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-sensiti ve ultrasound data with those of a computer system. Subjects Seventeen practicing obstetricians, Members of the Royal College o f 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 comput er system. Results The calculation of the EDD by the experts was imprecise (59% within 3 days overall). Concordance with the computer calculation was poorest whe n the ultrasound measurements lay close to the upper or lower centile lines (average 7% within 3 days of the computer). Interpretation of growth showe d 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 signif icant effect on the subsequent interpretation of growth scans when the data are borderline. A computer system provides the more accurate method for in terpreting gestation-sensitive ultrasound biometry.