Question by  aariel18102 (1)

Is GA on ultrasound based from lmp or fetal age?

My lmp 11/14/09 put my GA at 7wks 5dys with EDD of 8/21/10 but ultrasound on 1/7/10 said GA 8wks 6dys with EDD of 8/13/10. What does this mean? Could I have conceived in October and 11/14 not been a period? Or conceived sometime after the 11/14/09? CRL was 2.2cm


Answer by  LeheckaG (1826)

More-accurate UltraSound/EDDs are usually computer-estimated based on measuring various fetal dimensions via UltraSound-imaging and then comparing/correlating/extrapolating the measurements with a database of statistical measurement averages & sample prior actual delivery dates. LMP/EDD predictions are usually less-accurate unless your cycles are REGULAR & EXACTLY 28 days. If you had November "spotting" (less than a period), it could have been implantation-light-bleeding.


Answer by  danielledc2b (61)

The gestational age is based on a measurement of the fetus at the time. It is an estimate based on your last menstrual period and the size of the embryo at the time of measurement.


Answer by  AidansMomma (106)

Measurements of certain parts of the fetus are used to determine GA, such as the femur, head circumference and crown to rump measurement. It isn't always exact, especially if the ultrasound is done by an ob/gyn instead of an ultrasound technician.


Answer by  Mary (2095)

I was 7 days smaller on my ultrasound. The technician said that the ultrasound can vary from the lmp 12 to 14 days without a change in due date.

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