I would go by the early scan only because thats what most dr's/obbys are going to go on especially when your looking at being closer to term and if inductions/c-sections were getting discussed. From an obstetricians point of view they will take the medical facts (that the early scan gave you a EDD different to LMP) and use that not the date you tell them you DTD or O. I am sure your right about your dates and I know abdominal U/S is said not to be as accurate as a vaginal U/S so if you had both these done at your scan you probably would have dates almost a week apart anyway. But simple because of what the Obby would say I would go by the later date and that way when bub comes earlier it will be an added bonus. If you go over there date (by U/S EDD) then you will be going well over by your date. For me it would be a mind thing. Think the latest date because anything earlier is a bonus. But then thats me trying to trick my mind into not being disappointed if my date came and went. I was in this situation 2yrs ago and I went 4weeks before the Obby said I was due which was 2weeks before I thought I was due. My DD was well cooked despite being what they said was 36weeks (and 8lbs)