[XBob]

391 - WRONG - "Contraceptive pills are designed to work by preventing the release of an ovum (until timed just right) via interruption in the leutinizing hormone cycle. Most also have a secondary (that means not the primary or main) effect to destabilize the uterine lining so that implantation fails or doesn't last when the menses is stimulated by withdrawal of the hormone 'extras'. "

You need to add 'some' in front of your comment. There are numbers of types of contraceptaive pills/methods, and a number of them work only by causing an implant failure, and one (I forget which one), held the largest market share a number years back - I don't know the current status) .

[hocndoc]

I don't know of any pills or methods that work "only by causing an implant failure." Even the IUD works mainly by irritating the uterine lining, increasing white cell counts, changing the pH and consistency of the lining and generally making it difficult for the sperm to make it to the oocyte.