And this is the blood vessel of our mother. Now, normally, because the red blood cells are too large, they cannot pass across the placental membrane. But during pregnancy, during childbirth, that is, there is a small likelihood that there can be exchange of red blood cells. There is a leakage of red blood cells and some of the red blood cells can be exchanged between the fetus and Arab woman. Now, we know that because the woman is RH negative that means within the bloodstream the woman will not have any antibodies against antigen D because that woman was never exposed to antigen D before that. And so she is RH negative.