ABSTRACT
Objectives:To explore the value of blood oxygen level-dependent (BOLD) MRI in evaluating the changes of placental oxygenation during maternal hyperoxia.Methods:From October 2017 to March 2020, 22 singleton pregnant women with normal placenta showed by ultrasound were prospectively included in Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. Pregnant women wore oxygen mask before examination, and then underwent BOLD MRI examination for 10 min. The pregnant women inhaled air in the first 3 min and continuously inhaled oxygen with purity greater than 90% in the next 7 min (flow rate 12 L/min). The average value of BOLD signal of the whole placenta, fetal side of placenta, maternal side of placenta and maternal kidney were measured and calculated in the first 3 min as before oxygen and the last 3 min of the end of oxygen inhalation as after oxygen. The ΔBOLD was calculated which was the change value of BOLD signal before and after oxygen inhalation. The BOLD values of placenta and maternal kidney before and after oxygen inhalation were compared by using paired t-test. The ΔBOLD of the whole placenta, the fetal side of the placenta and the maternal side of the placenta were compared by using one-way ANOVA, and the LSD method was used for pairwise comparison between groups. Results:There were significant differences in BOLD values of the whole placenta, fetal side of placenta and maternal side of placenta before and after oxygen inhalation ( t=-4.62, P<0.001; t=-4.73, P<0.001; t=-3.57, P=0.002). There was no significant difference in BOLD value of maternal kidney before and after oxygen inhalation ( t=0.35, P=0.740). The ΔBOLD values of the whole placenta, fetal side of placenta and maternal side of placenta were (12.8±2.2)%, (15.1±2.7)% and (6.4±1.3)% respectively. The overall difference was statistically significant ( F=4.49, P=0.015). The results of pairwise comparison showed that there was no significant difference in ΔBOLD between the whole placenta and the fetal side of the placenta ( P=0.450). There were significant differences in ΔBOLD between whole placenta and maternal side of placenta ( P=0.037) and between fetal side and maternal side of placenta ( P=0.005). Conclusion:Under the condition of maternal hyperoxia, the BOLD signal of placenta increased significantly, and the change of fetal side of placenta was more obvious than that of maternal side. BOLD-MRI has the potential of semi-quantitative and real-time evaluation of placental oxygenation.