Why does my birth certificate have blood type listed as just negative?

My birth certificate only has a negative sign in the space marked blood type. I was born in 1994 and my mothers blood type was RH-. What is my blood type if it only has - and is it rare? Thanks.Why does my birth certificate have blood type listed as just negative?
If you see a ( - ) or a ( + ) sign on your blood type, it mostly refers to your Rh blood group, named after the Rhesus monkey from which this blood grouping was first attributed. There are more than 10 ways to classify human blood groups. One is the Rh Blood Group and the ever-famous ABO Blood Group (A, B, O, AB).



Usually, Rh and ABO blood types are put together to further decrease the chance of blood incompatibilities during blood transfusion. Most Americans and Europeans (Caucasians) have Rh negative blood types, while Asians and Negroes have Rh positive blood type. This means that when a person's blood type is Rh negative, his blood does not have the Rh component in his red blood cells. Rh blood group incompatibility is most significant when an Rh negative woman copulates with an Rh positive man. If the resulting infant has Rh positive blood type whose blood leaks into the mother's blood circulation, the Rh negative woman will create antibodies against this component. So the next time that an Rh positive fetus is conceived, the Rh negative woman's blood will attack the second fetus.



This explains why many interracial couples (with an American mother and a non-American father) only have one child.Why does my birth certificate have blood type listed as just negative?
That is your RH type. Since you're mom is Rh negative they always test the baby. If you were Rh positive, and you and your mom's blood mixed while she was pregnant, she could form antibodies to the Rh factor. (also called the D antigen) This wouldn't usually effect the first baby, but if she had more kids that were Rh +, now that she has antibodies built up, they would attack the baby's blood and it could be born with severe anemia or even die.



Mom's with Rh negative blood are given a shot of synthetic anti-D (called rhogam) that prevents them from learning how to make antibodies against it.