Oh, but the baby boost does work for me. Every time they try a baby and don't succeed I get the doctors appointment, apply baby boost and they always have babies after that.
If it's all but coincidence, that I do not know.
I could be wrong about this, but I think if you give the baby boost as a result of a doctor recommendation, it may work better than if you just give it to them without consulting the doctor first. At least it seems to work that way in my games.