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Pregnancy

Baby appears to be measuring big for O date...is this an issue?

6 replies

dividedmansions · 31/08/2015 11:54

I will try to explain this as best I can...am a natural worrier and it has been bugging me.

So I MC naturally at 5 weeks at the end of May. By beginning of July I was pregnant again. I had been sort of temping - ie, taking my temperature once every few days (just to check I had ovulated rather than the exact day - my pre and post O temps are always very obvious and I temp vaginally so I don't get off readings really). I was also doing ovulation tests and got a strong positive on 19/20 June. I then noticed a rise in temp the day after or so. So I am fairly certain I ovulated on the 20 June, which would make me 12+1 today.

I have had a few scans in this pregnancy due to a bit of early spotting and the results were:

Scan at what should have been 6+3, baby was measuring 6+4 - not a big deal.

Scan at what should have been 8+2, baby was measuring 8+5. Stlll not much of a big deal I guess?

Scan at what should have been 10+3, baby was measuring 11+1. Seems like a massive leap! This was private scan

I'm due to have my NHS scan on 3 Sept and really worried we will jump ahead again.

If I had my ovulation date correct (which I'm sure I did, it could only have been 2 days out at most really), then I should only be 12+1 today but according to my last private scan I am 13 weeks.

Does anyone think this is an issue? I think there is little point talking to midwife about it because they will just trot out the whole 'oh you probably have your dates wrong' thing.

Sorry for essay, let me know if anything is unclear! Would really appreciate other experiences.

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RockerMummy184 · 31/08/2015 12:10

I wouldn't worry about it. It's only a couple of days. I knew exactly when I ovulated when I got pregnant with DS but the midwife and scans all dated me from the day of my LMP (effectively putting me 2 weeks ahead of where I knew I was) lo and behold, DS was 2 weeks 'late' going by the due date they'd given me (born exactly at 40 weeks going by the date I'd ovulated).
There's around a 5 week margin of error when it comes to babies being born on their actual 'due date' anyway (37-42 weeks is classed as normal term) so I'd not be concerned about a few days discrepancy.

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plonkie · 31/08/2015 12:11

I wouldn't worry! At my 12 week scan I was deemed to be 13 weeks too. I'm now 36 weeks and baby is big but not off the scale and nice and healthy :-).

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dividedmansions · 31/08/2015 12:19

I wouldn't be bothered if I wasn't sure of my O date, it's just I'm pretty sure I am so I don't know why baby is growing so much!

Maybe he/she will just be big :)

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PermetsTu · 31/08/2015 12:25

What is it that's worrying you? That a few days discrepancy means something ominous? Or that it will affect care? Rest easy on both counts.

An early scan can be up to 5 days or so out either way anyway because of the position of the baby, the machine, the scanner, the general inescapable limitations of technology versus biology. You can expect some leeway either way anyway. Plus, you don't know exactly when you ovulated, you only have a few signs to suggest it, you don't know how long implantation took (I always test positive for pregnancy at 9dpo for example, other people don't get positive tests until they're late for their period, it's due to time taken to implant and early hcg levels).

An early scan doesn't tell you when you conceived to the day. It tells you roughly when you conceived (really quite accurate though imo, 5 days is nothing when once upon a time we only had LMPs to go on). The scan tells you that your pregnancy is correctly located, progressing normally etc. I know your history makes you worry but really everything you describe is normal.

RockerMummy, it's normal for them to use your LMP date at first as most women don't know when they ovulate. The scans just give a clearer picture. You're right about the 37-42 weeks thing too. The 'due date' isn't a 'due date' at all. It's just a date around which they arrange care. In France, for example, they use your 41 week date as your 'due date'. It's not a prediction of anything. A normal gestation is between 37 and 42 weeks.

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RockerMummy184 · 31/08/2015 13:34

Oh that's interesting about them using 41 weeks in France. Maybe if they used that principal over here people would be a bit more patient and relaxed in the last few weeks.

I also heard that dating scans earlier that 11 weeks are not as accurate as they are after that time (hence why they have tried to book dating scans between 11-14 weeks even before NT screening was offered). I had no idea how far on I was when I found out I was pregnant this time as I'd not had a period for about 3 months, I was sent for an early dating scan at about 9 weeks. When I went back for my 12 week NT scan they changed my due date as the scan was more accurate at this point.

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PermetsTu · 31/08/2015 13:54

Development before 12 weeks is pretty uniform but it's harder to see with a degree of accuracy as everything is so small. It's a tough one because after 12 weeks, familial and genetic differences start to make a difference but it's also easier to see what you're looking for. A dating scan around 12 weeks seems to be optimum, you're right. Smile

I am a bit of a broken record about due dates. It isn't a prediction and I feel so cross that pressure is put on women and they end up feeling demoralised and unhappy as soon as they hit 40+1. The language we use is ridiculous. The baby is not 'late' or 'overdue' once you go over 40 weeks. People start to mutter about bringing on labour and pineapple and curry and sex and they're utter myths. Total nonsense. No science ever has backed up the notion that a woman can start labour herself. But women up and down the country are eating food they don't want, having sex they can't enjoy and hiking up hills which make them sore. All in the name of this 'due date' which was a nonsense to start with.

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