Clinical interpretation of ultrasound biometry for dating and for assessment of fetal growth using a wheel and chart: is it sufficiently accurate?
OBJECTIVES: To investigate how accurately practicing obstetricians (experts) can apply dating rules and compare the interpretation of gestation-sensitive ultrasound data with those of a computer system. SUBJECTS: Seventeen practicing obstetricians. Members of the Royal College of Obstetricians and Gynaecologists, from 14 different units throughout the UK. DESIGN: Six cases with menstrual and ultrasound data together with identical ultrasound charts and obstetric wheels. MAIN OUTCOME MEASURES: Concordance between the calculated estimated date of delivery (EDD) and growth assessment provided by the experts and the computer system. RESULTS: The calculation of the EDD by the experts was imprecise (59% within 3 days overall). Concordance with the computer calculation was poorest when the ultrasound measurements lay close to the upper or lower centile lines (average 7% within 3 days of the computer). Interpretation of growth showed good concordance with the computer when gestation was not critical to the interpretation (94%), but very poor when gestation was critical (7%). CONCLUSIONS: Calculation of EDD by means of an obstetric wheel and charts is not precise. Compared with the computer system, these errors have a significant effect on the subsequent interpretation of growth scans when the data are borderline. A computer system provides the more accurate method for interpreting gestation-sensitive ultrasound biometry.