Mmm... I didn't bother with the early dating scan, as I knew exactly when I ovulated, and the doc told me that this was a more accurate way to determine the *Estimated* Due Date than the scan. Plus I found that having a particular date stuck in my head for my first birth to be a negative thing - everyone placed so much emphasis on THE date, even highlighting it in their calendar etc, etc.
I ended up going into labour at 38 weeks (2 weeks before EDD) and learnt quickly that the baby has little regard for estimated dates or external hospital agendas.
In the end - only the baby can determine the true due date, and it is not they that get it wrong, but the system. I read somewhere that only 5% of babies come on their actual due date!!
When people ask me the due date of this pregnancy, I tell them "The baby is due when it comes..." "Only time will tell...." etc etc. If less emphasis was paid to EDD's, we would not have such high intervention rates - artificial inductions for no valid reason other than being past the EDD, distressed babies as a result, emergency c/sections etc.

Anyways, thats the end of my spiel. At the end of the day - EDD is just a guide. I think being fully prepared for labour from 36 weeks is advisable just to be on the safe side.

Wishing you a good labour and birth!!

XX