I have negative blood type and had several pregnancies that I was fine with- one miscarriage and then one other pregnancy after that- he's four months old now. When you have RH negative you will need to get a shot for each pregnancy and after a baby is born, they test their blood type, if they are positive, they give you another shot. For my pregnancy after my miscarriage and my miscarriage, I had spotting and they brought me in for a shot right away instead of waiting for the 'standard 28 weeks'.