Actually there ARE people who want to see post-birth abortion legalized, potentially up to age 2.
There might be, but it's not a mainstream opinion, and is never going to become a 'thing'. So your use of it as an argument is specious.
A fetus is a human being that is growing, taking in nutrients, developing, moving, and has its own unique chemical makeup distinct from the parent.
These are characteristics of an organism.
If a fetus is alive, and it's human, that means it is a human being.
Amoebas are organisms, so is the bacteria that causes bubonic plague. Being an organism is not sufficient to qualify something as human.
A foetus is only alive because if it can use the support system of a woman's body, without that it can not survive. It might have the potential to become a human being, but at the point that it's a blob it can in no way be said to have rights that supersede those of the person it is attracted to.
As I said above, there is no law in either the UK or the US that says a living person can be compelled to use parts of their body to sustain or save the life of another.
Once again, I astonished that someone who claims to be a nurse can be so lacking in understanding of basic biology.