But that's the point - Tan's asking if women are so out of touch with their bodies that a sonographer is more of an expert on when they're due than the actual woman in question - and it seems that the answer is - sometimes they are that out of touch!

With both I've had the NT and morphology scan. With my first, I had no idea that cycle lengths could mean that ovulation happened at different times and so on - I'd always been textbook 28 days so I never thought much about it...before pregnancy I knew nothing about my body, so it doesn't surprise me that women aren't familiar with their bodies, cycles, symptoms. I had no clue. I only got into the Family Birthing Centre for a waterbirth because all the OBs were booked out! And I thought that was bad luck! Someone sure was looking out for me...

I imagine Tan, that your being confident about your dates and informed, might have been less usual than we'd hope. I'd love to see a little more education in high schools during their student development days - or was I just not paying attention (feasible option)?