The Collaborative International Dictionary of English v.0.48:

pro-life \pro`-life"\, a.
   Same as antiabortion; -- used by those opposed to voluntary
   abortion, to emphasize their view of a fetus as already
   living, and to avoid the negative tone of a word beginning
   with "anti-".
   [PJC]

WordNet (r) 3.0 (2006):

pro-life
    adj 1: advocating full legal protection of embryos and fetuses
           (especially opposing the legalization of induced
           abortions) [ant: pro-choice]