Bpd ultrasound dating table

When the date of the last menses preceding conception is known, it is usually a more accurate estimate ( /- 5 days) of EDCWhen using ultrasound to estimate gestational age, remember that we are assuming the fetus is growing normally.Conditions which alter fetal growth will make the estimates less reliable.These measurements are more appropriately used in the assessment of fetal growth, particularly in the second half of the pregnancy, than in the assessment of gestational age.It is, however, an appropriate measurement in the second trimester to demonstrate normal fetal proportions.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.It should be noted that errors of about 10% are reported and that even at this level of accuracy it is disappointing.It is suggested that there may be an improvement in accuracy of about 5% in using three rather than two parameters.

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The earliest measurement of gestational age taken in pregnancy should usually be accepted as the definitive assessment, subsequent examinations reflecting only fetal growth in the intervening period.Given its inaccuracy and resulting interventions, this does NOT seem to be a justifiable use of the technology unless co-existing conditions like diabetes are present (even then, some research questions its use).However, it does remain common despite the research against it.The reduced accuracy of prediction of gestational age after 20 weeks must be appreciated.At any gestation, if the ultrasound fetal measurements of each parameter are not in agreement, the reason for this difference should be evaluated.

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