I don't have any personal experience, but from what I've read I think it all depends on the amount of bd'ing you are doing.
I read a research study that looked at a few hundred women trying to conceive, they found in the average cycle there is a 40% chance of conception. Only 50% of those conceptions will go to full-term (25% chemical, 25% mc). This was only for women who were having regular sex.
So I think if you bd every other day or 3/week it shouldn't really make too much of a difference whether you are "ttc" or "ntnp". Maybe a few percent on either side of the 40%.
I don't know if it's true of course!