ok... all I know about bp's is that one arm should be different than another because of the way the heart pumps blood through, so every time the midwives take a bp it should be on the same arm, the left. the heart moves the blood around your body in a certain direction so when you take the bp on an extremity like an arm it will differ depending on the direction your blood is going, so if your left arm has a higher bp than your right it might be that your blood is circulating in a sort of anticlock wise motion??? I'm not entirely sure but I think I remember studying something to that effect in bp's in animals for vet nursing...lol... maybe similar...