I know that the doctors go by the date of your last period, but isn't there a time when they can change when your due. When do they get to be more accurate and is it ususally earlier or later than 1st determined
My dr told me that the first u/s you have is usually the most accurate at predicting your due date. Who knows though since I am at 33 weeks, yet I am measuring at 34, and so they are telling me I only have 3 weeks to go till I am term. So even though your u/s may give you a pretty good idea, the further you get along, things may change enough for them to change dates, like your measurments. Hope that helped!
Your due date is an estimate at all times! The reason they say by your ultra sound is because they measure the baby's bones and head and have an pretty close estimate by the baby's bone size. From what i hear your EDD is give or take a week! but your baby will come when he or she is ready not you, that's how baby's work
I've heard that the most accurate due date is taken from a scan around 12 weeks. In the UK they actually refer to this scan as 'a dating scan'. Apparently before or after this time the dating is less accurate. I was originally given a due date based on my last period and then this was checked at the dating scan. In my case they reckoned that the measurements from the scan were within a week of the original date so they didn't change it. Obviously it's still only an estimate though....