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Due Dates: Is 40 weeks a myth??

(19 Posts)
JRWREN2110 Tue 23-Jun-15 09:51:33

So at 39+6 I am getting utterly fed up and I got myself wondering about due dates and how is it that we all get fixated on this particular date when most of the research shows that the majority of women don't have their babies on that date at all!

According to this article (see below) if you are a first time mum your due date can be calculated by counting 3 months back from you LMP and adding 15 days (and this date will be your EDD for the following year), for second time mums it 3 months back from your LMP and add 10 days. PLUS, if you have a shorter cycle e.g. 24 days you will deliver before this new EDD, and a longer cycle e.g. after this new EDD.

So, what is your new EDD according to this theory?? What do you think?

My new EDD is 2nd July (my old one being tomorrow 24/05/15)...bit of a difference, I think she will come around then too as I had a standard 28 day cycle. I feel a little more relaxed about when my baby arrives now, as my due date is tomorrow and I have no BH, no show, NADA...

Athenaviolet Tue 23-Jun-15 10:01:03

Yes, edd is a myth!

Different countries use different methods of calculation.

Babies are 'due' from 37-42 weeks.

'Overdue' is 42+1 not 40+1.

So many unecessary inductions are carried out because of this!

I refused to provide my lmp date with dc1 because that would have put my pregnancy at 46 weeks. I have long cycles but they just don't take that into consideration!

Skiptonlass Tue 23-Jun-15 10:02:43

Not so much a myth as a slightly fudged best guess. smile

Some countries use 41 weeks... It's almost impossible to predict on an individual level. On a population level you have the distribution curve of date of delivery vs gestation time but on an individual level it's more to do with individual factors. The prevailing theory now is that you go into labour when your metabolism can no longer meet the energy needs of the foetus. Fascinating stuff.

NickyEds Tue 23-Jun-15 10:26:29

I think around 5% of babies arrive on their due date so by no means an exact science! I vaguely remember someone on here saying that in France you get a "due month" rather than a due day which seems more sensible.
Skiptonlass I'm 37 weeks and definitely feeling like my metabolism is not meeting the energy needs of my baby! Or my 18 month old. Or me! You should see me trying to get out of a low chair!

caffiene99 Tue 23-Jun-15 11:02:51

Nicky's right - recent research supports the approach in France. Due dates can vary depending on the woman and the pregnancy. 40 weeks isn't accurate for everyone.

During my first pregnancy the midwives told me that, in their experience, about 90% of first babies are 'late'.

Having said that - my first baby was born 20 mins before his expected due date.

My sister and I were both born on our exact expected due dates - there seems to be some evidence that your due date may be related to when you were born yourself (IYSWIM)

MissTwister Tue 23-Jun-15 11:17:55

I thought first babies were no more likely to be late or early than any other. The head of MW as my classes said they're just as likely to come anytime during week 38-42.

ohhello Tue 23-Jun-15 11:19:43

It's 37-42 weeks, usually not longer with first pregnancies than subsequent. The rest is down to nature!

ButtonMoon88 Tue 23-Jun-15 11:23:46

I was given two dates with my DC1, 21st Jan and 2nd Feb. She ended up arriving 23rd Jan and was 54cm!! She was obviously very ready to come, I don't know if I was 37,38 or even 40 weeks by the time she was born, but I do know she wanted out!!

foxmitten Tue 23-Jun-15 11:29:09

I was born a week after my due date, all of my children were before theirs.

Interestingly though my siblings and I got later each time (my older sibling was on due date, then me a week after mine, then younger sibling over two weeks after) then my children were earlier every time (first 1 day before due date, second 3 days before, third ten days before).

Anecdotal evidence but interesting nonetheless.

Roseybee10 Tue 23-Jun-15 11:39:13

I think it's so silly to have a fixed due date. I think all women gestate for different lengths of time tbh.

I'm one of the few who naturally seems to be around 40 weeks. Dd 1 went into labour at 40+2 and she was born at 40+4.
Dd2 I went into labour at 39+5 and born at 39+6.

Skiptonlass Tue 23-Jun-15 13:23:22

Nicky, I feel your pain. I'm only 23 weeks and I need a bloody crane to get off low sofas smile

BlueKarou Tue 23-Jun-15 13:40:31

I just assumed that 40 weeks took you to the average gestation period, and that it was more like a bell curve (but slightly skewed, as obviously premature babies are a thing, but inductions should stop any babies going past 42ish)

DoJo Tue 23-Jun-15 13:47:09

In some countries you are given a 'due month' which gives you a more realistic expectation about when your baby will come which seems much more sensible.

AmberLav Tue 23-Jun-15 14:12:10

I was one day early, my babies have been 6 and 10 days late...

I have a friend who only carries for 36 weeks, and her babies come out small but perfect... she's tiny too though...

ButtonMoon88 Tue 23-Jun-15 14:15:00

DoJo- that's interesting, a due month?! it would drive me mad thinking that my child could be born any point within a 28-31 day window but actually it is much more realistic!!

Youmakemydreams Tue 23-Jun-15 14:29:02

All 3 of mine were earlier than my due date. 2,3 and 2 weeks.
With baby number 2 I gave myself a due month. I told myself he'd be here in May. I didn't want to fixate on a date as ds had been early I dufnt want to bank on that so just said May. He came on 29th April hmm when I had ds2 even the day before I was convinced I'd go all the way this time but he made an early appearance too.

CarrotPuff Tue 23-Jun-15 15:15:08

That's why they don't call it a due date, it's an estimated delivery date. Yes, it is an average, and there are women who cook their children longer or shorter than others, but they can't really tailor it to everyone, can they? They need some kind of "base" to work from. It's us who actually get fixated on these dates as an absolute due date, they do say it's an estimate and your baby can be born any time from 37 weeks onwards.

PearTree201 Wed 24-Jun-15 13:19:13

When pregnant with DC1 I was terrified I'd go over my due date after hearing horror stories about how awful it was to be overdue.

My waters broke out the blue 2wks and 2 days early at home. Would much rather that and hoping DC2 will be the same!

WinterOfOurDiscountTents15 Wed 24-Jun-15 13:22:24

It's not a "myth" of course. It's an estimate. It's never intended to be anything else. Just because people get overly hung up on a particular date doesn't mean there is anything wrong with the estimating method.

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