Anti-D Antibody?

I had my first child in January and did not receive my RhoGam shot until 37 week. I had fallen down the stairs earlier in my pregnancy and had l bleeding. The babies blood mixed with mine and now I have the anti-d antibody in my blood. Does anyone know what this is, or what the effects are? I have been told that I may not be able to have more children, but I have an appointment with another doctor coming up in a few months. I was just wondering if anyone else had this, or if anyone could give me links or information. Thanks!!