Purpose or Case Report: Placental insufficiency represents a major challenge in obstetrics, leading to FGR, preeclampsia, and stillbirth. Diagnosis is often delayed until significant fetal compromise has occurred, highlighting an urgent need to develop non-invasive tools for earlier detection. The guinea pig is an ideal translational model, sharing human-like hemomonochorial placentation, but longitudinal assessment remains challenging. We have previously demonstrated the feasibility of terminal CEUS to assess maternal and fetal placental circulation, a critical gap remains in tracking placental changes throughout gestation. The goal of this study was to establish and demonstrate the feasibility of a reproducible protocol for longitudinal multimodal US to characterize the normal temporal evolution of the placenta and its vasculature in a control cohort. This work focuses on acquiring B-mode, Color/Power Doppler, Spectral Doppler, and SWE data across gestation.
Methods & Materials: A pilot study was conducted on 2 healthy, pregnant guinea pigs. Animals were acclimated to handling and imaged while awake and gently handheld, eliminating anesthesia. Longitudinal imaging was performed at 3 distinct gestational time points (GD 45-60). A systematic, quadrant-based anatomical mapping technique was developed to identify and document the location of all placentas. At each of the 3 imaging sessions, 2 specific placentas per dam were targeted for imaging. Standardized settings were used to acquire B-mode, Color, Power, and Spectral Doppler, and SWE data.
Results: The awake imaging protocol was feasible and well-tolerated. Using the quadrant-based technique, we successfully re-identified and imaged the same 2 targeted placentas in each dam across all 3 imaging sessions. High-quality, motion-free cine clips and still images were consistently acquired for all US modalities at each time point from the placenta, umbilical cord, fetal brain, and liver. This confirms our ability to reliably track the development of individual placentas longitudinally without anesthetic confounders.
Conclusions: Reproducible, longitudinal, multimodal ultrasound of the placenta in awake animals is feasible. This protocol successfully overcomes significant challenges of motion and anesthesia. By establishing a reliable method to track individual placental development over time, this work provides the robust, non-invasive foundation required to characterize normal gestational development and, in future studies, identify early quantitative biomarkers in a PI model.