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Pregnancy

Talk about every stage of pregnancy, from early symptoms to preparing for birth.

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Original poster

Has anybody else had this problem with dating scans? I feel like I'm the only one :(

38 replies

BabydueAugust · 31/03/2011 11:57

Here it goes...
My lmp was 30th Oct 2010,However i NEVER have the perfect 28 day cycle,None of this came to mind when i visited the doctor he said i would be 5 weeks pregnant on that day based on a 28 day cycle,As it came closer to my dating scan i was nervous...Dating scan put me at 11 weeks 4 days pregnant as I worked out the dates on due dates calculators on here it puts me at a due date of Aug 6th & the hospitals are putting me at Aug 5th...I know the date of conception so these days could not possibly be correct I'm sure that they are dating me 1 week ahead of what I actually am & baby wont come along until AUg 14th...I'm going to my doc tomorrow to discuss this and see what she says? Has anybody else had this problem with dating scans been 1 weeks ahead of what you actually are in pregnancy? Or is it all just in my mind..

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midori1999 · 31/03/2011 12:12

Unless you know for sure when you actually ovulated and concieved (which even if you were using OPK's you might not know) then your dates by the scan may actually be right. Not everyone ovulates in the middle of their cycle or 14 days before their period starts.

That said, scans can be out by up to about 5 days quite easily. My early scans showed I was a week behind what my dates made me, which would have meant I had concieved the day I got my BFP on cycle day 21. Later scans have shown I am five days ahead of what my dates would have made me, which I am more inclined to agree with due to when I got my BFP and the size of the baby.

A due date is only estimated, baby could arrive between week 37 and 42, so I wouldn't worry too much.

KnitterNotTwitter · 31/03/2011 12:17

you don't actually know the date of conception - you know the date of sex! It then takes sperm at least 24 hrs to travel up to the egg, maybe longer.... Development then progresses slowly until the egg implants....

That said dating scans aren't an exact science. My calculated due date is the 17th of Oct while the hospital are predicting 21 Oct...

As midori says in the end it'll be your baby's decision and not anyones calculation that determines when you're baby puts in an appearance... everything else is just educated guess work!

Congratulations BTW - and Good luck!

Original poster

BabydueAugust · 31/03/2011 12:19

Thanks for your replies,So even though my dates are showing the same and not changing any due dates it could still actually be wrong? I'm just going to wait it out & see when little lady decides to make her apperance :)

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piprabbit · 31/03/2011 12:22

My DS is an IVF baby. I know exactly when he was conceived and the progress of the cell dividing and forming into a blastocyst for return to my uterus 5 days later.

My dating scans put me over a week ahead of when I knew DS was due. The hospital refused point blank to change their dates.

So, no, I don't have a lot of faith in scans for getting dates right.

KnitterNotTwitter · 31/03/2011 12:23

Yep!

Also worth mentioning that they thought my DS was going to be early because he was big - it's very easy for them to assume that big = cooked. What they can't measure is actual developmetn progress so they use size as a proxy measure.

Plus if you and/or your DP are petite then it's likely that your DC will be smaller and the reverse if you're giants!

Again - size isn't necessarily a measure of developmental progress.

paddypoopants · 31/03/2011 12:35

My dating scan put me at nearly a week ahead. I knew that couldn't be right as we only had sex once as DH had been away unless it was an immaculate conception.They stuck to the edd from the dating scan despite my protestations. They wanted to induce me at 41 weeks and I had to endure a really painful sweep at 40 weeks (which was really 39 weeks). My waters broke on MY edd.
My sil has been given an edd a week ahead of where she thought she was and she's all excited at being a week ahead - but it won't be much fun if she ends up with an induction when she could have another week to see if it happens by itself.

saldoozer · 31/03/2011 12:36

Based on my LMP and scans i concieved on a day when DP was in another country (and had been for about a week) as we know my BFP was the result of his return 2 days later I know that the due date is an estimate and based more on cycle length. I have no idea when I ovulated as i had stopped taking the mini pill around the time of the LMP.

VivClicquot · 31/03/2011 12:38

As everyone has indicated already, there is a reason why it's called EDD - ie ESTIMATED due date. The scans give you a due date based on the size of the embryo - which may be developing faster or smaller than the average, or may be an indicator that conception took place a couple of days after sex, or you ovulated earlier/later than you thought. Unless your dates are wildly out - ie by weeks - then it's not something I would get overly hung up about.

Original poster

BabydueAugust · 31/03/2011 12:39

I've heard alot of people have been induced due to being overdue by hospital scan dates...I think I'll speak with my doc tomorrow & see what she says about it,pleased i'm not alone although a lot of people said my dates seem to be right,Who knows! Guess its a waiting game even though i'm sure she will arrive on 14th Aug and not the 5th,Makes me wonder how given a EDD of the 5th and online calculators say the 6th? I know it only 1 day but..

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MrsTittleMouse · 31/03/2011 12:50

I've had this too - it's easy to know when I conceived because I needed fertility treatment both times. But my babies are big, and I've always been told that I was further along.

Original poster

BabydueAugust · 31/03/2011 12:52

It really does make you wonder how accurate these scans are! I'm shocked to how many other people have had this

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VivClicquot · 31/03/2011 13:02

The scans can only ever give you an ESTIMATED date, based on years and years of research over how quickly the average foetus grows. As we know, all babies are different and may grow faster or slower than the average. So a scan can NEVER be 100% accurate, but is as accurate as it possibly can be, given all available data.

Looking more long term, remember that only 5% of babies are born on their due date, because again, a whole host of factors contribute to when women go into labour. One such factor is family history - if your mother has a history of being overdue or early, the chances are you will too.

thefurryone · 31/03/2011 13:05

Just to buck the trend my dating scan actually put me at a date that pretty much fits in with date of sex that led to conception even allowing for the time it took for sperm to meet egg! I still have absolutely no faith in the baby arriving on my EDD though I would say that an margin of error should be expected on any scan, it is not an exact science by any means.

However, when the time comes there is absolutely no reason for you to go through a sweep or an induction if you don't want to or you feel it is not necessary. The hospital is obliged to over you monitoring from which you can make a judgement of when to induce if necessary. These are the NICE guidelines on induction of labour www.nice.org.uk/nicemedia/live/12012/41255/41255.pdf

MrsTittleMouse · 31/03/2011 13:14

I was about to post that anyone who agreed with their EDD wouldn't post on this thread, but you've just proved me wrong. :)

The trouble is that there are a lot of MWs and OBs out there who do put a lot of importance on the EDD, especially if the baby is "overdue". I have known a couple of other women (not just me) who just haven't been believed that the date must be wrong (and by a week or more, not just a day or two). It's really galling to be told that you must be wrong, especially when it's your own body!

KnitterNotTwitter · 31/03/2011 13:15

I have a lovely friend who when she went for her 12 week scan they said - oops - you're 16 weeks not 12... and it's Twins

Original poster

BabydueAugust · 31/03/2011 13:20

I know when i went for my 20 week scan & found out i am expecting a little girl :) I was 19 weeks 4 days (exactly the same amount of weeks and days as my dating scan) & midwife said she "we arent going to change any dates" however on my scan report she pointed out that on the scale it should always be in the middle & 1 of mine was at the end she did say not to worry! But not quite sure what it actually was or meant

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KnitterNotTwitter · 31/03/2011 13:27

Just means it's bigger than average if the slider is to the right and smaller than average if it's to the left - doesn't mean your dates are wrong.

there are other factors that will cause bigger (diabetes) or smaller (smoking) babies - sorry forgot to mention them earlier...

notasausage · 31/03/2011 13:27

I started at 4th of September based on my last period. 8 week scan put me at 2nd Sept and 12 week at 29th Aug. Same with my last pregnancy and DD was 10 days "late" according to the dating scan. Babies rarely come on their due date. Might be easier to plan for your dating scan date but expect it to be nearer you lmp date. Doesn't really matter otherwise. Don't get too tied up in the dates.

BarbieLovesKen · 31/03/2011 13:29

I have an exact 28 day cycle and could time my periods.

From LMP, I am due on the 1st June.

From 2 dating scans I am due the 28th of May.

I've no idea when I ovulated to be honest but remember remarking it was wonderful that I was pregnant because I was pretty sure we had sex on the "wrong" day (ie. not around day 14 of cycle - cant remember what day now, if Im honest).

The consultant didnt change my due date - its still the 1st June, which actually annoys me as Im confused. I know its only 6 days but a when your pregnant, a week is a long time and I'd prefer some clarity as since hearing the 28th May twice it has me pondering..

You have my sympatise.

Original poster

BabydueAugust · 31/03/2011 13:32

So if baby is bigger than normal what could this mean? I'm quite tall but i'm thin..not sure if this would make any difference towards the growth of the baby.

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naturalbaby · 31/03/2011 13:41

all 3 of mine had the dates moved forward by up to a week. with ds2 and ds3 i knew the date of conception so was convinced the scan was wrong, all 3 came pretty much on their due date from the dating scan. so in my eyes they were a few days early and covered in loads of vernix which midwives commented on so that confirmed what i thought. i'm also really tall and had 8lb 13 baby, 8lb 2 and 8lb5. i think that's also why the dates were moved forward a bit - i grow big babies!

i didn't need to but would have stuck to my convictions and refused induction if it came to it. i discussed it with my midwife first time round and she said i could have scans to monitor the placenta if i went over the due date and didn't want to be induced. so long as baby and placenta and mum are fine you should be allowed to carry on!

architien · 31/03/2011 13:42

Let's look at the facts:

Ok so we know scans for estimated date and size are not entirely accurate and the margin of error increases as time goes on.

We know that different humans grow and ovulate at different rates.

We know that different women "bake" babies at different rates too.

Inducement carries increased risk but also leaving baby in the womb longer (statistics appear to jump at 42 weeks) does too.

No one can be forced to have interventions no matter the time scale, the NHS is all about informed consent. You are in charge and assisted to healthy outcome by the NHS.

So what can we conclude?

Most babies are fine and arrive roughly on time with nothing to fret about.

Scans are better than nothing for most folk but be aware of the progressive margins of error.

You are aware of the balances. I think it's worth writing a comment in your notes about the differeence in expected date and then try to relax and enjoy your pregnancy.

piprabbit · 31/03/2011 13:43

It just means that an average size is exactly that - an average. Look at the adults you know - the average British woman is about 5'4" tall. But I bet you know women who are shorter and women who are taller than that. Babies are exactly the same. A big baby is just a big baby.

What the HCPs do keep a close eye on is how consistent your baby's growth is. So if you start off with a larger than average baby, but suddenly it starts to drop below average then they might be concerned that your baby is growing more slowly than expected and want to keep and eye on you both more closely.

Original poster

BabydueAugust · 31/03/2011 14:04

Ok it makes more sense now....So maybe the fact i have a bigger baby length or size wise could be the week ahead of my pregnancy?

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Fluter · 31/03/2011 14:44

I shouldn't worry - like piprabbit, mine are IVF, so I know almost to the hour the date of fertilisation etc.

The IVF nurse, at my 7 week scan (7 weeks to the day from fertilisation), when I was showing as 6+3, said it had something to do with dating from the date of implantation rather than fertilisation.

I just reckon they'll turn up when they're ready....

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