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.