Is the B-ultrasound estimated weight overestimated or underestimated?
Recently, I went to the hospital for an ultrasound to estimate the baby's weight. I would like to ask, does the ultrasound estimate tend to be heavier or lighter?
Doctor's answer (1)
The accuracy of fetal weight estimation by B-ultrasound is influenced by various factors. Generally, the estimated weight obtained via B-ultrasound may be either higher or lower than the actual weight, primarily depending on fetal position, measurement methods, and individual differences.
According to statistics, the average error rate for fetal weight estimation using B-ultrasound is approximately 10%. This means that if the B-ultrasound indicates a fetal weight of 3500 grams, the actual birth weight could range between 3150 grams and 3850 grams. However, the estimated weight by B-ultrasound could be either higher or lower, depending on factors such as maternal body shape, amniotic fluid volume, fetal position, fetal posture, and the operator's experience.
In addition, the posture of the fetus within the uterus directly affects the accuracy of B-ultrasound measurements. When the fetus is in an unfavorable position, the measurements may be either smaller or larger than the true values. Moreover, each fetus develops uniquely, so there is always some degree of error between the estimated fetal weight by ultrasound and the actual birth weight. This error typically falls within approximately 10%, which equates to a difference of about 500 grams.
