Embracing post-fertilisation methods of family planning: a call to action.

Family planning methods that act when administered after fertilisation would have substantial benefits: they could be used longer after sex than current emergency contraceptives, and potentially a woman could use them only on relatively rare occasions when her menstrual period is delayed. Although such methods would displease abortion opponents, they would likely be welcomed by many women. Research to develop post-fertilisation fertility control agents should be pursued.