ultrasound question

Does anyone know how accurate ultraosunds are in determining the age of
fetus? And, when they tell you "age of fetus," is that from the time of
conception? Any input is greatly appriciated. Thanks all!

"ECM" wrote in message
oups.com...
Does anyone know how accurate ultraosunds are in determining the age of
fetus? And, when they tell you "age of fetus," is that from the time of
conception? Any input is greatly appriciated. Thanks all!

Well the official story is that it is accurate for before 12 weeks. Actually
it isn't that accurate anyway. I wasn't given a fetal age, just an adjusted
edd.
Debbie

from "last menstrual period" or about 2 weeks before ovulation.

Right. If you subtract 14 days from the menstrual age (which is most
often used in obstetrics) you get the approximate age since conception.

first trimester it's considered accurate +/- 1 week
second trimester it's accurate +/- 2 weeks
third trimester...+/- 3 weeks.

That is a general rule of thumb, but actually if the dating estimate is
based on a crown-rump measurement from 8 to 12 weeks, it should be
accurate +/- 5 days.