MRI has no effect on an 8-month-old baby. MRI is relatively safe compared to other imaging methods because it uses the nucleus of hydrogen atoms moving under the action of an applied magnetic field to perform imaging, so there are no reports of MRI being harmful to humans in the world so far. For younger children, doctors try to avoid radiation-based imaging methods and opt for MRI or ultrasound instead. However, MRI has high requirements for patients, for example, babies as young as 8 months old cannot cooperate with the doctor, so they are usually sedated before the examination, and very few children may have allergic reactions to sedative medications.