Where does the baby get its blood group from???

Mum and Dad?

Ok so i'm O+ she's O- where does that the baby

it can be either (-) or (+)
I'm O- but Oscar is (+)

O + O = O
A + B = AB
B + B = B
A + A = A

+ and - vary though

I've not heard of OB or OA

what happens with O + A and the like

OA and OB are automatically O, I think lol

Actually it's a lot more complicated than that. It's all to do with recessive genes etc. For example, I am B+ and my OH is A+ but Kaya is O+. What you do have to know though is that if your OH is Negative but the baby is Positive she will need a resus injection after she gives birth or it could seriously affect her future chances of conceving. However, her doctor/midwive should explain this to her.

I'm A-
OH is O+
DD is O-