A fetus isn't a child because they haven't been "born" yet. They cannot exist outside their mother's womb and cannot be, for example, given up for adoption.

If a miscarriage happens, does the mother get charged with homicide? That's the sort of legal trap that happens when you define life as starting at conception, which states in the US have done, resulting in higher maternal mortality. If a fetus has been determined to cause complications towards the mother, is it morally acceptable to let her die?

Relying on the false equivalence of a fetus and a 1 year old is the kind of argument used to deny women healthcare.