I jumped a week forwards. Only did the naughty once that month cos i was away and then OH was working nights so i KNOW when we conceived..
and i was given 15th Nov as my due date which matched conception time. Had scans at 6, 8, 9, 10 weeks due to history and that matched my 15th Nov due date...
then went for scan at 11w and they said 12w! We'd jumped a whole week!
It was a private scan so MW dismissed it as rubbish and said that the consultants dates matched mine.. etc..
thought nothing of it, went to the 12w NHS can and i was STILL a week ahead of myself and LO measured 13 weeks.
So they adjusted my due date to the 8th and its stayed the same ever since!
I dunno what happened.. he just grew two weeks in a week.. luckily he hasnt done it again since