The Collaborative International Dictionary
pro-lifer
pro-lifer \pro-lif"er\, n. One who is opposed to voluntary abortion; one who is pro-life, especially an activist in the campaign to make abortion illegal.
Wiktionary
pro-lifer
n. A person with pro-life views, or who advocates such policies
WordNet
pro-lifer
n. an advocate of full legal protection for embryos and fetuses; someone opposed to legalized induced abortion
Usage examples of "pro-lifer".
There would of course be some irreducible uncertainty: It may take hours or days after the sex act for conception to happen (a particular difficulty for pro-lifers who also wish to dally with Sun-sign astrology).