Inter- and intra-observer reliability in first-trimester uterine artery Doppler measurements

Objectives: This study aimed to evaluate the inter- and intra-observer reliability of Doppler ultrasound measurements of the uterine artery (UtA) pulsatility index (PI) in the first trimester of pregnancy. Doppler measurement of the UtA is an integral component in algorithms for calculating risks for developing conditions like pre-eclampsia and fetal growth restriction and for deciding which women should be given low-dose aspirin. Methods: This was a prospective observational cross-sectional study, enrolling low-risk singleton pregnant women between 11 + 0 and 13 + 6 weeks of gestation. Two sonographers alternated in performing three sets of transabdominal Doppler measurements of both right and left UtA. The study employed the True Reproducibility of Ultrasound Technique (TRUST) criteria to assess consistency of measurements. Statistical analysis involved calculating intra- and interobserver reliability and the proportion of measurements above the 95th percentile. Sensitivity analyses considered probe type and BMI. Results: A total of 58 pregnant women were included, resulting in 689 UtA Doppler measurements. Approximately 7.7% of these measurements exceeded the 95th percentile corrected for gestational age. Intra-observer reliability showed poor to moderate intra-class correlation (ICC) values. Interobserver reliability showed poor ICC values for the left and right UtA solely, and a moderate ICC for the average of the left and right UtA taken together. There was moderate to very good agreement between observers for measurements exceeding the 95th percentile. Sensitivity analyses revealed consistent results for probe type, but showed inverse correlation between BMI and the ICC of Doppler measurements. Conclusion: The study showed at best a moderate reliability of first trimester transabdominal Doppler PI measurements of the uterine artery, according to TRUST criteria, and were negatively influenced by higher BMI. Continued research and innovation combined with regular training programs can enhance the reliability of both uterine Doppler and biochemical markers, ultimately further improving their clinical utility.