Can someone give me information on parental ABO blood types and the different possible outcomes?

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emilyosu

New member
UPDATE: it was the most likely answer. Grandma was wrong, dad is B+.

I’m not sure where else to ask, and it looks like this might be my best bet! I was always under the impression that O+ and O+ would make another O+ but kiddo is apparently B+! From what I’ve read, that suggests that: one of us is a chimera, or has cis-ab or Bombay blood types. It’s unlikely baby is a chimera/absorbed a twin since in theory that twin would have also been O+. I suppose the simple answer would be that they got his results mixed up in the hospital but I’m not sure how likely that is.

None of this actually matters in the long run (I don’t think it does, anyway?) but I do find it fascinating. If anyone has any research regarding unexpected blood types, share it here!

Edit: yes, he is unquestionably by husband’s baby. I figured the most likely answer would be either my husband was wrong about his own blood type or there was a lab mixup. Definitely my baby, though, he’s my twin.
 
@emilyosu Have your and your husband’s blood retested as well. My mom always thought she was B+ and my dad was O+. When I had my baby I joked about my son and I both getting an A+ on our tests. She had a big “Wait a minute…” moment 😄 I thought there was a decent chance she was a chimera based on some other health issues but it was just a boring mistake many years earlier when she had me. She’s A+ as well.
 
@damacri Same here. I found it really interesting how shocked I was, hilariously. Like it was somehow part of my identity. Might have been the pregnancy hormones though…
 
@emilyosu As another person said, O+ and O+ can only make O+ or O-, barring the incredibly rare possibility of a spontaneous mutation in baby's DNA. I've got general biology higher education training but I don't specialise in blood or genetics so happy to be corrected by someone more knowledgeable about other rare possibilities.

Chimera (edit: chimerism in the baby wouldn't, chimerism in you detailed in comment below), cis AB and Bombay still wouldn't give baby B type blood in your scenario. If you're certain the biological parents are both O+, I'd be looking into lab mix ups.

It does matter if baby ever needs a blood transfusion (if baby is actually O+ they can't receive B+ blood) and it does matter if baby is a girl and has her own baby one day (if she's actually O- and her baby is a + type there's additional medical steps involved).
 
@niansboog If a parent is mosaic and has O in their bone marrow but B in their gonads then that would do it? I don’t know the specific genes or chromosome locus for blood type, but genes do weird things
 
@elizabeda777 Mosaics don't apply to the ABO classification (they're in the RhD group). If the parent was a chimera as you describe, that's possible - to have DNA with O blood, but DNA with B blood in the reproductive organs, and pass that on to the baby. At least one grandparent would need to have B or AB blood. It's worth noting that there are about 100 cases of chimerism described in medical literature - at least 3 have had different DNA in their reproductive organs than in their saliva (or whatever was used for a parental DNA test). So even accounting for the fact that because it's hard to find, it's more common than described, it would still be very rare.
 
@emilyosu Def have those blood types double checked. One of my friends had a kid with a blood type that didn’t make sense and it turned out her husband’s was incorrect all along- from the military!

We’re an all O- family and my understanding was the kids also had to be O-
 
@emilyosu I have a feeling the best bet is that your husband got his own blood type wrong. O is the absence of both A and B so no one would have the B gene to pass it on. It's also possible for some reason one of you have the B gene and it's not expressing.
 
@keekjaci Not expressing is interesting! That’s where I’m under the impression parental chimerism can come into play. Husband said he’ll request his blood type the next time he needs blood work done, and I’m asking the ped about kid’s tomorrow. If we ARE a rare case it’ll be interesting to see if we can find out what happened.
 
@emilyosu When is the last time you and husband were typed? My brother was given a blood test at birth and told her was B and actually ended up being O years later. My mom was insane over it. Apparently sometimes at birth the baby can be typed as the parent’s blood type instead but a few weeks later will test as their own blood type. Maybe one of you was tested as birth and given the wrong blood type.
 
@mikeysavedbygrace Side story to that- I was in the hospital for a month while pregnant this year and hospital policy required me to have my blood type checked every 3 days, as if it was going to change. I’d ask about the result each time to mess with the docs/nurses lol
 
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