Declension wrote:
I think that the wrongness of killing something is directly proportional to how intelligent it is.
Fetuses are not as intelligent as a grown human. Therefore, killing a fetus is something like killing an ape, or a dolphin. It's not very nice, but it's not murder. And you are allowed to do it in self-defense, or if letting it live would severely inconvenience you.
Great apes and dolphins have a concept of self and pass the "mirror test". Dolphins are also known to name each other.
They also develop that sense of self around the same age that a human does. However they still have a consciousness before they develop a sense of self, much as a human does.
Additionally, some individuals on the spectrum cannot pass the mirror test.