Well my periods are usually between the 9-11th of each month and it was pretty right on without me even telling them. Cause initially I told them my LMP was May 9th but to my mistake I was much more pregnant than that... I suppose I was spotting around that time. Then I remember waiting all May for my period and it never coming. I was going through a lot that month. Come June I was much more settled and life was less chaotic and it hit me... so my supposed due date is 1/14/11 which means I conceived around 4/23 which makes perfect sense. Technology these days.
Hi, okay well they would still base your estimated due date the same way. The first telling 'sign' they usually go by is the date of the first day of your last menstrual period and they will count 40wks forward from that day, or if you happen to know the actual date inwhich you concieved they would count 38wks from that date. The most 'accurate' way of telling your dd (so I've been told) is by your earliest ultrasound.
Hope this helps some, take care.
Do you mean you did not find out you were pregnant until you were about 13wks pregnant, and you are wondering if because you didn't find out until later in the pregnancy if the due date you've been given is accurate?
If by finding out at that time, if the calculation of the due date can be really off. I don't really know how to word it... haha.
Im confused on what your question is exactly..