A 31-year-old female asked:
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lmp says edd 7/24/14 but first vag u/s says 7/20/14 does that mean i ovulated 10days after lmp rather than 14days?

1 doctor answer
Dr. Charles Whiting
26 years experience Obstetrics and Gynecology
U/S not perfect: The error in an early first trimester u/s is +/- 5 days. If the u/s measurements calculate a due date of 7/20/2014, it means your "real" due date could be as early as 7/15/2014 or as late as 7/25/2015. Your LMP due date is within the accuracy range of the u/s. You are correct that LMP is somewhat imprecise. Not all women ovulate 14 days after the first day of your period.
Answered on Feb 13, 2015

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