OC21.02: Estimation of oxygen saturation, blood flow and blood perfusion in the fetal brain of normally grown fetuses using ultrasound and MRI techniques

To estimate blood oxygen saturation and blood flow in the fetal brain using ultrasound (US) and magnetic resonance imaging (MRI) techniques. Fetal brain venous blood oxygen saturation was calculated in 39 normally grown fetuses using MR susceptometry. Brain blood flow and blood perfusion evaluated by ultrasound and Doppler techniques was measured in 100 normally grown fetuses. All pregnancies were evaluated between 20 and 39 weeks of gestation. Blood flow was calculated in the middle cerebral artery (MCA) by the velocity-time integral (VTI) and vessel diameter (VTI*MCA area) and adjusted by fetal weight (Kg) and by cranial volume (cm3). Intracranial volume was calculated using virtual organ computer-aided analysis (VOCAL). Brain blood perfusion was evaluated in the frontal lobe using power Doppler US and fractional moving blood volume (FMBV) estimation. FMBV expresses the percentage of blood in the studied region. Fetal brain oxygen saturation did not significantly change after 20 weeks of gestation [median: 67.9% (IQR: 64%–74.6%)]. Fetal brain blood flow increased with advancing gestation; however, when adjusted by fetal weight, in remained stable during from 20 to 39 weeks [mean: 52.32 cm3/Kg (IQR: 31.6–71.6)]. The FMBV estimation already represents a percentage in relation to the studied region; therefore, it was not adjusted by fetal weight or cranial volume. The FMBV remained without changes during the study period [median: 23.05% (IQR: 20.4–24.8)]. In normally grown fetuses, brain blood flow, blood perfusion, and venous oxygen saturation did not change after 20 weeks of gestation.