Mine has changed a few times, I had myself due on the 27th based on LMP, I charted my cycles for 6 months with 4 or 5 at 25 days and the one before conception being 26 days.

At first I was put down as the 23rd of Oct, based on the early scan, then everything went to crap, and after many weeks my final EDD is now the 30th of October which I guess is giving us a bit of extra room with the growth scans atm