I was recently talking to my mother and she told me that when I was born a doctor informed her to make sure I didnt marry someone of the same blood type as me, since this would worsen the chances of having a healthy child? Is this true? I can't seem to find any biological basis for this. By the way, I am O+ type blood. My mom is O-, and my father is O+. I know she had to get a shot because of this RH incompatibility with my father.