RH- miscarriage prevention

Katie and I are both RH-, which means miscarriage can occur if blood from the pregnancy mixes with blood from the mother. Katie mentioned yesterday evening that her doctor informed her she needs to go to the ER immediately if she has any bleeding (including normal implantation bleeding) as it can cause a miscarriage if she doesn't get the RH shot.

... Well, of course my first thought was "that would have been good to know". And a burst of anger. And sadness. It's possible mine could have been prevented had we known that. Of course I can't say that to her - she'd feel awful and afraid to talk to me about her pregnancy. So, I'm writing it out so I can process it later. Now is not the time for these emotions.