Unborn people are unique because they are entirely dependent upon a mother to survive in a way that cannot be replaced.
The human right to life is not absolute, at least under current law: a person who literally requires your body’s metabolical processes to survive is not entitled to that, and so we have decided the provider has the choice to cease providing it at anytime, with the stipulation that at the time the decision is made, they cannot choose mechanisms to end it which unnecessarily harm the recipient.