Hun I would stick to my guns on that one.

If you EDD is correct then you can say to the dr that the EDD they offered you would mean you Oed on the first day of your LMP, and you know your cycle well. I have told my MW that I want to have the latest EDD possible to reduce my chances of induction and she agreed as I advised her that I had been charting my cycle for 6 months before conception and I know that I Oed on day 17 and had a 12 day LP. She is happy to stick with my O related EDD considering it is only a few days after my early scan dates.

A scan at 18 weeks is not as accurate on dates as an early scan and early scans always say x weeks +/- 1 week on the report. You have every right to refuse to be induced. If they ask you to have daily monitoring then agree to that but do not agree to the induction.

They cant induce you if you dont show up on the day of induction anyway, so if they insist on iducing you on a specific date, then dont show.