The accuracy rate is very low, many women are pressured into interventions that do more harm than good, and even the mere PREDICTION of macrosomia (large baby) alters the way physicians perceive and treat labor.

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The abdominal circumference is measured at the level of the liver and stomach, including the left portal vein at the umbilical region.

If we assume a fetus is growing normally, biometric measurements are determined by gestational age, and we can estimate the gestational age and thus the due date.

This is preferable to just averaging all values to arrive at an estimated gestational age.

The wide normal range of BPD in late pregnancy must be appreciated.

The strong acoustic shadow behind the femoral or humeral shaft and the visualisation of both cartilaginous ends indicates that the image plane is on the longest axis and is the optimal measurement plane.

The calipers are placed along the diaphyseal shaft excluding the epiphysis.

It is not expected that BPD be used to assess gestation late in pregnancy.

The values from 33 weeks are intended to predict the growth in fetal head size from a known gestation.

If measurements taken after the first trimester are within one week of the gestational assessment taken from menstrual dating then the ultrasound assessment of gestational age confirms the menstrual dates.

If the ultrasound measurements are in agreement and differ from menstrual dates by more than one week prior to 20 weeks a new estimated due date should be calculated and recorded.

It should be noted that errors of about 10% are reported and that even at this level of accuracy it is disappointing.