Im researching methods of bc for us. Dh and I have decided to wait 5yrs before thinking about having another dc. It has always been my assumption that IUD's worked primarily by not allowing a fertilized egg to implant? Is this true? I was reading about Mirena today....and it seems that it works mostly by preventing a release of an egg, and by thickening the cervical mucous so sperm cannot enter. I want to find a BC method that is convenient, yet wont prevent implantation of a fertilized egg...that is very important to dh and I. Mirena seems like an option for us, but I really want to make sure it does not do that.