N.K.
I was in my first trimester, just a month ago, when I lost my little baby, and I want to do something like that myself. It probably depends on the person, but I would have loved it.
To me, as soon as I found out I was having another baby, it truly was my baby. Even if I was only a few weeks pregnant, it was already a person to me. It's a very nice idea. If you want to make it a little less "personal" (for lack of better words), maybe try a rose bush, or something. My mother planted a rose bush in her garden each time one of her children graduated highschool, and I love that idea for representing a child.
Good luck!