When you’re pregnant, you may learn that your baby isn’t your type — blood type, that is. Every person is born with a blood type — O, A, B, or AB. And they’re also born with a Rhesus (Rh) factor, ...

Different blood types are prevalent in different parts of the world. In the United States, AB-negative is the rarest blood type, while O-positive is the most common. Your blood type is based on ...

The rhesus factor, or Rh factor, is a protein that may be present on the surface of red blood cells (RBCs). If RBCs contain the Rh antigen, they are Rh-positive, and if not, they are Rh-negative. It ...