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Assessment of Child Anthropometry in a Large Epidemiologic Study

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Published on: February 2, 2017

Expected-value bias in routine third-trimester growth scans.

L Drukker¹, R Droste², P Chatelain²

¹Nuffield Department of Women's & Reproductive Health, University of Oxford, Oxford, UK.

Ultrasound in Obstetrics & Gynecology : the Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology

|November 26, 2019

Summary

This summary is machine-generated.

Expected-value bias is common in fetal growth scans, affecting measurements of head circumference, abdominal circumference, and femur length. This bias can alter estimated fetal weight, potentially misclassifying fetal growth.

Keywords:

artificial intelligence ascertainment bias detection bias expectancy bias eye tracking fetal biometry growth scan observer bias observer effect ultrasound

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Area of Science:

Prenatal diagnostics
Medical imaging
Obstetrics and Gynecology

Background:

Operators performing fetal growth scans often know the gestational age, potentially introducing expected-value bias.
This bias can influence biometric measurements, impacting accurate fetal growth assessment.
Understanding the incidence and impact of this bias is crucial for improving diagnostic accuracy.

Purpose of the Study:

To evaluate the incidence of expected-value bias during routine fetal growth scans.
To assess the impact of expected-value bias on standard biometric measurements (HC, AC, FL).
To quantify the effect of bias on estimated fetal weight and growth classification.

Main Methods:

Collected prospectively video recordings of routine ultrasound growth scans with operator eye tracking.
Defined expected-value bias as operator focus on measurement box during caliper adjustment.
Analyzed 272 third-trimester scans measuring head circumference (HC), abdominal circumference (AC), and femur length (FL).

Main Results:

Expected-value bias occurred in 91.4% of saved biometric measurements.
Measurements were frequently adjusted towards the expected gestational age (47.7% vs. 19.7%).
Bias led to significant discordance in estimated fetal weight (up to 10.1%) and potential misclassification of fetal growth.

Conclusions:

Expected-value bias is highly prevalent in routine third-trimester fetal growth scans.
This bias significantly alters standard biometric measurements and estimated fetal weight.
Awareness and mitigation strategies are needed to improve the reliability of fetal growth assessments.