4D ultrasound is a very important examination item in prenatal examination, which is usually performed around 24-28 weeks of pregnancy. The fetus is more mature and its internal organs and tissues are well developed around 24-28 weeks of pregnancy, and the amniotic fluid is not too much, so the fetus’ limbs can be freely stretched in the amniotic fluid during the 4D ultrasound examination to reduce the local masking, so that the growth and development of the fetus can be understood more clearly and distinctly. If the limbs are covered or the fetal extension is limited during the examination, regular follow-up examinations should be performed, and the timing of the review should be chosen according to the specific condition of the fetus and the amniotic fluid. In addition, since 4D ultrasound examinations take longer than ordinary ultrasound and are more demanding on the examiner, it is usually necessary to make an appointment for 4D ultrasound in advance. If there are any abnormalities in the 4D ultrasound results, you can visit the Eugenics and Genetics Department for prenatal consultation.