“fully formed baby” is not a thing. From conception to death, no matter how old, the body is continuously changing form. Neither the rapidity nor the proportion of that change is relevant to its type.
What doesn’t change, and is there from conception, is that it is a living human being. With DNA from one male and one female human being what else could it be?
It is the same for all living beings. All will be a living being of the same type as its parents from the moment the DNA of its parents conjoins and the life processes begin.
There is no magic moment other than conception when a a pig becomes a pig or a duck becomes a duck or when a human becomes a human.
Well stated.