I get asked it a lot and I guess you, my loyal blog readers, should hear some more about it.
I am now coming up to 21 weeks pregnant. That is pretty much set though I'm measuring 1cm in front of that "guideline" by fundal height, so who knows what that means. But in terms of due date:
"Recent research offers a more accurate method of approximating gestational length. In 1990 Mittendorf et Al. undertook a study to calculate the average length of uncomplicated human pregnancy. They found that for first time mothers (nulliparas) pregnancy lasted an average of 288 days (41 weeks 1 day). For multiparas, mothers who had previously given birth, the average gestational length was 283 days or 40 weeks 3 days." Source
So 41 weeks and 1 day puts my due date at 25/03/2010 rather than 17/03/2010. Now for me, it matters not when bub arrives - I am comfortable knowing that sometime before Ostara next year, we'll be a family of 3. Which I what I'm telling people - either that bub is due in March sometime, or else "before Ostara/Easter".
What is amusing is if I tell people I'm 21 weeks, they'll go "ahuh", like it means something to them. If I say "5 months", then the assumption is that I have 4 left to go. If I say "March" invariably people go "wow you're big/small for that!", like they have any idea of what I should be now.
By the way I've updated my 101 in 1001 days list and need to get my bum into gear as it's now less than 2 years to go!