A 32-year-old member asked:
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can an ultrasound measure baby weight? i had an ultrasound done and the doctor used it to estimate my baby's weight. how accurate are these estimations?

2 doctor answers
Dr. Geoffrey Rutledge
40 years experience Internal Medicine
A : A baby's weight is calculated based on measurements of the width of the head, the head circumference, the length of the femur bone, and the abdominal circumference. These measurements are then entered into a formula which generates an estimated fetal weight. This estimation also comes with a calculated range of error. The estimated fetal weight is generally more accurate early pregnancy and becomes more variable later in pregnancy. At term, the estimated fetal weight can vary by more than 1 pound from the baby's actual birth weight. At the time of your ultrasound, you may want to ask the ultrasound technologist the range of error for the estimated fetal weight of your baby. The radiology report sent to the obstetrician also often includes this error range.
Answered on Oct 3, 2016
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Dr. Boris Aronzon
23 years experience Anesthesiology
Accuracy: These estimates are accurate. If there is reason for concern, doctor will let you know.
Answered on Apr 26, 2013
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Dr. Cynthia Palabrica
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Ultrasound: The measurement given to you is within the error of the machine.
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