ORIGINAL RESEARCH Fetal Response to a Maternal Internal Auditory Stimulus Estee Goldberg, BSc, 1 Charles A. McKenzie, PhD, 1,2,3 Barbra de Vrijer, MD, 3,4 Roy Eagleson, PhD, 1,5 and Sandrine de Ribaupierre, MSc, MD 1,2,3,5,6 * Background: Functional MRI (fMRI) is a noninvasive method to investigate the neural correlates of brain development. Insight into the rapidly developing brain in utero is limited, and fetal fMRI can be used to gain a greater understanding of the developmental process. Fetal brain fMRI is typically limited to resting-state fMRI due to the difficulty to instruct or pro- vide a stimulus to the fetus. Previous studies have employed auditory task fMRI with an external sound stimulus directly on the abdomen of the mother; however, this practice has since been deemed unsafe for the developing fetus. Purpose: To investigate a reliable and safe paradigm to study the development of fetal brain networks, we postulated that an internal task, such as the mother’s singing, as the auditory stimulus would result in activation in the fetal primary audi- tory cortex. Study type: Cohort. Population: Pregnant women with singleton pregnancies (n = 9; 33–38 weeks gestational age). Field Strength/Sequence: All subjects underwent two task-based block design blood oxygen level-dependent (BOLD) at 1.5T or 3T. Assessment: Each volume was assessed for fetal motion and manually reoriented and realigned to correct for fetal motion. Once the motion was corrected, a gestational age-matched parcellated atlas with regions of interest overlaid onto the activation map was used to determine which regions in the brain had activation during task phases. Statistical Tests: First Level Analysis. MRI data were analyzed using SPM 12 as a task fMRI. Results: Eight subjects had activation on the right Heschl’s gyrus; six fetuses demonstrated activation on the left when exposed to the internal acoustic stimulus. Additionally, activation was found on the right and left middle cingulate cortex (MCC) and the left putamen. Data Conclusion: Maternal singing can be used as an internal stimulus to activate the auditory network and Heschl’s gyrus during fetal fMRI. Level of Evidence: 2 Technical Efficacy Stage: 2 J. MAGN. RESON. IMAGING 2020. I nsight into the rapidly developing fetal brain is scarce; thus, recent studies have used fetal functional magnetic resonance imaging (fMRI) as a technique to assess fetal brain activity. 1,2 Imaging and assessment of functional norms in utero are challenging due to random fetal and maternal motion, mater- nal respiration, the small fetal brain, the high water content in the fetal brain compared to the adult, and the fact that the head of the fetus is deep within the mother, far away from the receive coils. In traditional adult task-based fMRI, the participant is instructed with a task to complete; however, fetal brain fMRI is often limited to resting-state or nonstimulus-based fMRI due to the difficulty to instruct or provide a stimulus for the fetus. The fetal brain rapidly develops and grows in utero, undergoing substantial structural and functional changes throughout pregnancy. 3 Auditory development begins struc- turally around 15 weeks gestational age (GA) and is func- tional by 20 weeks GA. At around 25 weeks GA the auditory system becomes functional as the ganglion cells of the spiral nucleus in the cochlea connect the inner hair cells to the View this article online at wileyonlinelibrary.com. DOI: 10.1002/jmri.27033 Received Oct 21, 2019, Accepted for publication Dec 11, 2019. **Address reprint requests to: S.R., Victoria Hospital, B1-181, 800 Commissioners Rd E, London, ON N6A 5W9, Canada. E-mail: sderibau@uwo.ca From the 1 Biomedical Engineering, Western University, London, Ontario, Canada; 2 Medical Biophysics, Western University, London, Ontario, Canada; 3 Children’s Health Research Institute, Western University, London, Ontario, Canada; 4 Department of Obstetrics and Gynaecology, Western University, London, Ontario, Canada; 5 Brain and Mind Institute, Professor of Engineering, Western University, London, Ontario, Canada; and 6 Department of Clinical Neurological Sciences, Western University, London, Ontario, Canada © 2020 International Society for Magnetic Resonance in Medicine 1