Inter-operator reproducibility of ultrasound measurement of three foetal biometric parameters: comparison of experienced sonographers and radiography interns

Nneoyi Onen Egbe, Ernest Usang Ekpo, Christian C Nzotta


Background: The dearth of experienced sonographers in Nigeria has created an all-comers environment in which many would-be sonographers enter the field with minimal supervision giving rise to the question of competence of personnel and, often, the accuracy of results obtained.

Objective: To assess inter-operator reproducibility in the measurement by sonographers and radiography interns of three common foetal biometric parameters: bi-parietal diameter (BPD), femur length (FL), and abdominal circumference (AC).

Method: Twenty (n=20) women, carrying normal singleton fetuses of between 20 and 40 weeks gestational age, consented to participate in the study. They were evaluated in three ultrasound centers. Ultrasound scans were performed on all of them. Biometric measurements were obtained following standard protocols. Foetal biometric measurements (bi-parietal diameter (BPD, femur length (FL), and abdominal circumference (AC) were performed independently by one sonographer and one intern who were blinded to the purpose of the study and the figures of the other participant in each centre. Coefficient of variability percent was used to assess inter-operator variability. Intra-class correlation coefficient (ICC) at a 95% confidence interval was used as a metric to compute weighted kappa (Kw) to assess inter-operator reproducibility of measurements.

Results: Coefficient of variability (COV %) ranged from 0.84 – 1.79, and the mean coefficient of variability was below 2.0 % in all locations for all measured parameters. Intra-class correlation coefficient, indicating between operator agreement ranged from 0.95 – 0.98 for BPD, 0.90 – 0.91 for FL, and 0.92 – 0.99 for AC. The overall agreement for all centers was 0.94 ± 0.04; P=0.0001.

Conclusion: Sonographic measurements of fetal biometric parameters measures of experienced sonographers are highly reproducible by interns undertaking ultrasound training.


Gestational age, obstetric ultrasound, femur length, bi-parietal diameter, abdominal circumference

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The South African Radiographer | ISSN 0258 0241

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