Good point. We are sentient though, when does a fetus become sentient? Until that point it is not actually alive.
This is factually incorrect.
Even the egg cell and the sperm cell are alive by themselves.
But okay, thy are not a new human being.
But genetically speaking a fertilized egg cell is a living being, and it's human, so it's a living human being.
None the less, your question is valid i.m.o.
When should we consider this "person who not yet is" to be a person?
When does a foetus become a person?
I don't know.
At what point does a seed become a tree?
I don't know.
But i think we can all agree that abortion is too late when the foetus is more than 3 months into its development.
But, what if it is deformed or otherwise fatally unhealthy so that the new born will only have a short life full of suffering, or it will be a painful miscarriage?
Wouldn't it then be a "mercy killing" ?
Either way, the problem with abortion is people thinking lightly about it.
It should always be a difficult decision and for good reasons.