I think it is possible to be both pro-life and pro-choice. As in, while you personally have beliefs which would prohibit an abortion under all but extreme circumstances, you can support the choice being available for women who do not feel that way -- or perhaps did, until it happened to them. This could come, for instance, because you realise that whether or not you are pro-choice, some women will feel they are in a situation where abortion is their best option, and if the choice of a safe, legal abortion isn't available, then greater harm may result.
This is the distinction between "pro-life" and "anti-choice", if you see what I mean.