Missmuffet if calculating from the first day of your cycle, it does seem a bit early as you would have to have a very short cycle - have a play around with the Mumsnet due date calculator Perhaps you ovulated early?
My date has been brought forward a couple of days, I have fairly short cycles, but even so that would make mine only 23 days, which is short for even for me. Perhaps I ovulated early also? Hmm ....
Just did a quick google, and found this, which seems to be saying that calculating from your cycles is more reliable, except in some circumstances. So I'm wondering why they've amended the date on my notes? I'm confused now! Not keen on an earlier date if it means the chance I'll be induced is greater. Will ask the midwife next time I see her.
" How accurate is the ultrasound examination?
The earlier the ultrasound is done, the more accurate it is at estimating the baby's due date.
Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation. This is because the fetus is growing so quickly that there is a big difference in size from week to week. Also the fetus cannot bend and twist too much yet, so the length of the body is fairly constant.
However, the accuracy of the ultrasound examination is always dependent on the skill of the sonographer and the quality of the equipment.
The scan or my dates - which should I believe?
Usually the expected date of delivery (EDD or EDC) is calculated from your last menstrual period if the early dating scan calculates the EDD to be within 5 days of the EDD from your last menstrual period.
The EDD from the early dating scan is used if the last menstrual period is not known or is unreliable, or the dating scan differs from the last menstrual period dating by more than 5 days.
As the baby gets bigger, it starts to express its individual growth potential. The size of the baby correlates less and less with its age as time goes on. Utrasound examinations from 12 to 22 weeks are regarded as being within 10 days of accuracy (or up to 10 days earlier or 10 days later than the woman's calculated due date)."
Probably worth noting I have no idea how reliable that is! It's was just the first link I found that seemed to be talking about the right thing. It's Aussie, not that that should make any difference, I guess they use the same technology over there?
Link here
13+2 or perhaps 12+3! 