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Confused About U/S Dates...

1 posts on this thread and the last post was on August 9th, 2008 5:27 PM
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bandbaby1 - August 8th, 2008 4:38 PM
 [Original Post]

My LMP was May 30, 2008. I got a positive pregnancy test on July 7. Based on my LMP I would have been 10 weeks today, but according to my ultrasound I'm only 8 weeks 5 days today. The date doesn't add up to my last period, or the day I thought I had ovulated. So I guess my question is, when they tell you a date based on the U/S, have they added in the 2 weeks between your period and ovulation date? I know the date they gave me isn't too far from what I thought it should be, but why doesn't it add up? I'm sooo confused...

sunshine7610 - August 9th, 2008 5:27 PM

The days don't add up because you probably ovulated later than expected. When they calculate how far along you are using your period, it is based on a 28 day cycle. When measuring the baby with u/s it too includes the first 2 weeks from your period to conception. So b/c the baby measures a bit smaller, than you didn't ovulate when you thought you did and your LMP isn't accurate to predict your due date. If you ovulated on cd14 as in a 28 day cycle, than your gestational age from your LMP and from the u/s would be the same. Hope that helps!