Can dating scans be incorrect?

[Katearty]

Had my dating scan this week and they put me at 13 weeks instead of 12 weeks. Completely expected as the only way I could have fallen pregnant is if I ovulated at least a week early.

Anyway when my family looked at the scan they all said that the baby looks too developed for 13 weeks...ore like a 15 or 16 week baby.

Bit of back ground... two of them are ex midwives. They felt my uterus and they said it feel further up than it usually would be for 13 weeks.

What they didn't know when they were saying all this was that I was scanned by a trainee and it took 30 minutes to get a measurement due to the baby moving around and not laying correctly.

I'm just wondering if anyone has experienced this as I never considered for a moment that a dating scan could be significantly wrong?

Thanks

Is it not possible to work it out from the first day of your last period?

DC2 is an IVF baby.We knew exactly what day conception happened, but the dating scans were a 5 days out and the hospital insisted on using the dating scan to calculate due date instead of the true dates. I'd take it with a large pinch of salt.

Perhaps get a private scan if possible? If the midwives are correct, then you don't want baby being classed as premature when they're on time, or being pregnant for what feels like eternity because they don't think baby is ready yet.

They told us DS was 2 weeks further than we knew in the first scan, we both knew it was impossible but the nurse didn’t believe us, by the second scan the dates made more sense and DS was born on the due date calculated by us. We have some friends that were told the baby was too small but to be honest, both her parents are very short and there was back then not much you can see in a sonogram.

I would calculate according to your own dates.

Yes, it's absolutely possible, my dating scan for my first child was almost 3 weeks out.
I knew the exact date that I had conceived (ONS).It was all a bit awkward and took an extra bit of trust from my now partner.
He didn't even ask for a DNA, good thing Jeremy Kyle has buggered off incase he changes his mind
Best of luck with your pregnancy.

Yes I think mines at least a week out based on ovulation.

However it's all a bit misleading anyway. Gestation is 37-42 odd weeks. Your due date just helps hospitals plan. Don't be too wedded to it.

Hi,
I had a private scan that said I was exactly 7 weeks with my dates being exactly 7 weeks. I then had another one at 9+3 weeks at at different place and they said 9+3. When I then went for my nhs 12 week scan on exactly 12 weeks they put me at exactly 13weeks. So I jumped 1 whole week ahead. Maybe they can have little growth spurts.

Xxxx

Due dates aren't an exact science anyway, so I wouldn't be too worried. I think they give you one so you get appts at roughly the right time. Of a recent group of pregnant friends, no one has had baby earlier than 10-13 days late!

Oh no @ryanreynolds don't say that! I can't go another 5 weeks 😂

I wouldn't worry too much. I had fertility treatment and know to the day when I conceived, I had a very early scan which gave the "correct"'due date but the nhs 12 weeks scan put my date 6 days later and everything revolved around that despite my protestations that they were wrong!

Anyway he came along, the day after the original due date.

It might cause issues if you go overdue they are trying to induce you before they should but they can't make you.

Ps due dates should be taken like a pinch of salt. Babies take about 38 weeks to be ready to be born (as you are not pregnant for the first 2 weeks of a pregnancy)

The whole "due date" thing is just to make sure you get appointments at roughly the right time.

In France pregnancies are 41 weeks long rather than 40. I'm pretty sure babies gestation doesn't take longer there. Just a different way of estimating the due date.

They measure the length of the foetus (CRL) and assume that it's 'average' so on the 50th percentile and then correlate that to gestational age. Clearly not everyone is going to have a foetus that's bang on that 50th percentile. The later the scan, the more variation there is from that (a paper I read suggested 10 weeks is more accurate than 13 weeks for instance). It's supposed to be more accurate than just going off LMP dates as those assume a 28 day cycle with ovulation occuring on day 14 which isn't going to be right for most women. However if you track cycles with BBT and know when ovulation occured, then that's more accurate than measuring CRL.

And then there's the error from the person taking the measurements. As you say OP, yours were taken by a trainee, so there's a chance the measurements weren't that accurate. If you have concerns - speak to your midwife.