Hi,
Despite being 35 weeks pregnant, I still can't seem to get my head around due dates, and cut-off for flying. Please help as I need to book a ticket within 24 hours for a quick (and final!) short-haul flight 
My due date is 18 January. So, I am currently in week 35 - I think! My question is when weeks start and end.... and in order to do this accurately for the airline, I need to count backwards from my due date.
Question is - on my EDD, will I have completed 39 or 40 weeks of pregnancy? i.e. is my EDD the day after 39+6 and at 40+0, or at the end of week 40, which technically speaking is surely 40+7. When is your actual due-date supposed to fall?
So, for example, if today I am 35+6, a week from today, will I be in my 36th week or pregnancy, or my 37th?
I know I should be able to work this out by now but in my pregnancy-fuddled brain I seem to be totally confused!