We've had this debate before.
Right - I forgot.
Basically:
1) If a fetus has a right to life then that right of life cannot be violated even as a means of restoring another right (autonomy, life etc). An action that does this is morally wrong.
But does this apply generally? We don't force people to donate life-saving organs or tissue - or even blood - and we don't force people to put themselves in peril to save others, so it seems it's not true in a general that we demand that others give up their autonomy or bodily security to save another life.
You say that you're considering a fetus a person, but it seems that you're demanding rights for the fetus that actual people don't enjoy.
My rationale:
There is no strong imperative to restore violated rights but there is to not violate already intact ones. For example, take life. There is not a strong onus to heal people who are dying but there is a strong onus not to kill people who are healthy. In a similar way we have a strong duty not to steal (i.e not violate rights of property), but a weaker duty to restore the property of victims of theft.
That seems like a wonky approach to me, but regardless... you think that a fetus - something that depends on a form of literal life support to live - is more akin to a healthy person than someone who's close to death? Why?
When a women is pregnant, her right of autonomy has already been violated (either out of her own actions, or action of others, i.e rape). Thus the culprit must be punished for that transgression.
A person can't violate their own autonomy. In most cases, the first thing that would violate that right is being refused an abortion.
However, she cannot use other's rights (namely a fetus' right of life) as a mere means to restore that autonomy. I cannot steal from someone else (violate their right of property) merely because someone stole from me (to restore my violated right of property).
Are you talking about legal or moral rights here?
Legally, it's clear that yoir interpretation is wrong: if my property is stolen and then sold to an unwitting third party, I can get my property back, even if the unwitting third party can't recover the loss from the thief.
2) A fetus has a right to life
My rationale:
Essentially my definition of person-hood is eventual rationality. Sentience is too wide (think animals etc) rationality alone is too narrow (i.e we exclude comatose patients, etc) and thus eventual rationality I think is an arguable definition.
"Arguable" is an understatement... but it seems like you would agree that a fetus has
no more rights than a person does; correct?
3) Abortion does violate a fetus's right of life as a means of restoring autonomy. (this just follows from (1) and (2) )
Conclusion: Therefore Abortion is morally wrong.
Except you haven't established that the fetus's "right of life" supersedes the right of the pregnant person to autonomy and bodily security. All you did was decree this without justifying it.
In general, autonomy and bodily security always win out over the right to life: for instance, people aren't compelled to risk their lives or provide organs and tissue for others. This right even continues after death: if your wish while alive is that your organs not be donated, then when you die, your organs are buried or cremated regardless of how many lives they would have saved.