In Vivo Assessment of Placental Structure and Perfusion in Late‐Gestation Pregnancies and Their Association With Fetal Growth

ABSTRACT

Adequate placental structure and function are crucial for fetal growth, while placental dysfunction often leads to fetal growth restriction (FGR), associated with increased perinatal morbidity and mortality. Current FGR criteria, relying on sonographic biometry and Doppler assessments, typically fall short in sensitivity for diagnosing FGR, predicting perinatal outcomes, and assessing their association with placental pathology. Advanced MRI methods offer a unique opportunity to characterize placental structure and perfusion, and to assess their relationship with fetal growth. This study aims to provide normative quantitative MRI values of placental structure and perfusion during the third trimester, to assess their interplay and association with fetal growth, and to identify differences between appropriate‐for‐gestational‐age (AGA) and FGR‐complicated pregnancies. With IRB approval, pregnant women between 30 and 37 weeks of gestation (AGA [ n  = 46], FGR [ n  = 11]) underwent prospective MRI. Placental structure (volume; umbilical‐cord centricity‐index [CI]), placental perfusion (placental‐blood‐flow [PBF] and arterial‐transit‐time [ATT] extracted from arterial‐spin‐labeling), fetal growth (estimated body weight and brain volume), and radiomics features derived from PBF and ATT maps were assessed using deep‐learning and image‐processing tools. Statistical analyses included Pearson correlation, analysis of covariance with gestational‐age (GA) as a covariate, non‐parametric tests, logistic regression, multistep feature selection, and false discovery rate correction. Fetal growth parameters correlated with GA in both groups and were significantly reduced in FGR. Mean perfusion values of AGA placentas were significantly higher than previously reported at earlier GA using the same method. Placental volume correlated with ATT and total placental flow (mean PBF × placental volume/100) in AGA fetuses. Total placental flow was significantly lower in FGR compared with AGA. CI and two ATT radiomics features contributed most to differentiating AGA from FGR, with higher CI in FGR. Our findings highlight CI as a potential marker for growth restriction. Larger studies are needed to better characterize perfusion alterations in FGR.