Rhesus Negative in Pregnancy

This is a pet peeve of mine. I am rhesus negative and my Ob I used for both births (a very experienced IVF and infertility specialist so he's going to be conservative with this stuff) never bothered with giving me any as I had no bleeding in pregnancy. Instead of the injections he gave me a blood test to check for antibodies forming, of which there were none. The baby's blood circulation is separate to that of the mother. Unless there is reason to believe the blood may have mixed, e.g. though bleeding in pregnancy, if you have had an amnio, after a miscarriage or termination... then you need it. You need it within 72 hours to prevent the antibodies forming. So if you hadn't had any of those, 1. how likely is it that is that the blood is going to mix and 2. how will you know when it happens and when to have the injection in time for 72 hours of the blood mixing?! Its ridiculous! It's a blood product, so its not without risk also. You might like to read Sara Wickham's book which is in my article above... we fall for the old trick that it doesnt matter, its to be sure... but are we introducing an element of risk which we may not need? The pharmaceutical companies get richer...