NHS Date v IVF clinic date

[KJM2013]

Hi, just come back from my 12 week scan which was done on what I believed to be 13+3. They have dated my pregnancy as 14+1, not massive differences but my date was calculated based on the day a 5 day blastocyst was transferred at my IVF clinic. This date was then agreed to at an 8 week and 11 week private scan.
Can the NHS one be wrong? Obvs they are now basing everything off this and I know its only a few days but I am having an elective c-section and if they don't let me go full term, I'll have it in August. My other daughter is a later summer baby and I worry about struggling at school (I know far too early to worry about these things!)

What is your new DD and your previous DD? Have you told the person doing the scan when the embryo was transferred ? The NHS really piss me of with this, I had an early scan last week and she said I was measuring 6 weeks, i said that was impossible because 6 weeks ago I was on my period 🧐 the same happened with my DD I knew when I ovulated but they said I was a week further than i was 😒 xx

My ivf clinic said to base it on day of egg collection being day 14/week 2 as that's the day the egg was fertilised.

I've only just had my positive test last week so not as far along as dating scans. Back to the private clinic for a 7 week scan in 2 weeks

I go from 8/9 to 3/9. If I was going natural, I know it would be late and this would be a non-issue but as likely to have elective c-section might end up with August baby.

My ivf clinic said that as long as it was dated within a week it was ok. The dating goes by measurement at this stage and isn't totally accurate. Some babies are slightly bigger than other which means a difference of a couple of days.

I'd go by the IVF date. The NHS hospital I'm under uses that even if their dates are a bit different at the dating scan and won't change it. Did the sonographer know you had had IVF?

Go by the ivf date. At my 12 week scan, I was 5 days ahead. I'm now 39+5 and the growth has massively slowed. We went from 90th centile down to 30th now...

I get the feeling that all this dating/ growth stuff is more art than science.