In-vivo MRI-based assessment of placental morphology in growth-restricted fetuses

Placental insufficiency is a major cause of fetal growth restriction (FGR), yet current in-vivo imaging methods for placental assessment are limited. MRI-based placental biomarkers may provide a promising tool to identify fetuses at risk. This study aims to evaluate placental morphology using in-vivo MRI in third-trimester fetuses, identify structural features associated with gestational-age (GA) and growth outcomes, and identify features that differentiate appropriate-for-GA (AGA) from FGR-complicated fetuses.

A total of 141 participants (102 AGA and 39 FGR due to placental insufficiency) were scanned between 30 + 0 and 37 + 2 weeks of gestation using 3T MRI True Fast Imaging with Steady-State Free Precession sequence. Seventeen morphological features were extracted, including umbilical cord insertion location, quantified as the centricity index (CI), placental volume, shape, maternal and fetal surface areas, along with fetal body and birthweight measures. Inter-observer agreement for CI was assessed with Intraclass correlation. Associations between placental morphology, GA, and growth outcomes were evaluated using Spearman's correlation. Group differences were tested with Mann-Whitney U and Benjamini-Hochberg correction (p < 0.05).

In AGA, placental elongation increased with GA (r = -0.238). Placental volume, minor axis length, maximum 2D diameter, and surface areas correlated with growth outcomes (r = 0.21-0.40). In FGR, placental volume and surface areas were correlated with GA (r = 0.32-0.38). Placental volume remained associated with growth outcomes, and CI with birthweight percentiles (r = 0.34-0.60). FGR placentas exhibited marginal cord insertions, smaller size measures, and higher surface-to-volume ratio.

MRI-derived placental morphology shows alterations in FGR and associations with growth outcomes, supporting identification of at-risk fetuses.