Measuring smaller than dates at 12 week scan - significant?

[goosey123]

I'm doing my own head in, waiting to be rescanned next week and amnio, after a rare situation was picked up on my CVS. I've been told that the best outcome is probable growth retardation during the pregnancy. Great.

Anyway, I know time will tell what is going on, but I'm twitched that this is already manifesting itself as when I had my 12 week scan, they dated me 5 days behind my calculated dates based on my last period. I know exactly when conceived etc, on the scan date I should have been 12 + 3, and they said I was 11+5. No-one seemed worried at the time, nor was I, but now new CVS results have come to light, they seem more bothered. And so am I.

Is it quite common to have dates changed at this 12 week scan? Have others measured smaller than they should have, and was anyone bothered?

I think its very common to have dates changed at your 12 week scan, usually +/- up to a week seems normal. Mine was only brought forwards by 2 days this pregnancy (although the estimated date was a total guess as my cycles vary between 24-46 days, so it was actually a v good guess). I think in my last pregnancy the dates moved forward by 7 days.

TBH I don't personally know anyone whose due date stayed the same at the 12 week scan, although I'm sure there must be some. So basically, yes, it's very common!

Even if you know when you conceived, the time taken for implantation can vary. And then when the sonographer is measuring such tiny measurements there's going to be some margin of error in those. For example, a good friend of mine had her baby via IVF, so they knew exactly when they had introduced the embryo, but her due date still changed by a few days at her 12 week scan.

I'm sorry to hear about your CVS results though, and I truly hope you and your baby will be [relatively] ok. Best of luck.

Thanks for your response Emu. I will stop googling and wait to see what next week brings.....