Expert: Dana Krempels, Ph.D. - 5/18/2010

Question
Hello Dr. Krempels,

I am confused to as why my blood type was wrong on my birth certificate. It said I was B positive. Then I later found out after donating blood several times that I am really A positive. My mom is B positive and my dad is A positive.  She says that her antigens got in me and that is why I tested B positive. Is that really possible? I just would really like to know to clear up some confusion. Thanks!

Answer
Dear Amber,

It would have to take pretty sloppy technique for the hospital staff to mix your blood with your mother's, though there might be some *slight* mixing during birth.  But not enough for a wrong blood test.  It's possible that someone simply wrote it down wrong, or mixed up your results with someone else (a dangerous thing for a newborn baby, if the baby needed a transfusion!  Lucky that didn't happen!).

Your mother is very likely heterozygous for type B and type O blood.  Your father donated one type A allele to you, and your mother gave you her type o allele, making you type Ao.  Since the A allele is dominant, you express type A blood antigens on your blood cell plasma membranes.  So the genetics are all in order.  I think someone may have just messed up your blood type when they tested you at birth.

Hope this helps.

Dana