Why 40 weeks?

[emkana]

What is the reason that the length of pregnancy is defined as 40 weeks? I know so many people who were "late" (myself included) and so few who were "early". So who decided that 40 weeks was the "correct" length? Anybody know?

yeah it rubbish emkana
5% of babies arrive on their due date
of the rest:
30% before
70% after
in France (iirc) the dd is a week later

Indeed.... the average gestational age is 41 weeks....

The birth centre told me that the average period of gestation for caucasian women is 41 weeks so the French have got it right. Makes me mad tht so many women are induced who have barely got to this stage!

I always heard that women were actually pregnant for 10 lunar months, hence the 40 weeks.

Oh, and my water did actually break on my due date so ds was just following orders...

I'm in France, and the way they calculate due dates is nothing to do with weeks at all! In fact they take the estimated conception date (using a scan not your last period) and count nine months from that. So if your pregnancy includes February it's supposed to be shorter . I'm due on the 24th of December using the 40 weeks count, but my official due date in France is January 2nd.

The 40 weeks is also calculated using a 28 day cycle.

here's my advice:
if you're asked for the date of your last period say you don;t know/can't remember
then they will date you according to your dating scan. much more accurate

i agree - a group of us met to discuss this -of 10 1 was early one on date ...8 late! silly - should be 41 weeks!

I'm so in agreement with this, especially as I am 40+6 and feeling like I'm in limbo. Even though I knew first babies are often late and tried not to focus too much on my due date, you can't help feeling responsible that the baby is "late" and that everybody around you is waiting and expecting.

On a practical level, I am eating into my maternity leave ( I know it's nice to have this time to yourself, but...), and the later she is, the younger she will be when I have to go back to work. If they gave you a due date of 41 weeks, however many weeks before you decided to finish work (in my case, 3 weeks before due date), you would finish a week later, and you wouldn't have this unreal anticipation feeling for a week.

Anyway, if the average is 41 weeks, then maybe tomorrow....keep your fingers crossed for me! And I've got everything crossed for you, emkana....