Actually, I feel that formally adopting one's own child should be the standard procedure.
Why presume or imply something that is so darned important, when far less crucial matters have to be explicitly declared?
If nothing else, that might give them a moment of reflection about the seriousness of the matter and make some of the bureaucratic and legal measures a bit simpler when they become a necessity.
Oh, and in case this wasn't made clear: adoption should be formal, not automatic. We really should let go of the assumption that biological parents must be considered parents no matter what. Quite often they simply are not, will never be, and do not want to attempt to be the true parents, and it is about time we acknowledge that for good and without so much drama and pretense.
Parenthood is a very demanding activity, and many - perhaps even most - who attempt it fail, sometimes quite dramatically. We do not like to say so clearly, but that is the truth.
If the health of families is to be taken seriously, we must let go of the pretense that most couples are somehow fit for parenthood despite what they actually show in their behavior and personalities. More realistic, more responsible and less artificially standardized family models must be adopted.