I consider myself pro-life because I support the idea that human life begins prior to it scooting out from the vagina.
I think this is a much more complicated statement than you seem to think.
Defining is life is a contested task, both philosophically and biologically rather than open and shut case, after a few millenia we're not even close yet. (In fact the concept of life is likely incomplete and flawed, but I digress.) Take for example a cancerous tumour - it is clear that it is living but not in sense that your position wants. No one would regard cutting that out as an abortion.
What your position relies on is rather the religious concept of 'ensoulment', that element which gives personhood (according to christianity, at least). Although current views tend towards the moment of conception constituting this soul-giving historically there has been quite a lot of variation often with dates between a month and three months after conception being prevalent. (cf. Phillip K. Dick's 'The Prepersons' where abortion is considered legal until about 12 since the soul is not thought to be present until the ability to do algebra is demonstrable.)
The significance of this becomes apparent when we consider that criminalising abortion does not affect those christian women who are always going to carry a pregnancy to term (in the ordinary course of things) but rather a whole other bunch of women many/most of whom do not share this religious view of ensoulment.
That is is why the argument about 'potential' human persons (i.e. the unborn) attains its place. Unfortunately it is riddled with problematic reductio ab absurdum (see Reelya's comment, and also Monty Python's 'Every sperm [and egg] is sacred') since there is a whole developmental process which extends both before conception and after birth (P.K. Dick - although it should be noted that he wrote that story specifically as an anti-abortion comment on Roe vs. Wade).
While I'm totally fine with, and often even staunchly defend, the right of people to hold religious views that my bizarreness finds peculiar, that only extends so far as until it comes into contact with the right of others to peacefully conduct their own lives.* Hence I'm fine with Muslims believing it is blasphemy to portray their prophet up until they start killing people over it. And I'm fine with christians having strange procreative practices and values up until it comes into conflict with others who have different beliefs and practices.
To round out with a soundbite from an Australian senator from a few years ago in reference to a potential ministerial (=political) veto over use of RU486 (rather than being overseen by the Therapeutic Goods Administration): [edited]
"Keep your rosaries off our ovaries."
How hard can that be?
* Still gonna tell em they're wrong from time to time though.