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How to calculate conception date from ultrasound

A 24-year-old female asked:
Dr. Paul Slawek
Radiology 55 years experience
Measurements: US uses measurements of the gestational sac and then the growing fetus to date a pregnancy. The appearance of the heart beat. Usually measurements are... Read More

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A 41-year-old member asked:
Dr. Michael Gabor
Diagnostic Radiology 34 years experience
The margin: of error for ultrasound pregnancy dating is about 8%.
A 19-year-old female asked:
Dr. Raj Syal
Dr. Raj Syalanswered
Obstetrics and Gynecology 34 years experience
7-10 days: Usg can predict conception with a accuracy of 7-10 days at this gestation.
A 28-year-old female asked:
Dr. Robert Killian
General Practice 29 years experience
Five Days: The standard answer is that sperm live up to five days after emission. So the closest they can come to is a five day window around conception.
A 32-year-old male asked:
Dr. Miguel Cano
Obstetrics and Gynecology 31 years experience
You have a Problem: Check your dates... If you really had an ultrasound 5/23 and you were 26 weeks & 1day...Your due date would have been 8/28/12 & you'd be 49 weeks & 4 ... Read More
A 33-year-old female asked:
Dr. David Dinhofer
Radiology 42 years experience
Depends: The accuracy of the delivery date is variable depending on a number of factors. Usually the earlier scan is most accurate due to differences in gesta... Read More
A 32-year-old male asked:
Dr. Gayane Ambartsumyan
Fertility Medicine 21 years experience
Jan 27: You are approximately 27 wks and 5 days and due date jan 27th. Please talk to your doctor for more accurate details as she knows your history the bes... Read More
A 22-year-old female asked:
Dr. Larry Grissom
Radiology 44 years experience
Within about 10 days: The ultrasound dating is calculated from the first day of bleeding from your last menstrual period ± 5 days.
A 32-year-old female asked:
Dr. Carri Warshak
Specializes in Obstetrics & Gynecology - Maternal Fetal Medicine
1/7/2014: Is the best estimation of the date of conception. The 8 week ultrasound establishes your due date +/- 5 days. Therefore it could be few days before ... Read More
A female asked:
Dr. Gerard Honore
Fertility Medicine 30 years experience
No: Actual delivery date does not change anything calculated form a good 7 week us, the us is the most reliable.