Yep, i am..
it's basically.. Where, if your rh positive, your body has the anti-D present already, which are basically attached to your blood cells, however, if you're rh negative, your body doesn't have these, therefore when you get pregnant, if your baby has a positive blood group - some of the baby's blood can leak into yours, and then your body sees the baby as a disease/infection, and therefore fights the baby..
However, the injections will prevent your body seeing the baby as a disease, and you'll both be fine - you shouldn't need it, however if you have a REALLY bad fall contact your midwife as you might need a top up, otherwise you should only need an injection at 28 weeks and at birth (if it turns out your baby is positive blood group) - some midwives give one at 34 weeks as well i think?
If your baby has a negative blood group (like you) you don't actually need the injection, but they can't tell what blood group bubs is, till after they're born, unless the FOB was to be checked - then if they were negative, bubs would deffiantly be a negative, however, if they were positive, you'd not know.
xxxx