Introduction: The availability of imaging makers of early placental circulation development is limited. This study aims to develop a reliable and accurate method to assess preconceptional and early first-trimester utero-placental vascular volumes using three-dimensional power Doppler ultrasound (3D PD US) on two different Virtual Reality (VR) systems.
Methods: 3D PD US images of the uterine and placental vasculature were obtained in 35 women, either preconceptionally (n=5), or during pregnancy at 7 (n=10), 9 (n=10) or 11 (n=10) weeks of gestation. Preconceptional uterine vascular volume (UVV), and first-trimester placental vascular volume (PVV) and embryonic vascular volume (EVV) were measured by two observers on two VR systems, i.e., a Barco I-Space and VR desktop. Intra- and inter-observer agreement and intersystem agreement were assessed by intra-class correlation coefficients (ICC) and absolute and relative differences. Results: Uterine- , fetal- and placental vascular volume measurements showed good to excellent intra- and inter-observer agreement and inter-system reproducibility with most ICC above 0.80 and relative differences of less than 20% preconceptionally and almost throughout the entire gestational age range. Inter-observer agreement of PVV at 11 weeks gestation was suboptimal (ICC 0.69, relative difference 50.1%). Discussion: Preconceptional and first-trimester 3D PD US utero-placental and fetal vascular volume measurements using VR are feasible and reliable. Longitudinal cohort studies with repeated measurements are needed to further validate these this and assess their value as new imaging markers for placental vascular development and ultimately for the prediction of placenta-related pregnancy complications.