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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

Blood Groups

89 replies

DiscoLightsOnAFridayNight · 13/01/2022 15:27

I’m not married but will use the in law abbreviations for ease.

I went to a family dinner at my PIL’s house on Saturday and FIL was playing ‘Supermarkets’ with the kids there and he used his blood donor card as a pretend credit card; I noticed that his blood group is A. Now a few years ago MIL and SIL donated blood at a drive I was volunteering at and I know for a fact that they are both blood group A as well. The thing is, my DP is AB.

I did some googling and know there can be rare variations in blood type when the O blood group is involved (either the parents or the resulting children) but as far as I can see random B’s can’t just pop up without a biological parent carrying it, is that right? I didn’t do too well in biology so I’m hoping some of you lovely people can give me a definitive answer either way as I can’t help but jump to conclusions here.

(I left out the +/- as I don’t think they make a difference but can add them if they do).

If the situation is as I suspect though, should I tell DP? There’s a whole complicated backstory involved and I don’t want to cause any trouble but at the same time, I would want to know if it was me and DP is very much that type of person too.

YABU - Leave well enough alone and keep your trap shut.

YANBU - Speak to DP about if it if there isn’t a simple explanation.

Thank you!

OP posts:
BurntToastAgain · 13/01/2022 17:14

@ArnoldBee

Bizarrely I had this situation after going to Blood Donors. I was 17 and I was very upset. It was pre-internet so my poor Dad spent the whole day ringing round people to try and understand to console his poor daughter. It turns out genetic inheritance is not as simple as we are taught at school. The only true way to answer this is of course an ancestry dna test...
Did you turn out to be O?

Because I know I’m OB+ based on my O+ mother and AB+ father. I could only have been OA or OB.

Askingforfriend · 13/01/2022 17:26

I would not keep that secret from DH. If my DH found out I had known and not said anything I imagine he would be very hurt.

ThreeLittleDots · 13/01/2022 17:43

I'd say to him a simple... "Huh... So your mom is an A alongside your Dad, but you're AB aren't you?"

No reason why not to other than colluding in hiding a possibility from him.

ArnoldBee · 13/01/2022 17:50

I'm o negative - both my parents aren't! My eldest is A neg, my youngest is A pos.
I know they're both my parents from ancestry dna!

Georgeskitchen · 13/01/2022 17:52

@Getyourjinglebellsinarow

Nope random Bs don't pop up. Are you sure his dad wasn't using his mums donor card which would rightfully say A and his dad is actually B or AB.

AB children don't come from AA AA parents. I would never ever open this can of worms though if DH is happy with his parents and childhood

Are you a qualified haematologist or did you Google it? My blood group is AB+ Husband A+ our son is B neg 2 other sons one A+, one B+ (Different father to B neg son)
LifesNotEnidBlyton · 13/01/2022 18:25

Going against the grain but I would 100 % tell DP. No way would I want to "go along" with something that I knew might be such a serious lie about DP's whole life. Obviously you don't know 100 % that what you've found out is that his dad isn't his biological dad, but you do now have information that gives you enough of a picture that the likely answer is that he is not. Your loyalty is to your DP, and to not, even unwillingly amd unwittingly, become embroiled in this likely lie around his whole being. You know your DP more than strangers on the internet obviously, but you seem to think he'd want to know. It is totally up to you, and most people seem to think you shouldn't tell him, but my thoughts would be that you should. Because just by knowing this you're not being honest with the man you love and are sharing your life with, the man who is the father of your children (and this is important for their future too, not only because of them and their DF having a right to know who their father/grandfather is but becuase it could be important for genetic diseases etc.... though obviously your DP might not find out who his biological father is anyway, if his dad really isn't.). So I would share what you have found with your partner and let him make the choice what to do.

Darbs76 · 13/01/2022 18:35

If you really want to say something raise it with the MIL. Say I was thinking what you said about your blood group and remembered it’s not possible to have a child that’s AB. See what’s said, you might tell her by reaction if something is amiss

TheVolturi · 13/01/2022 18:46

Yes I remember being told when I was pregnant but I know lots of mums who don't know, I wondered how else you'd know but yes I forgot about blood donors!

chesirecat99 · 13/01/2022 18:56

My blood group is AB+ Husband A+ our son is B neg
2 other sons one A+, one B+ (Different father to B neg son)

That fits with the basic, simplified genetic model that you are taught in GCSE biology, @Georgeskitchen.

Genetics isn't that simple though, @DiscoLightsOnAFridayNight.

It isn't impossible that 2 A parents could have an AB child eg chimerism. Although it isn't relevant here, there is a rare blood group type called the Bombay blood group. People with the phenotype don't express the H antigen, which is needed to make A and B antigen, so even if they are genetically A/B/AB, they don't produce A or B antigens. Most blood type testing looks for the A and B antigens, so even if they are A/B/AB, they will appear to be O.

en.wikipedia.org/wiki/Chimera_(genetics)#Humans
en.wikipedia.org/wiki/Hh_blood_group

The only way to be sure if his father is his father is from a DNA test.

Theunamedcat · 13/01/2022 19:06

Buy him an ancestry kit for his birthday infact buy all of them kits

amylou8 · 13/01/2022 19:25

To have A phenotype your genotype is AA or AO. A and B are co dominant, so the B isn't hiding in the geneotype in the way the recessive O can. It's not possible to get AB offspring from 2 A parents because the gene isn't there to inherited. If it was my husband I would say nothing.

RedWingBoots · 13/01/2022 19:53

@TheVolturi

Yes I remember being told when I was pregnant but I know lots of mums who don't know, I wondered how else you'd know but yes I forgot about blood donors!
@Georgeskitchen they use the A, B and O blood groups to teach you about the basics of genetic inheritance if you do A level or degree level biology courses.
GertrudePerkinsPaperyThing · 13/01/2022 19:58

How do people know their blood type?

From being a blood donor
From having medical treatment or a blood transfusion
If you DM is me, and insists on being told in the maternity ward - I’m glad I did as DS is O- and therefore wouldn’t be able to receive blood from any other group, and has very valuable blood if he chooses to become a donor!

(I’m A-, DD O+ and exh O+ if you’re interested!)

GertrudePerkinsPaperyThing · 13/01/2022 19:59

Also they needed to tell me he was a negative too, because it meant I didn’t need another injection (but I think I had to wheedle the O part out of someone)

Getyourjinglebellsinarow · 13/01/2022 20:16

All you'd be doing is taking the dad he adores away from him though. It's not about his relationship with his mum. She's still his mum. But if he loves his dad and his dad has been a good dad then dna would just muddy that. Who's your dad? The man who impregnated your mother or the man who raised you?

Honestly just try to forget all about it

thetombliboo · 13/01/2022 20:24

I think if there is an issue with DP and his mother then maybe there is a reason behind the way he has been treated and perhaps you have found the answer.
As you said he had counselling then I think if I were you I would 100% tell my husband even though it's hard as he may finally get closure and understand why his childhood was the way it was.

thetombliboo · 13/01/2022 20:27

A lot of replies are about his Dad when perhaps his dad is the biological parent? Or neither unfortunately?
Oh gosh that's so hard but I don't think personally I could keep it from my DH 😔

LakieLady · 13/01/2022 20:37

I know someone who found out that the man he had always thought of as his DF wasn't actually his father at all, when he was in his early 20s.

It was awful, for the whole family, and the relationships never really recovered.

I'd let sleeping dogs lie, personally.

ozymandiusking · 13/01/2022 20:43

It is absolutely NOTHING TO DO WITH YOU.
Leave well alone. It maybe that your partner knows anyway. The fact that you tell him, may make him end his relationship with you.
And No B+ B cannot make an AB blood group

JollyHostess · 13/01/2022 20:54

Could it be that your parents in law had trouble conceiving and used a sperm donor?
If your DH doesn't know by now, I don't see what is to be gained by telling him.
As a PP said, if anything talk to your MIL about it.

MimiDaisy11 · 13/01/2022 21:02

There could be explanations such as sperm donor or some other reason that doesn’t involve some bad reason such as the mum having an affair etc.

It’s a difficult dilemma and I’d hate to be burdened with something like that. It could also be an admin error. I’d leave it and try not to dwell on it.

groeggmeg · 13/01/2022 21:07

The + and - are also somewhat relevant.

Two Rh- parents won’t make a Rh+ baby, but two Rh+ parents can make a Rh- baby. Blood grouping is so extensive and complex.

mumda · 13/01/2022 21:14

@TheVolturi

How do people know their blood type?
The blood bank send you a keyring with it on when they've stolen a pint of it.
Cyw2018 · 13/01/2022 21:17

I think the biggest issue here is that if you hold on to this infomation too long and you DH finds out another way, that the time for him to track down his biological father (if your theory is correct) may have passed. This would possibly be unforegivable.

JollyHostess · 13/01/2022 21:23

@Cyw2018

I think the biggest issue here is that if you hold on to this infomation too long and you DH finds out another way, that the time for him to track down his biological father (if your theory is correct) may have passed. This would possibly be unforegivable.
That is not OP's responsibility though! That's on his mother, if that is in fact the situation.