Date confusion

[ThreeBeanRap]

I thought I was 8+6 today with my first baby. I had some bleeding last week so was referred for an early scan yesterday which thankfully went well, but dated me as 7+2 (7+3 today). I don't understand how that's possible as I am 100% sure of the dates of my lmp (first day of which was 14/02.) can anyone help explain why the dates are different?

Yes, you ovulated late.

I had the same thing - thought I was 9+ ended up being 8+

Nothing to worry about.

Last menstrual period is irrelevant. We only use it because it helps date the pregnancy very approximately before you are scanned. The average pregnancy lasts 38 weeks from ovulation/conception. As the average woman's last period starts 2 weeks before ovulation and once upon a time we had no scans, we just dated pregnancy as 40 weeks from LMP.

However, not every woman ovulates on day 14. Two women can start their periods on the 1st and one ovulate on the 10th, the other on day 24. They have the same LMP but by scan would differ by 2 weeks.

You just don't ovulate on day 14.

Plus scans have a margin of error.

That makes sense. Thank you both!

I ovulated and conceived on day 10 according to my scans!

MissTwister, I always ovulate on day 10. All the best people do...

The early scans can be out about 7 days each way you may find when you go for dating scan at 12 weeks you've gained a few days or even a week. Congratulations

I had an early scan which dated me back a week even though I felt certain about my dates. At my 12 week scan it was moved back again. I think the early scans are hard to date accurately. Don't worry :)