re: #131 Rustler

Morning after pills prevent implantation in the Uterine wall not fertilization.

from the PlanB package insert:
Emergency contraceptives are not effective if the woman is already pregnant. Plan B is
believed to act as an emergency contraceptive principally by preventing ovulation or fertilization
(by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by
altering the endometrium). It is not effective once the process of implantation has begun.

whole thing is here