Canada
A 32-year-old female asked:

Would the gestational age of 12wks+4days @62mm be off by 1 week since ultrasounds have a margin of error of 1 week in the first trimester?

3 doctor answers4 doctors weighed in
Dr. Craig Keathley
Obstetrics and Gynecology 26 years experience
Estimates: Determination of gestational age is based on estimates determined by the last menstrual period and ultrasound. There is a margin of error with ultrasound, but that does not mean that the gestational age is necessarily different by a week. It means that the ultrasound estimate is 12w4d with a very high likelihood that the actual age is between 11+ to 13+ weeks.
Created for people with ongoing healthcare needs but benefits everyone.
Dr. Larry Grissom
Radiology 45 years experience
Usually +_/- 5-6 day: Gestational age charts are based on averages, as 6 lb. Or 8 lb. Baby can be normal at birth. Dating is based on first day of bleeding of your last menstrual period. The +/- means there is 95% chance that the gestational age is x weeks y days +/- 5 days.
Created for people with ongoing healthcare needs but benefits everyone.
Dr. Randy Baker
Holistic Medicine 42 years experience
Probaby not but...: No test is perfect and fetuses have variable sizes. The results mean the gestational age might be anywhere between 11 wks + 4 days and 13 wks + 4 days, with 12 wks + 4days the most likely. If you know the dates you most likely conceived (about 15 days after your last period began) this would help you better know how far along you are.
Created for people with ongoing healthcare needs but benefits everyone.
Last updated Jun 6, 2015

Disclaimer:

Content on HealthTap (including answers) should not be used for medical advice, diagnosis, or treatment, and interactions on HealthTap do not create a doctor-patient relationship. Never disregard or delay professional medical advice in person because of anything on HealthTap. Call your doctor or 911 if you think you may have a medical emergency.