How accurate are dating scans at predicting Due Date?

Just curious to hear people's experiences as to how accurate the EDD you were given at your scans have been....
I had a dating scan at 6w5D which said my bub would arrive ON it's due date (1/1/2010)... What are the chances of this? I hear the earlier the scan, the more accurate it is but I want real life examples please!

I can't remember what my dating scan said with DD, who arrived at 38 weeks.

Thanks Lovelies!

I think that when it comes to dates you need to keep in mind that it is an *estimated* due date. Your baby is just as likely to arrive 10 days before or 10 days after its EDD.
Full term is usually anywhere between 38 and 42 weeks.
The good news is that all babies are born on their birthday :)

Both the dating scans for my boys were out by a week.

Even early scans aren't always accurate. I think this is more because not every woman has a 40week pregnancy. For some women there baby is just as baked at 37weeks as someone who is 42weeks pregnant. Without inductions may women would even go 43-44weeks pregnant. With my last DD my early scan at 7weeks gave me a EDD of 15th May. She arrived spontaneously 19/4 at 36+3 looking not the slightest bit early (no vernix, fat etc) and weighing 8lbs. I would offer early scans especially when you don't know your dates but when looking at baby's actual birth date to the early scan there is often weeks difference. I think they come when they come some earlier some later.

between 4 and 10 weeks the accuracy is only a day or two out at most after about 12 weeks it can be out by up to a week. I was told this by my sonographer 2 weeks ago coz my bub was measuring a week and a half ahead of schedule

The scans really assess the conception date rather than the arrival date as the baby can be born either side of the "due date" as others have said.

I know when both of my girls were conceived and worked out the "due date" from there - the scans showed a "due date" only one day out from our dates so they were pretty much spot on for working out conception dates.

DD1 was "due" on Feb 26th but arrived 15 days earlier on Feb 11th. DD2 was "due" Feb 22nd and arrived on the 19th.

It really is hit and miss...its just an estimate as others have said....ive been 'prepared' since about 37 weeks....and here i am, 40 weeks today and no sign of baby.....dont take it as gospel, bubs could come 10-14 days after your EDD......thats all it is...is a estimated due date...

Good luck !!!

My dating scan with this bub at 8 weeks was really inaccurate, it gave me an EDD of 28/8/09 when by my dates I should have been due around 22/8/09. Looking at the scan and where the sonographer took the measurements you can see he didn't include the baby's head in the measurements :o. My 12 weeks u/s gave me an EDD of the 21/8/09 and my 20 week u/s gave me an EDD of 20/8/09, so my later scans seem much more accurate.

I think I just got a dodgy sonographer the first time around LOL!

With my dd i had a scan at 6w1d and it dated her as 6w1d. By the time we got to 19wk scan she measured 1wk ahead. My waters spontaneuos ruptured 1 calender month before her due date. so 4wk3days early.

She weighed nearly 7pds at birth but she also got jaundice (more common in both preterm and induced babies/i ended up being induced) and feeding issues not uncommon for a preterm baby. She remained about a month 'behind' in her milestones up until 7mths or so where she caught up.

I didn't have an ultrsound until 12wks this baby and it has consistently measured 4-7 days a head in each ultrasound. Signs are that it will be an early baby (1/2way engaged, some mucus plug loss etc).

My EDD via my LMP is at 25/09/09...had my first scan at 11wks, gave me a EDD of 18/09/09...had my NT scan 2 weeks later, had my due date at 22/09/09, and my 18-22 wk scan, done at 20 wks, had me at 23/09/09....so I can safely say that my bubs is due anytime between the 18th and 25th of Sept....I usually split the difference and say the 22nd, but with my last 2 bubs, they were both post dates (my youngest being induced at 41wk + 3) so Im tipping I could go into October!

I got told by my OB that scans done from about 10 wks onwards will give you an accurate due date, but yeah, 10 days either side of that is pretty much the norm. :D

DD2 dating scan said 21st October...then 20 weeks scan said 23rd Oct...she came 26th october...5 days over due

Thanks Ladies...
ANyone else care to share their experience...I am getting that hardly anyone came within a day or 2 of their first scan (6 - 10 w)...?

Probably my DD (Baby no.1) was the most inaccurate...
an 8 week scan put my EDD at 1st March, but from about 22-24 weeks she measured 2 weeks further along (also not very accurate I know) - She arrived on 3rd March very close to her EDD but she was brown, wrinkled and peeling, she had the longest nails & all the mids commented on how 'over-cooked' she was!
DS1 arrived 2 weeks past his EDD (which was assesed as best as I could recall my LNMP) and he was in much better condition than her; DS2 was 10 days past EDD and also looked fine.
This time around I have a fairly good idea of when I conceived, that date, plus my LNMP, plus a 8 week scan all put my EDD within about 5 days - I think it will be really interesting to see when bub comes & how she is when gets here!(we are going with my LNMP date for 14th July, the scan says 16th I think)
Oh and I'm measuring 2-3 weeks further along this time, too!

Yeah, babies come when they are ready (sadly, not when we are! :lol:)

Mmm... I didn't bother with the early dating scan, as I knew exactly when I ovulated, and the doc told me that this was a more accurate way to determine the *Estimated* Due Date than the scan. Plus I found that having a particular date stuck in my head for my first birth to be a negative thing - everyone placed so much emphasis on THE date, even highlighting it in their calendar etc, etc.
I ended up going into labour at 38 weeks (2 weeks before EDD) and learnt quickly that the baby has little regard for estimated dates or external hospital agendas.
In the end - only the baby can determine the true due date, and it is not they that get it wrong, but the system. I read somewhere that only 5% of babies come on their actual due date!!
When people ask me the due date of this pregnancy, I tell them "The baby is due when it comes..." "Only time will tell...." etc etc. If less emphasis was paid to EDD's, we would not have such high intervention rates - artificial inductions for no valid reason other than being past the EDD, distressed babies as a result, emergency c/sections etc.

Anyways, thats the end of my spiel. At the end of the day - EDD is just a guide. I think being fully prepared for labour from 36 weeks is advisable just to be on the safe side.

Wishing you a good labour and birth!!

XX

First and foremostely, I agree that an EDD is definitely an estimate and nobody - particularly medical experts - should get toooo hung up on the date.

With DS, my earliest scan was around 5w4d (from memory anyway, it was before 6w whatever the case), and they gave his EDD as 19 March 08. My next scan at 12w3d gave the 16 March 08 as his EDD. My Ob always went by the first scan. But guess which day DS was born ... 16 March 08.

Andie