Anyone any experience of the accuracy of dating scans? My pregnancy wasn't planned and as a result was never too sure of my dates as wasn't sure about my last period. People are now telling me how huge I am for 7 months and as a result i'm worried that I could be further on than the dating scan put me at. Is there any chance at all it could be out by a month or two or could it only really be out by a week or a few days?