A 29-year-old female asked:
can a 5 week ultrasound be off by a week or more like a couple days?
3 doctor answers • 3 doctors weighed in
Dr. Addagada Rao answered
General Surgery 56 years experience
Possible few days: Radiologist , interprets pretty accurately , may be off by few days not few wks, as the embryo will follow the clock like pattern , end of 4 , beginning of 5 wk you see gestational sac and fetal pole, speak to your doctor who has more information, good luck.
4964 views
Dr. Amy Levine answered
Radiology 23 years experience
Ultrasound dating: First trimester ultrasound is accurate within 5-7 days. There is no test that can date conception more accurately than a 1 week window.
4964 views
Dr. Joseph Accurso answered
Radiology 29 years experience
Ultrasound +/- 8%: Properly performed and interpreted ultrasound examinations have a variability of 8% plus or minus the measured dating.
Given the dates in the question and assuming a high-quality ultrasound, i would suspect that last menses dating is inaccurate.
Ultrasound dating at 5 weeks 0 days should have a 95% confidence range of 4 weeks 4 days to 5 weeks 3 days which is +/- 8%.
4964 views
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Similar questions
Canada
A 32-year-old female asked:
At an ultrasound, what determines if you are 12 weeks or 12 weeks + 4 days? Are measurements this precise? And the accuracy correlates with your LMP too?
1 doctor answer • 1 doctor weighed in
Dr. Allison Urrutia answered
Obstetrics and Gynecology 14 years experience
Crown Rump Length: At twelve week on ultrasound, the sonographer measures the fetus' crown rump length (crl). This measurement is from the base of skull to tailbone. Ultrasounds at twelve weeks are accurate within 7 days. If you were 12 weeks by LMP and 12 4/7 weeks by sono, you due date would stay consistent with your lmp.
5414 views
Punta Gorda, FL
A 25-year-old female asked:
Can an ultrasound be off by 14 days?
1 doctor answer • 1 doctor weighed in
Dr. Dwain Rickertsen answered
Family Medicine 36 years experience
Family practice : Usually they are pretty accurate. You could have another u/s to confirm dates.
5140 views
United Kingdom (Great Britain)
A 22-year-old female asked:
Periods longer went from 28 to 33 day cycle & last 2 cycles were lighter. Ultrasound results fine. Doc says its likely environmental. Should i worry?
1 doctor answer • 1 doctor weighed in
Dr. Bryan Treacy answered
Gynecology 35 years experience
May be normal: Menstrual irregularity is common. Environmental stressors can induce changes in the hormones that direct the length of the cycle. A normal menstrual cycle usually runs from 26-35 days in length including the menstrual period. This cycle length is not concerning.
5070 views
A 22-year-old female asked:
Im due september the 20th 2013 could I have conceived on 25 th november 2012 i went for ultrasound on 30th of january and i was 6 weeks and 5 days?
1 doctor answer • 2 doctors weighed in
Dr. Diane Minich answered
Family Medicine 37 years experience
No: By the ultrasound you would have conceived around the end of december.
5068 views
Maryville, TN
A 24-year-old female asked about a 26-year-old female:
Can you use ultrasound to help determine paternity if sexual encounters are a month (30+) days apart?
1 doctor answer • 3 doctors weighed in
Dr. Robert Killian answered
General Practice 28 years experience
Early Pregnancy: The early pregnancy ultrasounds are used to get accurate dating of the pregnancy. This is where you can determine this answer.
4904 views
90,000 U.S. doctors in 147 specialties are here to answer your questions or offer you advice, prescriptions, and more. Get help now:
Last updated May 6, 2015
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