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Any midwives out there - what's the official guidance on determining due date?

(40 Posts)
FruitSaladIsNotPudding Thu 22-Nov-12 18:32:00


I have an issue - I am 40+1 today by my dates but according to my 13 week scan I am 40+6. My hospital likes to induce at 40+12. I have already declined induction at that date on the basis the dates are wrong, but my midwife wants me to go into hospital anyway to start monitoring etc on that date (next weds.)

They will not change my dates, and are putting pressure on me re. meeting the consultant next week. But I want to wait - I feel like I want to give this baby a chance to come naturally, and whilst I'm not against monitoring, I feel like it's massive overkill to start at what I know is just 41 weeks.

Btw, I was using ovulation testers when I conceived, so I am pretty certain of my dates.

What I really want to know is what is the official guidance on determining dd? I would be really grateful if any midwives/docs could signpost me to some relevant literature. They won't take my dates into account at all. I have looked at the NICE website but can't find anything.

Of course, I hope I'll have the baby before then, but I feel really stressed about this, which isn't helping!

VikingLady Wed 28-Nov-12 12:52:47

That article (thank you Worley) says that head shape plays a part, too. DD and I are both dolicephalic (longer front to back than side to side) which gives a falsely "young" age. Problem solved!

So maybe it is down to head shape! Maybe we should be asking about crown-rump length as well, and picking whichever is closest to the dates we think are right!

VikingLady Wed 28-Nov-12 12:49:33

My scan date put DD's conception at a fortnight after I know I last had sex. TTC was such a chore after a while that I KNOW I didn't have sex (or do anything else involving sperm) after that date. She was born 10 days late according to my dates, and 5 days early according to the hospital. She was clearly overcooked with no vernix, long fingernails... And my family always deliver 10 days late, on both sides.

Don't know how that happened. Don't know if she had an unusually small head - I had it measured a couple of times in her first few months out of curiosity, and it is 25th percentile where her height is 91st, so it is possible.

Unless DH is very very stealthy....... grin

I don't agree with my scan dates. I think they are a week out. I'm officially due on the 31st January but by my dates I'm due in the 24th. Not that anyone pays the slightest bit of attention.

Being dated a week further on bothers me because when ds3 was born at 40+3 there was some signs of the placenta beginning to become less efficient when it was examined. So if that was to happen again then the extra 7 days would matter. But, I couldn't see anything written in my notes from ds3 even mentioning the placenta so I have nothing to back up my case.

I've had extra growth scans as according to the charts I have small babies - 6lb 14oz has been my smallest and I don't think that's tiny. In every scan I've had with 4 pregnancies the babies have consistently measured on the 9th percentile - it's just the way I grow babies I think. This one is no different, he was on the 9th percentile at my 28 week scan a couple of weeks ago. Because he is a small baby changing my dates isn't even considered as on option. It's hard to be in a position where your opinion is so roundly ignored.

I changed the dates myself on my green notes and in a few weeks will photocopy the scan chart (after my 34 week scan when all scans are finished) and adjust it to my dates before stapling it back in. Probably not the best thing to do but what else can you do when no one will take your concerns seriously.

carrielou2007 Sun 25-Nov-12 18:35:05

I've always heard that sonigraphers are most particular how they word things. At my 20 scan for dd I was told she would be a '9lb er' had dates moved, measured big, she was 9lb 6 with z head likd z watermelon grin. Same lady (sorry can't spell it!!) scanned ds and said same thing and tex he too had huge head - at 2.9 he wears age 6-7 hats!! Wonder what to look forward to at 20 week scan on tue grin

FruitSaladIsNotPudding Sun 25-Nov-12 17:45:12

No other reason, I'm low risk. Anyway, started having irregular contractions today so hopefully problem will be solved soon!

fraktion Sun 25-Nov-12 13:29:46

DS was 4 days out which made conception impossible for me. Early labour started on what I said would be my EDD and DS was born the next day.

I told them it was impossible for their dates to be right and that I would be opting for expectant management to which they hummed and hahed but they can't make you do anything. Obviously if they have a reason for advising otherwise it's different but 'hospital policy' doesn't cut it for me.

RooneyMara Sun 25-Nov-12 13:21:43

Thanks, Orbis - no they just said 'strange things happen sometimes'!

I'm white, British, standard issue head I think grin

Well, I'll just see how it goes.

OrbisNonSufficit Sun 25-Nov-12 10:33:31

Worley thanks that's really interesting.

Rooney, it sounds like you should stick to your dates. As you say, their dates have to be wrong - no sperm and no egg available = no baby. Have they given you any alternative explanations (other than immaculate conception)? Apparently baby head shape (e.g. due to different ethnic backgrounds) can affect the accuracy of the head diameter measurement.

RooneyMara Sun 25-Nov-12 10:15:01

Oh, thankyou Worley - very good of you to answer me!

I am shocked that people get up and walk out. It must be very awkward!

I guess I won't know ever, when exactly he was conceived or meant to be born. So we'll wing it and try our best to avoid induction...I wouldn't object to daily monitoring, I'm only 5 mins from the hospital. And wouldn't want to put him at risk.

I keep wondering though if I actually conceived the prior cycle though and am due in 2 weeks, not 6! hmm Oh dear. That's what my mum thinks anyway. She was convinced I was pregnant well before I knew I was...

Worley Sun 25-Nov-12 10:10:24

Rooney sometimes there are no answers! sometimes conception is a few days after intercourse. it is bizarre..
I've had people swear blind that it's wrong and it can't be that. (I've seen men get up an walk out as they sit there and work out in their head that they weren't about 12 weeks ago) the dates are only as good as the measurements taken. and it it not the best scan then there is alway a margin of error which is why we give a 5 day scope. when I tell people their edd I always say making you around 12+5 (for example) an delivery will be around ddmm when ever baby is ready.

RooneyMara Sun 25-Nov-12 09:26:59

Worley that is really interesting and helpful.

When I went for what was meant to be my 13 week scan, she said Ooh, the baby looks a bit big - and he was off the scale, for the NT measurement and going by his head, she said he was 14+5, and the the computer altered it to 14+3. I had to have the quad test.

The thing is, my dates can't be what they say - I hadn't had sex for aboput 8-10 days when they reckon I conceived, I was on about day 1-4 of my period, and my temps were low until about a week later when they went up as per usual ovulation pattern - I also didn't have a positive OPK till this time.

So I reckon that they are 9 days out, or at least 6. They said there was a +/- 7 day accuracy.

What I wondered was what else might cause a baby to be so big - he was still on the same trajectory at 20 weeks which makes it look like they are right - but it just seems impossible I could have conceived that early.

I wondered if it might mean I have GD or something, or that he is just huge?

They said he is in proportion, not just a big head or something - everything is about right. So I can't work out if I've had a very weird, almost impossible conception, or if I'm having an enormous baby, or if there could be something wrong with him iyswim. It must be one of those things.

Also I don't know when I'll be 'late' - 9 days is an awful long time difference when they want to induce after 41 weeks or so.

Worley Sun 25-Nov-12 07:08:43

ultrasound dating charts article

Worley Sun 25-Nov-12 06:59:13

orbis... the fetuses are measured from the beginning onwards.. we work forwards not backwards. hundreds and hundred of fetuses were measured and their gestational ages were calculated and it is from these charts the percentiles were arranged. there is a wide variance of normal from 25th to 75th percentile. At the early stages to almost 20 weeks all babies are approx the same size.. If one shows up very small or very big then this is when problems are highlighted.. with in the first and towards mid trimester heads are the same size also.. if it was a big head at 12 weeks compared to the body then this is highlighting a medical problem and we have to look in to why.. there are lots of syndromes at this stage which could be reasons.

I will just add that the charts used now were calculated from ususing Caucasian babies.. the charts do not fit with babies from some ethnic origins and should be taken with a pinch of salt.
what is really needed is a new study to be done and to take in to account the wide variance of ethnicity in this country now compared to 30 years ago. maybe prof nickolaides will do one..
sorry for typos am on phone..

nickelbabeuntiladvent Sat 24-Nov-12 23:34:40

you don't need to argue, just keep repeating " i believe my dates are wrong" and "nice guidelines state..."

i was homebirth too.

StarlightMcKenzie Sat 24-Nov-12 20:26:33

Fruit, you don't have to have an argument or a battle. You don't have to convince anyone of your reasons. In fact, you don't even have to HAVE a reason.

You will probably develop a better relationship with your caregivers if you DO have a reason but it is your right to refuse intervention or transfer to hospital for no reason.

fuckwittery Sat 24-Nov-12 19:40:58

i was told by the sonographer that there was a +/- 7 day margin of error for a scan done at 12 weeks. Just say, no thank you to induction. Ask for extra monitoring. See the consultant if you want, mine was great, it was the MW pushing for induction (even though this is extremely risky after a first c-section, risk of scar rupture much higher than the verrry slight increased risk of harm from going overdue!) consultant was happy for me to go to 40+14 with daily monitoring in the last week. in actual fact I went 18 days over due. they were also not delighted about sending a mw to my home but agreed to do so. good luck!

FruitSaladIsNotPudding Sat 24-Nov-12 19:34:49

Thank you so much for the links nickel. I'm just so annoyed they won't listen to me re. dates. I know i can (and will)refuse early induction, but i don't need the stress of having the argument with them. Hardly going to help me go into labour!

I'm booked for a homebirth too, so am worried I'm going to have a battle on my hands over that as well.

Here's hoping i go into labour tonight/tomorrow!

OrbisNonSufficit Sat 24-Nov-12 18:41:57

This is such an interesting thread, I've always been baffled by how this works. For those of you who know how the dating scan works - how much variance is there in baby head size during development (ie how often is the dating scan inaccurate because of big or small headed babies) and how do they know how big the baby's head is supposed to be (ie there is variance in how long a pregnancy is +/- a couple of weeks, you would only be able to measure head size:age correlation based on working backwards from birth, but you don't know if the birth is exactly at 40w therefore you don't know if the measured head size is exactly at that age IYSWIM - so surely the data must be prone to inaccuracies)?

nickelbabeuntiladvent Sat 24-Nov-12 18:34:21

it's okay Rooney - i've been there , done that, been shouted at by an hysterical Reg who was convinced I was going to kill my babeeeeeeee

RooneyMara Sat 24-Nov-12 18:31:29

Thankyou so much for all the links Nickel smile

SchroSawMummyRidingSantaClaus Sat 24-Nov-12 18:26:31

I don't believe the dating scan is very accurate.

With DS I was using conception indicators as well and had a regular cycle. At my first scan I was pushed a week ahead then another something says ahead days ahead on another later scan.

DS was born (by induction) at 38+2 their dates and 36+5 by mines.

There could be no margin of error by my dates as we only had sex once that month and that was the day I got the positive conception test.

We were also told after a scan to expect a 9 and a half pounder, he was 6,1 when he was born. hmm

nickelbabeuntiladvent Sat 24-Nov-12 18:16:27

this is a copy of an article in a midwives' magazine

nickelbabeuntiladvent Sat 24-Nov-12 18:12:49

another link

and google "nice guidelines refusal of induction"

RooneyMara Sat 24-Nov-12 18:09:37

Oh this is dates have been put back by about 9 days since my 12 14+3 week scan.

I was meant to be due on 16th January according to LMP, and 13th according to when I think I conceived (OPK + temping chart) but they have me down for the 7th now.

So I'm worrying about being pressured to be induced, too.
I hope you can figure it out and do what you feel is best x

nickelbabeuntiladvent Sat 24-Nov-12 18:08:03

i think it's this document you need

just remember, they can't force you to do anything, and that NICE recommends that you aren't classed as overdue until 40+14, and that if you believe that 40+14 is different from their guess, then you can force them to go by those fates.

write it down in your antenatal notes on the "other thing i might want to ask" pages (ie the blank ones) "i believe my dates to be wrong and i am using ddmmyyyy as my due date. I insist that my birth plan is worked around this"
if you need to, force your MW to sign that she's read it.

if they start to get heavy state "i am opting for expectant management" which they will try to start from 40+12 (date of refused induction)
and quote NICE guidelines that you have read, over and over again.

and good luck smile

(ps, DD was born 40+16 and she wasn't red or wrinkly at all)(my dates were accepted as correct)

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