MRI-Based Quantitative Analysis of Placenta and Fetal Brain in Small-for-Gestational-Age Pregnancies: A Feasibility Study

Background: Small-for-gestational-age (SGA) pregnancy is often associated with impaired placental function, which would lead to neurodevelopmental deficits. Objective: To utilize the geometric properties of cortical development for quantitative analysis of the relationship between impaired placental function and fetal brain development in pregnancies with small-for-gestational-age (SGA) fetuses. Materials and methods: This retrospective study included 41 pregnant women with appropriate gestational age (range: 23-38.6 weeks) and 26 pregnant women with SGA pregnancies (range: 23.3-36.3 weeks). After the exclusion of 25 participants with normal fetal brain data but noticeable motor artifacts, 29 fetal brains from the normal group and 16 fetal brains from the SGA group were included in this analysis. Examinations were conducted using a 1.5 T magnetic resonance imaging system. Fetal brain cortical thickness and regional volume were calculated for each participant, according to a standardized anatomical atlas. Placental intravoxel incoherent motion (IVIM) imaging and T2* mapping were performed. IVIM parameters (perfusion fraction [FP], perfusion diffusivity coefficient [DP], and tissue diffusivity [D]) and T2* parameters were subsequently analyzed. Results: FP and T2* values were significantly lower in SGA pregnancies than in the control group (p<0.05), indicating impaired placental growth. Nine regions of cortical thickness exhibited significant differences (p<0.05) between the normal and the SGA groups. In the control group, 30 of 86 brain regions (34.88%) exhibited moderate or strong correlations between cortical thickness and T2* values. Among these regions, 19 were in the right hemisphere, whereas 11 were in the left hemisphere. Conclusion: Quantitative assessment of changes in placental function and fetal brain cortical thickness is feasible and may provide valuable pathophysiological insights.