Can early ultrasounds be off by a few days?

Question

My first ultrasound measured the sac at 5w2d and the fetal pole at 5w5d. Here's what happened:
​My progesterone level was 13.6 on aug 29th indicating that I ovulated, my hcg was neg. sept 4th my urine preg test was positive. My hcg levels from my previous pregnancy went back to 0 on July 21st. So sometime between July 21st and aug 29th I ovulated. I think I'm more like 5w3d now but could the dating scan be wrong?

Answer

According to the dates we went through the IVF process I'm 12w today. At the 7w scan the baby measured smaller and according to that date I'd only be 11w2d. Because the scans go by the average measurement and are not considered 100% accurate, our midwife told us to keep the original date. So it is possible to be out, and from I can tell early scans are tricky as things are so small then, but grow very quickly.

Answer

My BBT indicates ovulation July 17, and the BD happened July 15. My ultrasound estimated 6 weeks. 1 day and I calculated 6 weeks, 5 days. So I have MY due date (Apr 9) and they have theirs (Apr 13). My midwife says measurement error is normal... But I'm sticking with my date because it's based on better data.

Answer

A few days isn't much, your due date can go two weeks either way anyways and it is rare to even have your baby on your exact due date. I wouldn't be concerned.

Answer

The one my ob did at 9 weeks 5 days said the baby only measured at 9 weeks 3 days but he said that's fairly normal and to keep my edd.

Can early ultrasounds be off by a few days?

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