RH negitive.

Any other mamas RH negitive? This is my second pregnancy, first is now 3 yrs old so its been a while. I understand what the RH factor is, and I understand what the effects can be on a pregnancy without the RhoGAM injections given at 28 weeks and then after birth. My question is, after passing the window of when miscarriages are more likely, after 20 weeks, does the same go for rh neg moms too? Or do we have a higher risk of miscarriage up until receiving the first RhoGAM injections? Does our RH factor not affect the baby before the 28ish week mark? I've never quite understood why the injections are only given so late into pregnancy.