My friend Razib, writing as David Hume at the Secular Right blog, has looked at the data on international attitudes towards abortion and made some intriguing observations, notably:

1) It is clear that religion correlate with opposition to abortion in the vast majority of nations.

2) But, the attitudes of religious people and non-religious people track each other so that the irreligious in nation X may oppose abortion much more than the religious in nation Y.

That second point is really quite thought-provoking. It certainly underscores the moral subjectivity of abortion relative to issues like murder which have a clear and universal moral concensus.

Related: my earlier post on the need to move beyond simplistic pro-choice/pro-life axes for the abortion debate, and also ongoing discussion of abortion at Talk Islam.