Placental T2* and BOLD effect in response to hyperoxia in normal and fetal growth restricted pregnancies : multicenter cohort

Abstract

ABSTRACTObjectivesBlood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (f‐MRI) technique allows a non‐invasive in‐vivo evaluation of placental oxygenation. The aim of this study was to highlight and quantify a relative BOLD effect in response to hyperoxia in the human placenta and to compare it between FGR and non‐FGR fetuses (fetal growth restricted).MethodsIn a prospective multicenter study (NCT02238301), we included 19 FGR fetuses (cases defined by an ultrasound‐based estimated fetal weight (EFW) <5th centile) and 75 non‐FGR fetuses (controls). Using a 1.5 Tesla MRI system, the same multi‐echo gradient recalled echo (GRE) sequences were performed at both centers to obtain: placental T2* values in baseline and in hyperoxic conditions and the relative BOLD effect according to the following equation: Relative BOLD effect = 100 x (hyperoxicT2*‐baseline T2*)/baseline T2*. The baseline T2* values and relative BOLD effect were compared according to fetal weight estimations (between FGR and non‐FGR fetuses), presence of Doppler anomalies and according to birth weight (between appropriate and small for gestational age newborns – AGA/SGA).ResultsWe demonstrate a relative BOLD effect in response to hyperoxia in the human placenta, quantified at 33.8% (22.5;48.0). The relative BOLD effect was not statistically different between FGR and non‐FGR fetuses (34.4% (26.1‐33.4) versus 33.7% (22.7‐139.2), p=0.95). Baseline T2* values Z‐score adjusted for gestational age at MRI ​​were significantly lower for FGR fetuses as compared with non‐FGR fetuses (‐1.27 (‐4.87;‐0.10) vs 0.33 (‐0.81;1.02) respectively, p=0.001). Baseline T2* values Z‐score were also significantly lower for the subsequently SGA neonates (‐0.75 (‐3.48; 0.29 n=23) vs 0.35 (‐0.79;‐1.05 n=62), p=0.01).ConclusionsOur study confirms a BOLD effect in the human placenta and that baseline T2* values are significantly lower in FGR fetuses. Further studies are needed to evaluate whether such parameters may detect placental insufficiency, before it has a clinical impact on fetal growth.This article is protected by copyright. All rights reserved.