Quoting Mom of Tristan/Rayah +1:" What is the shot you get at 28 weeks and why do we need to get it? I know this my 3rd pregnancy but ... [snip!] ... If anyone can let me know that would be great. I don't see my Dr until after I get it done so I can't ask him. TIA!"
The Dr basically told me we need it because if any of the baby's blood gets mixed with ours during child birth, your body builds up an immunity to it, so the next time you get pregnant, your body will pretty much attack the baby resulting in a miscarriage.