Interobserver and intraobserver variability of fetal and maternal Doppler measurements: systematic review and meta-analysis.

OBJECTIVES: To evaluate the variability and reproducibility of umbilical artery (UA), fetal middle cerebral artery (MCA) and uterine artery (UtA) Doppler ultrasound measurements in pregnancy. METHODS: A systematic search of MEDLINE, EMBASE and the Cochrane Library (CENTRAL) was conducted from inception to 17 June 2024. Studies were included if they reported intra- or interobserver variability of UA, MCA or UtA Doppler ultrasound measurements in singleton or multiple pregnancies, using the intraclass correlation coefficient (ICC), concordance correlation coefficient, Cohen's kappa or limits of agreement. Data extraction was performed using standardized data-extraction forms. A meta-analysis was conducted using a random-effects model to account for heterogeneity, and variability estimates were pooled using Fisher's Z-transformation. Reproducibility was categorized according to the True Reproducibility of Ultrasound Techniques (TRUST) criteria. RESULTS: In total, 2426 records were screened. Of these, 26 studies including 2457 patients met the inclusion criteria; eight studies described UA Doppler, 11 described MCA Doppler and 11 described UtA Doppler results; two of the studies described cerebroplacental ratio results. The pooled intraobserver ICC for UA pulsatility index (PI) was 0.88 (95% CI, 0.77-0.94) and the pooled interobserver ICC was 0.68 (95% CI, 0.55-0.79). For MCA-PI, these values were 0.85 (95% CI, 0.69-0.93) and 0.80 (95% CI, 0.62-0.90), respectively, and for mean UtA-PI they were 0.90 (95% CI, 0.85-0.93) and 0.84 (95% CI, 0.78-0.89), respectively. Findings across studies suggested generally poor-to-moderate reproducibility according to the strict TRUST criteria. CONCLUSIONS: Our results emphasize that there is room for improvement regarding the reproducibility of Doppler ultrasound in routine obstetric practice. By standardizing ultrasound measurement protocols, advancing technologies such as artificial-intelligence-supported measurement applications and training programs, as well as obtaining multiple measurements per session and performing quality audits when outliers are detected, the field could move towards more accurate and reliable fetal assessments. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.