In my doula bag, I have a dilation chart made of soft foam. One piece of foam with a circle cut for centimeters 1-10. It's slightly stretchy, which is a lot more accurate than those stupid plastic charts the ladies are so often shown in their childbirth ed classes.
As my client progresses, if she's checked, I'll show her where she's at. I also use the chart as an indicator of how subjective the measurements can be.
As for those docs that can measure 2 3/4 cm, good heavens!!!! How full of themselves can they possibly be?!?!?! (And it leads me to wonder, if it's a man, what he tells the ladies he's intimate with about his .... ahem ... endowment!
I also remind my clients that sometimes dilation means nothing. We're all familiar with the 4 cm. "transition". And how you can have someone who goes from 3-10 quickly, but the lady in the next room decides to park at 8 cm. for hours and hours. Those numbers are only good to a point.
Penny Simkin, childbirth educator and doula extraordinaire, likes to predict the vag exam results by watching emotional signposts instead. She finds herself to be fairly accurate.
And once that mama's water is broken, it's not like you want to stick your fingers in there that often anyway ... it really raises your chances for infection. ick!