Randy Alcorn has written a book called Why Prolife? which I highly recommend. He is currently offering it in a free pdf downloadable file at his website Eternal Perspectives Ministry.
I highly recommend everyone download and read this, regardless of your current beliefs. In Randy's own words:
Though I'm a Christian, I don't make many arguements from the Bible in this book. (I've done that elsewhere.) The case I present is grounded in medical science and reliable psychological studies. These sources should be as credible to any truth-respecting agnostic as they are to Christians. Indeed, many non-Christians oppose abortion.