Yve, I like what you said about how a lot of the things we discussed turn the birth mother in to an incubator. It needs to be clear to the child that they were born to another person, and if an adoptive mom is treating ultrasounds and things like that as her own, it has the potential to be pretty confusing to the adoptee.
This is an extremely helpful thing to know, we are hoping to foster and possibly adopt my nephew, and we've explained the situation to all three of our children (ages 9, 7, and 4) and they all understand that once he is in our home he will be their BROTHER, not foster brother, not cousin brother, nothing that will make him feel different or alienated. But with my youngest son I tried to be sure to explain in simple terms that his new brother would not be coming from my tummy, but from another mommy's tummy. The other mommy still loves him very much though, so she might want him back, but maybe we will have him forever, etc. I expect we will have similar talks with the baby once he is old enough to understand. It's very hard to explain all of this to each child how they will be able to comprehend it. I don't ever want to say anything in a way that will disconnect my nephew emotionally from my sister, or that will infer that she doesn't love him or didn't want him, because I know that in her heart she does. I don't want to hide anything from him. However I want, from the beginning, to place him into our family as our son, as our children's brother, even if adoption isn't on the table right now, even if it's something that won't come up for a long time, I know the reality of the situation and I know the likelihood of that and I want him to always feel the love and family bond that every child should. I also want his mother to have the comfort of knowing that he has this family here, but that he won't lose the knowledge of his origin, should she ever check in.