Are they really my parents?

Question

If both of my parents have O positive blood, is it possible for me to have O negative blood? I have been told that it is not possible, that one parent would have to have the negative factor. I have been researching this question for some time with no good answer. I would really appreciate your help in answering this.
Debbie Howlett – Farmington, New Mexico

Dr. Greene's Answer

Genetics can be so confusing! I can easily see how after much research the issue about your parents would still appear murky.

The modern science of genetics had its start in 1866 when an Austrian monk named Gregor Mendel provided a simple yet powerful description of how traits are passed on from one generation to another. Mendel’s work was unappreciated until 1900 — more than fifteen years after his death. In his initial formulation, he described how sexual beings get two genes for each trait, one from each parent. The trait expressed, or visible, is a result of the interplay between these two genes. Specifically, he recognized that some genes are dominant and some are recessive. If you have one copy of a dominant gene you will express that trait, regardless of the other gene. In order to express a recessive trait you must have two recessive genes.

Mendel’s first experiments, though simple, were quite profound. He worked with peas, which had easily distinguishable traits, such as green versus yellow seeds. Each pea has two seed-color genes, one from each parent. The peas with two yellow genes were yellow. Those with a yellow and a green gene were also yellow; only those with two green genes turned out to be to green. Thus yellow was dominant over the recessive green gene.

The situation with human blood genetics is far more complex, since at each point there are multiple possible characteristics. Nevertheless, the genetics of human blood is far better understood than that of any other human tissue. While there are rare exceptions, the following information on blood types applies to most people.

First, let’s look at the ABO blood types. Each person receives an A, B, or O gene from each parent. In this system, the A and B genes are co-dominant and the O gene is recessive. Thus, a person whose genetic type is either AA or AO will have blood type A, those with genetic type BB or BO will have blood type B, and only those genetic type OO will have blood type O. This means that a child with type O blood could have parents with type A, type B, or type O blood (but not with type AB). Conversely, if two parents both have type O blood, all their children will have type O blood.

Another medically important blood type is described in the Rh system. These genes were first discovered in the rhesus monkey, hence the designation Rh. The Rh system is actually far more complex than the ABO system in that there are 35 different possibilities that one could inherit from each parent. These, however, are roughly grouped into positive and negative types. In this system the positive are dominant over the negative. If your genetic type is ++ or +-, your blood type will be Rh positive. Only if your genetic type is — will you be Rh negative. This means that if both parents have Rh+ blood with the +- genes, they could have children who are ++, +-, or –. In other words, their children could be either Rh positive or Rh negative. Children who are Rh negative can have parents who are either Rh positive or Rh negative.

Two parents who have O positive blood could easily have a child who is O negative. In fact, most children who are O negative have parents who are positive, since the +- combination is so much more common than the — combination.

As it turns out, there are more than a dozen complete blood group systems other than the ABO system and the Rh system. This makes great precision possible in looking at inheritance and family trees.

There is no reason, based on your blood type, to suspect that your parents might not really be your parents. If questions linger for other reasons, specific tests are available through blood banks and private laboratories that can settle the issue. These tests are commonly known as paternity and maternity DNA testing (for father and mother respectively). Given the billions of unique people on this planet, the power and precision of genetic testing are amazing.

Medical Review on: April 15, 2009
About the Author
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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

I am A positive and my ex-husband has rh positive blood.
I had an affair with a man who is O positive.
My daughter is A negative.
Which one is likely to be the father.

Dear KE,

Thanks for writing in.

Sometimes you can eliminate a potential father, based on blood type, but it is impossible to determine paternity from blood type. If you have A-positive blood, and if your ex-husband has Rh-positive blood, and if the man you had an affair with has O-positive blood and if your daughter has A-negative blood, either man could be the father. The information you have does NOT eliminate either man.

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.

My husband and I both have A Negative blood types. Does that mean our children also have A Negative blood? My child of 29 years has multiple health problems. Could this be the reason?

Hi Janie,

If a person is Rh negative it means they do not have the D antigen in their blood. If both parents are Rh-negative, their children will also be Rh-negative. If one or both parents are Rh-positive, their children can be either Rh-negative or Rh-positive.

This could not be a reason your son has multiple health problems. The only time this is an issue is if the mother is Rh-negative and the father is Rh-positive and the mother does not get medical treatment for following her first pregnancy.

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 wife are A+. Our first born is A+ but our 2nd child is O+. Is that possible? Thank you

Hi Lorenzo,

Yes! This is possible. In fact if two parents have type A+ blood, there is a 93.75% chance each of their children will be Rh+, a 93.75% chance each child will have type A blood, and a 6.25% chance each child will have type O 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.

my dad is AB negative and my mom is O positive and my blood group is A positive are they my parents

Hi Hana,

Blood types can not determine if two people are your parents or not, but in some instances, they can determine that two people aren’t your parents. In other words, there are a lot of people with the same combination of blood types, so blood types can only say “this combination is a possibility or is not a possibility”.

In the situation you describe, if your dad has AB- blood and if your mom has O+ blood, and if you have A+ blood, they could be your parents.

Each parent gets one allele from each parent. In this example, the child got an A from the father and an O from the mother and would have AO blood type. We call that type A blood. If either parent is Rh+ and passes that down to their child, the child’s blood is Rh+.

If you still have questions about paternity, DNA testing will provide the answers. Blood typing will not.

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’m curious on do the dad and child suppose to have the same blood type . I’m O+ he’s O- and my child is O-

Hi Ni’Julum,

Each child gets half the code for their blood type from each parent. In some cases that means the child has a different blood type than either parent because it’s a combination of the two.

If one parent has O+ blood and the other has O- blood, their children can be either O+ or O-. Both are completely normal.

Please let me know if you’d like a more indepth answer.

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’m curious after reading this thread. I am O+ but both of my parents aren’t. I have 3 siblings and I’m the only one that’s O+
I have health issues and I’m starting to feel freaked out. Hopefully I can get some answers. Thank you.

Hi Danielle,

I doubt there’s a reason to freak out. If you are O+, your parents could be O+, O-, A+, A-, B+ or B-. The only blood type that neither one of them could have is AB+ or AB-.

If you’d like to know more about why that is, 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 dad was o positive my mom is o negative with rh negative. I am A negative with rh negative. Is this possible?

Hi Dana,

Thanks for writing in.

Our current understanding of genetics is that it is not possible for two parents with type O blood to have a child with type A blood. However, it’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested.

If you want further explanation, please let me know.

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
I am B negative – RH negative. My mother is B Positive and my father was AB Positive. How am I RH Negative if both my parents were Positive?

Hi Sandya,

This can be very confusing, but just because both parents are Rh-positive, they don’t necessarily pass it down to their children, in fact, there is a 6.25% chance that each of their children will be Rh-negative.

If you have further questions, 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.

Hi I’m blood type B+ and so are my two younger siblings however my father is blood type A+ and my mother is blood type O+ is this possible?

Hi Joshua,

Thanks for writing in.

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 O+ blood and their child to have type B+ blood. Parents with these two blood types could have children with blood types: O+, O-, A+ or A-.

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.

Hi, Is it possible for me to have O+ blood if my Mom is B+ and my Dad is O+?

Hi Jadon,

YES! This is a very normal 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.

Hi my blood type is 0 neg and my sister is A pos , my father is 0 neg, not 100% sure about my mother (deceased) but I think she was o neg as well , is it possible that my sister could be my fathers daughter or due to her blood type would her father be different

Hi, I’m so confused in how to know my mother’s blood type and my biological father’s blood type, my half brother’s blood type is RH positive and mine is O positive, and I don’t know what my half brother’s father’s blood was either

Hi Karen,

Every child gets one allele for blood type from each parent. It doesn’t matter which parent provides which allele.

If your father has type O- blood, he’s not ruled out as the father of a child with A+ blood — if the child’s mother had type A+ or AB+ blood.

If the mother had type O-, then she could not have a child with A+ blood — unless the father had type A+ or AB+ blood.

Since you don’t know your mother’s blood type for sure, you can’t make any conclusive determination about your or your sister’s parentage.

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 is A-, my dad is O+. I’m also A- like my mom, but my sister is AB+. When I was studying blood types, it stood out to me that my sister’s blood type compatibility didn’t match the chart I was looking at.

It’s to my understanding that AB+ blood with A- and O+ parents isn’t even supposed to be possible. I confronted my mother years ago about it and got no clear answers. She was angry with me for questioning it and told me to drop it.

Another odd thing: My mom has blue eyes, my dad has green eyes. I have blue eyes like my mother. My sister has dark brown eyes. So, there’s the seemingly impossible bloodtype combo and nearly impossible eye color combo.

I seriously don’t think we have the same father. I think we’ve been lied to. I stopped questioning our mother because she refused to discuss it. I will always think it’s suspicious though. What are your thoughts? Could it be possible for her to be AB+ and have A- and O+ parents…even a small chance?

Hi Janie,

Our current understanding of genetics is that it is not possible for one parent to be A-, the other parent to be O+ and their child to be AB+. If your parents do have A- blood and O+ blood, they could have children have O+, O- A+ or A- blood.

It’s not uncommon for blood types to be different than they are thought, but your mother’s attitude likely makes this impossible.

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’m a RH negative mom and my husband is AB negative. Our child is O positive. We went to the blood bank and asked them what blood type are child would be. They said that the blood type could be O AB A B negative but it could also be O AB A B positive. Now this was 40 years ago. They said this is because they are rare blood Types.

My father is o positive and my mother is AB negative and me and my sister both are 0 positive to my understanding I should be neither A or B and there is no chance I can be o positive

Hi Carolyn,

Forty years is a long time. Perhaps the blood bank then didn’t know as much as we know now, or perhaps your memory of what they said is a bit foggy.

Here is our current understanding:

  • A parent with AB- blood can only have children that have type A or B or AB blood, depending on the blood type of the other parent.
  • Two Rh- parents can’t have a child with Rh+ blood
  • Type AB blood is the rarest type
  • The only combination of parents that could result in any possible outcome (O+, O-, A+, A-, B+, B-, AB+, AB-) is one parent with type A blood and the other with type B blood and at least one parent that is Rh+, but the other could be Rh+ or -.

If you are still curious, you’ll need to have new blood type tests for the three of you.

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.

Very nice one
I love that

plz give me the answer,if parents both are Rh positive,then their child will be?

Hello,

If both parents are Rh+ their children can be Rh+ or Rh-. If one parent is Rh+ and the other is Rh-, their children can be Rh+ or Rh-. But if both parents are Rh-, their children can only be 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 can you help me sir. My mother and my father is same type o. And my brother and sister is type o. But only me is type b+.

Nika,

Our current understanding of genetics is that it is not possible for two parents with type O blood to have a child with type B blood.

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.

My sister-in-law is has AB blood, her mother is O+ and her father is O-. Both her siblings have O blood. How does she have AB?

If I am B- my sister is AB- and my other sister is O- our mother is A- what is my father’s blood type?

Hi Amy,

From all the science and testing we have now, it is believed that two parents with type O blood, can not have a child with type AB blood. There is no reason to think that science is in question.

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 mother is A- I’m O positive, my brother is O- what is our fathers blood type ?

Hi Jackie,

If your mother’s blood type is A- and if you are O+ and your brother is O-, and if you have the same father, he could have A+, B+ or O+ blood.

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.

Hello,

I am O+, my Mother is B- and my Father is A+. My Mother says it is impossible for me to have O+ blood and I should get re tested is this correct ?
Thank you

Hi Christy,

Thanks for writing in with your question.

If your mother has B- blood and your father has A+ blood there is a 6.25% each of their children will have type O blood and a 75% chance each child will be Rh+.

If you’d like an explanation of why that is, 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.

Hello…

I keep reading everything that you have written on this page and in the comments, and I guess I just need to hear it again? I am B+ and both of my parents are O+. Both of my parents have had cancer and extensive blood work, and I have had my blood work done numerous times. Does this really mean my father isn’t my genetic father? I am scared to get a genetic test… but I can’t stop thinking about it… He never liked me as much as my brother, but my mom told me he was and if he wasn’t, she took it with her when she passed.

Hi HR,

You are right, as far as we know, two parents with type O blood can’t have a child with type B blood. There are extremely rare cases, that I doubt fit your circumstances, where a person with reported type O blood actually has type hh (Bombay). Our test results can’t differentiate between OO and hh, so they are read as O. BUT this wouldn’t result in type B blood in the child. Might there be some other wild anomaly? Something that is ahead of our blood typing technology? If so, that should show up on DNA testing.

Here’s the thing — if your mother is no longer living, you can’t ask her. That means to get any more clarification you would need to talk to your father and perhaps even do a DNA test. What will it do to your relationship with your father if he finds out for the first time that you are not his child? Or maybe he knows and just talking about it will help you both? I don’t know if there’s a way to predict the outcome. It may come down to figuring out what you can live with and what you can not.

Sorry I couldn’t be more 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 mother blood is o positive.and father blood is o negative then what will be the blood of children

Hi Kailash,

Thanks for writing in.

If one parent is O+ and the other is O-, all their children will have type O blood.

If they had 100 children (which no two people will have) 75 would have O+ blood type and 25 would have O- blood. If they have two children, it would be perfectly normal for them to be either O+ or O-. The averages only apply over large groups.

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.

Hi, I’ve donated blood in the past and it came to me as a surprise that I’m O+, but both of my parents are O-. It that even possible?

Hi Gavin,

Thanks for your question.

Our current understanding of genetics is that it is not possible for two Rh- parents to have a child with Rh+ blood. The Rh+ means the blood is positive for the D Antigen. If neither parent is positive, they can’t pass it along to their children.

However, 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 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.

If a mother is A+ and a Father is A+, how likely is it they will have two children who are O+? My parents have always told us they are A+. My sister recently got typed as part of a pre nursing health class. Her type came out as O+. I was curious so I ordered an at home blood test (Eldon Home Kit HKA 2511-1) and the test shows I am O+.

Hi Elixabeth,

If both parents have A+ blood, the likelihood that each of their children will have type O blood is 6.25%. (That means if they had 400 children, 25 of them would have type O blood.)

The likelihood that each child will be RH+ is 93.75%.

Like tossing coins to see how many heads and how many tails, the number averages out after a lot of throws, but the first few may all be the same.

In other words, there’s not reason so suspect two A+ parents aren’t the parents of two O+ kids.

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 is normal to get the blood type of both parents? I’m ab positive. My parents are a positive and b positive? Is combining both blood types common?

Hi Bella,
Thanks for your questions.
It’s not only normal, it is the way it works. Every person gets one blood type gene (in the form of alleles) from each parent. This can be confusing because blood type names don’t always indicate what alleles each type has. As an example, blood type B can have B and O alleles, but they always have at least one B allele. Type A can have A and O alleles, but they always have at least one A allele.
If your parents and type A and type B, they could have children with type AB, A, B or O blood.
I hope this is helpful,
@MsGreene

Is it possible for a child to have AB negative blood when the father is AB positive and the mother is A positive?

Hi Nahian,

Yes, it is possible. In fact, there is a 37.5% chance their child will have AB blood type and a 6.25% chance their child will be Rh negative.

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

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.

Sir, Me and my wife are O positive but our child is A Positive. Is it Possible ??

Rohan,

Thanks for writing in.

Our current understanding of genetics is that it is not possible for both parents to have O+ blood and their child to be A+. An O parent can only have children who have type O blood.

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

There is, however, 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.

That means if either you or your wife had the Bombay type, those results would read as type O even if they weren’t and that would throw everything off. This would be extremely rare.

DNA paternity tests are considered accurate (99.999%) and are considered the only accurate test for paternity. If you want to pursue this further, a DNA test is 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.

Is it possible if I am A positive that my parents are A positive and O positive?

Hi Wendy,

Yes, it is completely normal for an A+ parent and an O+ parent to have an A+ child.

If you have questions about 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.

I just found out that I’m B+, my father is O+ and mother is RH O. How am I B+?

Dear Melanie,

Our current understanding of genetics is that it is not possible for both parents to have type O blood and their child to have type B blood. Two parents with type O blood, can only have children with type O blood.

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 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.

Well Think I must say this then…it is possible for newer scientific research into blood groups. My daughter is B+ I am O+ and her father is O- and she is DEFINITELY ours. So it IS possible for O parents to have a B child or NON “O” child.

Please could you tell me if an o positive mother could have a b negative child, blood group of the father unknown, thank you.

I am Rh neg Why did this not affect my first child?

Hi Sandy,

Dr. Greene wrote a whole article about this. Here are a few excerpts:

“People are called Rh-negative if they do not have the rhesus (Rh) protein on the surfaces of their blood cells. If Rh-positive blood cells get into the bloodstream of someone who is Rh-negative, the body of that Rh-negative person will see this as an enemy invasion.

Unprepared, the Rh-negative person will begin to make antibodies (what you call anticorps) against the foreign Rh protein. This first exposure is often not even noticed. The next time an exposure occurs, though, the body is primed to seek and destroy all Rh-positive blood cells. All-out war can occur inside an Rh-negative person’s body…The first pregnancy is rarely a problem because blood is often not exchanged until the time of birth.”

You can read more about How To Determine and Manage Rh Incompatibility in his article.

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.

Is it possible for A+ and O- to make O+

Hi Ashley,

Yes, it is possible for one parent to have A+ blood, the other to have O- blood and their child to have O+ blood. In fact, there is a 25% chance the child will have type O blood and a 75% chance he or she will be Rh+.

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

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 husband is O negative, and I am B negative. My first child is B+. We’ve had his blood drawn three different times, and it always comes back B+. How is this possible?

Hi Kate,

If a person has Rh- blood that means the D antigen is not present. Rh+ blood means the D antigen is present. Theoretically, if neither parent has the D antigen in their blood, they can not pass it along to their child.

You might consider having both parent’s blood retested. If all the results come back the same, you might consider a DNA test for all three parties.

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.

If Mother is B- and father is O+, can i (child) be A+?

Dear Jennifer,

Our current understanding of blood types is if one parent is B- and the other parent is O+, they can not have a child with A+ blood. Their child could have Rh+ blood, but not type A.

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

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 cannot find any information about 0+ parents having an RH- baby, both my Husband and I are 0+ and my daughter is RH-, could you please explain how this was possible, she is 35 now and when she was born the nurse tried telling me that it was impossible for her to be her father’s and I told her that she was wrong, that he was her father and that she needed to do some research to show that to be true. Well she came back to me two days later and confirmed that while it is possible, it is as rare as an RH- blood type.

Hi Rhonda,

It is perfectly normal for two O+ parents to have an O- child. Rh+ means the presence of the D antigen. Rh- means the absence of the D antigen. 6.25% of children with two Rh+ children are Rh-. On the other hand, two parents that are Rh- do not carry the D Antigen and can not have a child that is Rh+. Sounds like your nurse had the two mixed up.

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,
I am O+ and my wife is A. Our daughter is AB negative. Is this possible?

Hi Johnny,

If one parent is O+ and the other is A, they can have children that are A+, A-, O+ or O-. They can not have a child that is AB- or AB+.

Before jumping to any conclusions, it’s wise to have all your blood retested. It’s not uncommon for blood types to be different than people think they are. If there’s still a question after retesting, 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.

Hello! Is it possible that both of my parents are A and I am AB?????

Hi SW,

First, it is 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.

With that in mind, it is not possible for two parents with type A blood to have a child with type AB blood. Two type A parents can have children that are type A or O.

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.

I am having B- blood group and my brother also having the same but my mother is O+ and my father is A+ so how is it possible that me and my brother are B- please help me to determine that they are my actual parents or not. Your help will be appreciable.

Hello Sneha,

It’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested before making an assumption of this size, but our current understanding of genetics is that it is not possible for one parent to be O+, the other parent to be A- and their child to be B-.

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.

SO i want to ask this since im seeing this now. my mom is o+ and my dad is a or b something how is it that im O+ as my mom?

Hi Whitney,

First, it is normal for the child of parents who have type A or B blood to have type O bloood. Here’s why…

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.
— If a person is Rh+, he or she can have a child that is Rh+ or Rh-.
— If a person is Rh-, he or she can only have a child that is Rh+ if the other parent is Rh+.
— Two parents with Rh- blood can not have a child with Rh+ blood.
— Two parents with Rh+ blood can have children with Rh+ or Rh- blood.

What all this means is if your mom is O+ and if your dad is A or B they could each pass down an O allele and your mom could pass down the D antigen and they could have a child who is O+. That would be perfectly normal.

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 father to be o- and mother to be AB and have a B Rh + child?

Hi LeeAnn,

Yes, it is possible for one parent to have type AB blood, the other parent to have type O blood and their child to have type B blood. At least one parent must be RH+ for their child to be RH+. In this case, if the mother was RB+ and if the father was O- the child could be B+.

If you’d like an explanation of how that works, let me know.
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.

If the mother is O Negative and the baby is O Negative could the Father be either a positive or B positive

Hi Sedona,

Thanks for writing in.

If a mother is O- and the father is A+, their baby could be O-. If the mother is O- and the father is B+, their baby could also be O-. In fact, if a mother is O- the father could be Rh+ or Rh- and only blood group the father could not be is AB.

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 mother is A- and has a baby that is O+, who would be the father? Father with O+ blood type of father with B+ blood type?

Hi Lrey,

In this situation, if the mother has A- blood and if the baby has O+ blood, neither man with O+ or B+ blood can be ruled out. In other words, the father could be either man.

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.

Hi, I don’t know my parents’ blood types, and both have passed.

My sister is RH negative, as is her daughter.

I’m O positive. Is this possible?

Hi Susan,
It is possible for the same two parents to have children who are Rh+ and Rh-, with one exception. If both parents are Rh-, they can only have Rh- children. Likely your parents were either Rh+ and Rh+ or Rh+ and 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. I always thought I had an O blood type but getting hospitalized after an accident revealed I was actually B+. If my mom is O+ and my dad is O+ and all my siblings are O+, how did I become B+?

Hi Lovely,

Our current understanding of genetics is that it is not possible for two parents with type O blood to have a child with type B blood. If both your parents are O+, they could have children with O+ or O- blood, but 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.

Hi Dr. Greene,

Is it possible for a mother and father that both have type B blood to have a child is with type A blood and another child with type O blood?

Hi Bethany,

Our current understanding of genetics is that it is not possible two parents with type B blood to have a child with type A blood, but they can have a child with type O blood.

It’s not uncommon for blood types to be different than they are thought. It is wise to have both parents and the child with type B 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.

Hello Dr.
I just want to ask, can a mother with AB + blood group give birth to O + in any case??

Gautam,

Our current understanding of genetics is that it is not possible for one parent to be AB+ parent to have a child that is O+.

Can a mother with AB+ blood give birth to a child with O+ blood in any case? There is a very rare blood type, called Bombay, that falls outside the ABO system. If a person has that type, he or she shows up as type O, but both parents must be carriers. I don’t think that would fit with an AB blood type.

In this case, it would be wise to have all your blood retested. It’s not uncommon for blood types to be different than they are thought. 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.

Mother O-. Two kids AB-, other three kids A-. How is it possible that she is the mother of the AB- kids?? Her blood has been tested multiple times. She had to have a transfusion when she gave birth to my oldest sister and they had to have type O- transported in because they did not have any in the local blood banks. (1959)
I wonder if she is really type A but keeps retesting as type O for some reason. Is that possible?? Maybe the transfusion worked out because O- is the universal donor. Scratching my head.

Rox,

That is very curious. 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 Bombay or 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 your mother may have the Bombay blood type she can talk to her doctor about a specialized test for this blood type as it does not show up using the normal ABO blood type tests.

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

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.

Mother is o positive dad is a negative, can child be o positive

Dr: Green,

Both of my parents (supposed) are O+, my blood type and s A-, what is the probability of this. It should be noted my brother is O+.

Hi Robert,

Yes! If one parent is O+ and the other is A-, their children can be O+.

Here is a list of the blood types their children can have:
— O+
— O-
— A+
— 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.

If my mom is A+ and my father O-then is it possible for them to have a child with AB?

Hi Kim,

Thanks for your question.

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

It is wise to have all three blood types 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.

Hello, can i ask if my father was AB neg and my mother was 0 positive why I have 0 neg blood, both my sisters are A neg and B neg, this makes my dad not my biological father right???.

Hi Kat,

Thanks for writing in.

You are correct that a parent with type AB blood can’t have a child with type O blood. But it’s not uncommon for blood types to be different than they are thought. It is wise to have all your blood retested before drawing 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.

Hi
Can A- father and AB+ mother have o+ child

Dear Alok,

This is a very interesting question. If a parent has A- blood, he or she can have a child with O+ blood, if the other parent is Rh+. But a parent with AB+ blood can not have a child with O+ blood. A person with AB blood can only have children with A, B or AB blood (depending on the blood type of the other parent).

It’s likely 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.