is it possible for someone to have only RH negative blood ore does it have to have A.B.O attached. Second part can an O negative woman and a O positive man have a B= child?:confused:

Blood type is based on antigens (molecules) that sit on the surface of red blood cells, A,B,AB, or 0. Your blood type identifies which antigens you have from each group. RH factor deals with the fact that some people have the antigens, this makes them RH positive, and some don't, RH negative. As far as the O women and O type man having a B type child, if my Biology memories are correct, No.

Lovelesspa is correct. If you are type O and daddy is type O, chances are baby will be type O. There are exceptions though, and this comes with the type A, B and AB blood types.

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So the baby could be either:

* AB : getting A from mom and B from dad
* A (AO) : getting A from mom and O from dad
* B (BO) : getting O from mom and B from dad
* O (OO) : getting O from mom and O from dad

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Here is a website that breaks it down rather easily. Baby's Blood Type - Keep Kids Healthy

I don't understand what you mean by a B= though. Do you mean that the negative from the Mom and the positive from the Dad cancel out? If so, no that is not how it works. If Mom is O- and Dad is O+, then baby will either be O- OR O+. If baby is a + Rh factor and baby is a - Rh factor, then mom will have to have a RhoGHam shot with subsequent pregnancies.