But it turns out, at least when it comes to Plan B, there is now fairly definitive research that shows the only way it works is by preventing ovulation, and therefore, fertilization.
"We've learned a lot about how these drugs work," says Diana Blithe, a biochemist and contraceptive researcher at the National Institute of Child Health and Human Development. "I think it's time to revise our speculations about how things might work in view of data that show how things do work."
For example, says Blithe, a study published just last year led the International Federation of Gynecology and Obstetrics to declare that Plan B does not inhibit implantation. And some abortion opponents in the medical community are beginning to accept that conclusion.