Xiao Wang was 5 months pregnant and found that the fetal ventricle was enlarged during an ultrasound examination at the hospital, and the doctor recommended that she have an MRI to further confirm the diagnosis. She was worried that the MRI would adversely affect the development of the fetus and refused to do it, but regretted that she was born with anencephaly. In clinical work, we often encounter some pregnant women who come to consult with us, saying that my baby’s ultrasound examination reveals abnormalities, and it is said that MRI can see more clearly and further confirm whether it is possible to do MRI examination. In fact, Wang’s worry is superfluous, because MRI is different from fluoroscopy and CT examination, it does not use X-rays, but uses the signal generated by the resonance of specific atomic nuclei (mainly human hydrogen protons) in the magnetic field to obtain images, so there is no ionizing radiation, and it is a non-invasive and safe examination method. It has been more than 20 years since MRI was first reported for fetal examination in 1983, and the harmful effects on the fetus and its development have not yet been reported. However, most scholars believe that fetal MRI in the first trimester of pregnancy should be performed with caution because it is a period of embryonic formation and development when external stimuli and disturbances should be avoided as much as possible. Therefore, fetal MRI should be performed in the third trimester and without sedative drugs or contrast agents as an important complement to ultrasonography for prenatal examination.