enigo, i asked the same thing. i don't have a child to complicate things, but i wake up often. someone recommended taking it every time i wake up, and see how they compare. over time a pattern should emerge that will help you be sure.
i know that's probably even worse, b/c of the beeping, but i definitely think as you're awake, your temp will rise. maybe if the first wake time is always at least after 3 hrs of sleep, it would be easiest and most consistent?
if you turn over the thermometer, there's a little hole you can see (on all the ones i've used). if you plug that firmly w/ your thumb while you temp, the beeping is much quieter. i also push the button after the first beep, then push it again to reveal the temp, since digis save the last temp.
me+him for 15 yrs, welcomed our little one march 25th, 2010.