I disagree (because I have a "universal life ethic" and believe that a mature society should see that all humans have an intrinsic right to life), but I found a pretty good summary of the pro-choice position via a Facebook comment to a Dennis Prager video on https://facebook.com/prageru:
"Another problem I had was the collating and commingling of value and rights. Fetuses have value - even aborted ones, for research - but they don't have rights. See, rights begin where another's ends. That's pretty much the definition. Well, being inside another person doesn't afford the parasite any rights - there is too much co-mingling. Thus, we grant the mother all the rights, which she can extend to the fetus (and sue for damages if it is harmed) or deny (and thus abort)."