I had always heard that too but myself, and MANY of my friends, had a much harder time getting pregnant with our second children. That theory is out the window. I'm not answering your question but I just wanted to recommend buying an ovulation microscope. They sell them at any pharmacy but they are $40. You can get them much cheaper online or on ebay. I used one to conceive our second child. It worked great!!!! Every morning (as soon as you get out of bed) you put saliva, from under your tounge, onto the glass. Let it dry and then look at the pattern under the microscope. If just bubbles, you are not ovulating. If you see some ferning pattern, you are approaching ovulation. Once you see tons of ferning, you are fertile. Just after you ovulate, it will go back to bubbles. One thing it took me months to figure out is that you have to use a huge glob of saliva for it to work properly. The instructions don't say this. Estrogen levels in your saliva cause the ferning pattern. Lastly, I knew I was pregnant long before a pregnancy test read positive. The day after I ovulated, I had bubbles again but 6 days later, it was ferning again (because implantation had occurred and estrogen levels were rising again). It was pretty neat and I highly recommend using one. It was pretty much effortless.