I hate to see bad information being passed around. It's called "early pregnancy factor" - a protein your body produces hours after fertilization occurs and it will show up on a blood test.
Pretty cool stuff to read about. If you feel like google-ing, there's a wikipedia page and a bunch of research articles on it. It was discovered back in the 70s. Makes me wonder why there hasn't been more research into this since and why its not more widely known.