# Longitudinal 3D‐DCE MRI Assessment of Placental Perfusion Under Reduced Uterine Perfusion Pressure in Pregnant Rats

## TL;DR

This study uses MRI to track changes in placental blood flow in pregnant rats under reduced uterine pressure, finding temporary impairments that recover later in pregnancy.

## Contribution

The first longitudinal use of 3D-DCE MRI in the RUPP model to assess placental perfusion changes over time.

## Key findings

- RUPP caused acute placental perfusion impairments on GD14, including delayed TTP and reduced ME.
- Perfusion deficits in RUPP placentas resolved by GD16–GD18, suggesting placental adaptation over time.
- Voxel-wise analysis showed 20% of RUPP placentas deviated from normal patterns, indicating intralitter variability.

## Abstract

Placental insufficiency is a major cause of preeclampsia and fetal growth restriction. The reduced uterine perfusion pressure (RUPP) rat model reproduces cardinal features of these disorders, but longitudinal changes in placental perfusion after RUPP are poorly documented. This study aimed to assess the acute and late effects of RUPP on placental perfusion between gestational day (GD) 14 and GD18 using 3D dynamic contrast‐enhanced magnetic resonance imaging (3D‐DCE MRI). Pregnant Sprague Dawley rats (n = 31) were randomized to RUPP or normal pregnant (NP) groups on GD14. 3D‐DCE MRI scans were performed on GD14, GD15, and GD16 or GD18. Perfusion parameters, including time to peak (TTP), maximum enhancement (ME), wash‐out percentage (WO%), initial area under the curve (iAUC), and total area under the curve (AUC), were derived from fitted signal–time curves. In addition, exploratory voxel‐wise histogram analysis was performed to assess intralitter variability. At GD14, RUPP placentas showed delayed TTP (p < 0.0001), reduced ME (p = 0.03), reduced WO% (p < 0.0001), and elevated iAUC (p = 0.02). Differences persisted for TTP (p = 0.02) and WO% (p = 0.01) at GD15 but resolved by GD16–GD18. Voxel‐wise analysis revealed intralitter heterogeneity, with 20% of analyzed RUPP placentas deviating from the NP template. These findings indicate that RUPP induces an acute but transient impairment of placental perfusion, with recovery by late gestation. GD14–GD15 emerge as a critical window for detecting acute perfusion impairment and evaluating interventions targeting acute injury.

This first application of longitudinal 3D‐DCE MRI in the RUPP model demonstrated acute perfusion deficits after RUPP that resolved rapidly with advancing gestation, consistent with the adaptive placental responses to reduced uterine blood flow.