For anyone interested in reading a detailed refutation of the claim that “personhood” (i.e. rights) begin at fertilization, I’d recommend two sources by Ari Armstrong and me:
(1) The essay “The Assault on Abortion Rights Undermines All Our Liberties,” just published in “The Objective Standard” : http://www.theobjectivestandard.com/issues/2011-winter/abortion-rights.asp
(2) A 2010 policy paper — “The ‘Personhood’ Movement Is Anti-Life: Why It Matters that Rights Begin at Birth, Not Conception” : http://www.seculargovernment.us/docs/a62.shtml
If you understand the nature of rights for what they are — moral principles required for survival and flourishing in human society, not arbitrary gifts from God — then rights can only apply to born infants, not to embryos or fetuses.
