3D ultrasound is usually done between 22-28 weeks of pregnancy, and the best time is around 24 weeks of pregnancy. At this time, the fetal limbs and major organs have all developed, the amniotic fluid is more suitable, the fetus has more space to move around in the uterus, the echogenicity of the fetal bones is less affected, and the images are clearer, so 3D ultrasound can achieve the best results at this time, and it is easy to obtain the acquisition of facial and tissue organ morphology, which can comprehensively monitor the various developmental indicators of the fetus and check whether the various organs of the fetus are malformed. In addition, it should be noted that nowadays most hospitals require advance booking for 3D ultrasound, so it is best to prepare for this examination and make an appointment in advance to avoid delaying the best time.