How accurate are due dates?

Question

I had an abdominal ultrasound yesterday and measured at 6W6d. Based on my first day of my last period I thought I was 7W5d. It’s just weird bc if I’m only 6W6d that means I had my BFP on a digital when I was only 7 days past ovulation which seems unlikely 🤔  either date is wrong or baby is growing slowly?

Answer

They're very accurate early on. All babies develop the same in the first 12ish weeks. That's why they do dating scans earlier. If you're concerned that you are farther along than the doctor is saying you are, I would call them and request a repeat ultrasound in a week. If in a week they show baby grew by 7 days it's probably fine. But if there is an issue at least you'll know. Coming from someone who knew her ovulation date and the 1st ultrasound was a week behind and baby was not ok. I hope everything turns out ok!

Answer

Whilst the development of the embryos are similar in most scenarios, the measurements are not as they are subject to sonographer skills, machines etc.
At such early stages, the measurements are minute - in millimeters. Accuracy is +/- 5 to 7 days at this stage.

Answer

I measured 2 days ahead at my first appointment.  From my LMP I was 9w2d but measured at 9w4d.. I had prepared myself to measure a week behind but that wasn’t the case for me.. I’m now 12 weeks 2days

Answer

Unless you know for sure when you ovulated,  there is a chance you could have ovulated a couple days later.  I'm sure everything is fine,  but if you're still concerned call the Dr and let them know

Answer

My due date based on my LMP was really accurate. She was due 9/25 and born 9/24. Based on the scan the due date was 9/30

How accurate are due dates?

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