Inter- and Intraobserver Agreement in First Trimester Ultrasound Evaluation of Placental Biometry

Objective: The aim of this study was to assess the clinical applicability of a new analytical software program by determining the inter- and intraobserver agreement for 2D placental biometry and three-dimensional (3D) placental volume (PV) in the first trimester. Methods: A prospective study of 25 singleton pregnancies between 11 and 14 weeks was conducted. 3D datasets were captured, and PV was estimated using the Phillips QLAB GI3DQ ultrasound quantification software. The basal plate (BP), chorionic plate (CP), placental thickness (PT), and the free uterine surface (FUS) area not occupied by placenta were considered for 2D biometry evaluation. Each variable was measured in 2 orthogonal planes with mean values used for the analysis. Intra- and interobserver agreement was evaluated. Results: Intraobserver agreement for both 2D and 3D measurements was high, particularly for the PV and PT (interclass correlation coefficient [ICC] 0.989 [95% confidence interval (CI) 0.97-0.99] and ICC 0.936 [95% CI 0.86-0.97], respectively). Interobserver agreement was good for the PV (ICC 0.963 [95% CI 0.91-0.98]), PT (ICC 0.822 [95% CI 0.63-0.91]), and CP (ICC 0.708 [95% CI 0.44-0.86]), but moderate for BP and FUS. Conclusions: PV, PT, and CP are reproducible measurements to evaluate first trimester placental biometry. Further research is needed to assess the clinical utility of these variables as predictors of poor obstetric outcomes.