Just want to add my experience, there is no theory behind it at all, no trying for one or the other but with my boys we were trying to fall pregnant and therefore DTD during the days i knew i'd be fertile.

With this little one i can not remember when we DTD to fall pregnant (before, during, after o'ing) but it was a total surprise and last week we found out we're having a little girl.

So for us it was the planning and thinking about it that produced our boys and the not planning and not even considering another bub that gave us a little girl