How do you know if your due date is accurate? (ultrasoud, multiple ultrasounds give same date, lmp, etc?)

Last cycle: If you have regular monthly cycles, and know your last cycle, this is a good standard to determine your due date. If you are unsure if your cycle, then you will be dated by an u/s. If the first u/s was performed in your first trimester (before 12 weeks), this will determine your due date. It will not change, regardless of other u/s obtained later, b/c due dates become more and more inaccurate.

Pregnancy dating: The best dating is an accurate last menstrual period date confirmed by an early ultrasound. But not many women have that. Second best is an early ultrasound dating. Remember a term pregnancy is 40 wks +/- 3 weeks. Your due date doesn't mean you will deliver on that date. It's just a means of knowing how pregnant you are.