Not an ethical issue in the OT; maintaining population growth was a national priority. But cf. Jer. 20: 15–18. For Christian theologians the issue of when human personhood and immortalizability begins is contentious.
Citation for abortion
Citation styles are based on the Chicago Manual of Style, 15th Ed., and the MLA Style Manual, 2nd Ed..
MLA
"abortion." In A Dictionary of the Bible. Ed. W. R. F. Browning. Oxford Biblical Studies Online. Jun 19, 2013. <http://www.oxfordbiblicalcstudies.com/article/opr/t94/e17>.
Chicago
"abortion." In A Dictionary of the Bible. , edited by W. R. F. Browning. Oxford Biblical Studies Online, http://www.oxfordbiblicalcstudies.com/article/opr/t94/e17 (accessed Jun 19, 2013).