does anybody know what the rh negative shot does
It's to prevent your body from attacking the baby if you are rh- and the baby could be rh+.
Basically if mom is rh- and dad is rh+, the baby could potentially be rh+ as well. Because moms body has never produced the rh+ enzyme, the immune system will treat it like any bacteria or virus and fight against it. The rhogram(?) Shot is supposed to prevent mom's body from doing this and fighting against the baby.