Are you talking about an ab negative blood type, as in you are rh negative? I you are then the shots you are talking about are rhogam shots, they are given to women with rh neg. Blood ( only 15% of the population is) if the daddy has a positive blood type. This is to prevent antibodies from forming in your blood if you are carrying a baby with a positive blood type. They are usually given in the 20 something week of pregnancy, after miscarraiges, amniosyntisas, or injury to the abdomen that could of caused the babys blood to leak into yours. Also after you have the baby, you will be given another shot if the baby has been determined to have the positive blood type. These are very important, because if you do build antibodies to that blood, your body will attack the embryo and cause miscarraige or rh disease in the baby and he might die or need a blood transfusion. I have the shots and they do hurt a little but thats all! No big deal just do it. If the daddy is neg. You wont have to have them! You can read all about it in any pregnancy book. Good luck
tbf