Reply #126: Your planned parenthood link is exactly what we've been saying

[noamnety]

It "usually works by preventing fertilization of an egg." This is what we've been trying to tell you.

That's exactly what you said it couldn't do, hopefully now that you've read that link you can understand you were mistaken, that is the primary way that it works, preventing fertilization.

If that fails, yes, it prevents implantation, but as my lower link shows (the one to the doctor spock site), you are more likely to have an unimplanted fertilized egg without birth control than you are with an IUD.