Then why did you compare it to a leg?

Because a leg too is part of human life? You were the one trying to make unscientific claims and a leg, like a liver and like a fetus are all human life. They are not however human beings in and of themselves.

How does birth transform the fetus? A c-section is a complietly diffrent process to a natural birth

And if I had said natural birth you'd be correct. I did not. I simply said birth. How birth happens, and a fetus undergoes the transformation into a human being can take place through both natural and artificial means. Just as how a fetus can be created through natural processes like sex and through interventions like artificial insemination.

A human fetus is a seperate organism to its mother, it is of the genus Homo Sapien and is alive.

Biology would disagree since a fetus doesn't exist independently. A human being, by definition, does. A fetus is part of the human body. When it becomes independent via birth, yes it is transformed into a separate human being. Prior to that it is not however. Anymore than sperm, prior to its merger with an egg, is a fetus, or a human being. You're lucky the rest of the world doesn't follow your unscientific and superstitious beliefs otherwise you'd be guilty of murder every time you masturbated or guilty of negligent homicide when you had inadvertant nocturnal emissions.

fetus is a human life.

Yes, like a sperm, like a liver. Like a leg. What it isn't is a human being. It is a fetus. You do know there's a reason the term exists right? Its describing a biological reality. A fetus and a child have always been separate entities.