Measuring behind at 7 week scan

[luckyforsam]

I recently went for an ultrasound due to spotting at what should have been 7 weeks (based on ovulation test, not LMP), we got to see a heartbeat and everything looked pretty good.

The sonographer mentioned in passing, she would say around 6 weeks but stick with my dates as it can be hard to measure. She didn’t seem concerned by this, but I definitely am.

Is this something I should worry about?

Scan photo attached for some sort of reference, I guess.

No you shouldn't be worried at all if you've seen a heartbeat. There can always be variation in the number of weeks because it depends how quickly or slowly fertilisation took place after ovulation. It could have been the day of or up to a week after. Congratulations.

My youngest measured behind in all her scans. I had a scan at what I thought had to be about 7-8 weeks, but she only measured 5-6. She was always small on the scans, most showing her measurements in the 9th-25th percentile, but she was born full term at 8lb 4. They are so tiny at that gestation, a measurement that can be put by a fraction of a mm, can affect the date by a week. In contrast to this, my eldest was always measuring big on scans, was told she was going to be a big baby, ans had to have additional scans, but she was actually only 3ozs bigger than the one they said was tiny.