if the mother is Rh- and the father is Rh+. You can read Dr. Greene’s explanation here.

I hope that’s helpful.
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Will o positive and o negative harm the baby I am just now about to ovulate. I am o positive my husband to be is o negative.

Hi Donalyn,

Thanks for writing in.

You may have heard of blood type incompatibility. That is only an issue if the mother has Rh- blood and the father has positive blood. You can ready about that in Dr. Greene’s article How To Determine and Manage Rh Incompatibility.

I hope that is helpful.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

I am O- mother and my husband is a B+ father. What blood types will our children be?

Hi Wanda,

Thanks for writing in.

If the mother is O- and the father is B+ their children can be O+, O-, B+, or B-.

Has your doctor talked to you yet about Rh incompatibility? This is of concern when the mother is Rh- and the father is Rh+. Dr. Greene writes about it here.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

Hi sir my blood group is o positive and my wife group is b negative but my baby group is b positive is this possible?

Ali,

Thanks for writing in.

Yes, if you are O+ and your baby’s mother is B-, it is possible for your baby to be B+. This is an expected outcome.

Please let me know if you’d like an explanation.

Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.

my wife has 0- blood and i have b- blood . we are planning to have a baby . is there any problem with this blood types ? will the baby have problem or my wife ?
i need an answer because ive heard that with this type of blood there are complications.
waiting for your answer thank you

Dear Tom,

Thanks for writing in.

If your wife’s blood type is O- and if your blood type is B-, you should not have a problem. Dr. Greene discusses this in an article that addresses Blood Type Incompatibility. The problem is only if the mother has Rh- blood and the father has Rh+ blood.

It would be wise to confirm your blood types in case you are actually Rh+. There are medicines that can be taken to deal with blood type incompatibility issues, but they should be given at the appropriate time and confirming your blood types in advance can be helpful.

I hope that helps.
Best, @MsGreene
Note: I am the co-founder of DrGreene.com, but I am not Dr. Greene and I am not a doctor. Please keep that in mind when reading my comments and replies.