The purpose of the examination is to find out whether the baby’s organs are developing normally and to rule out malformations of the body and major organs. This is the best time for the examination because the baby’s organs have developed and reached a certain size, and the amniotic fluid volume is also sufficient. If the gestational week is bigger, the amniotic fluid volume of the pregnant woman will decrease, the fetal position will be fixed, and some parts of the organs may not be examined due to the restricted position, so the ultrasound examination will take longer time. 4D color ultrasound is a systematic ultrasound examination, and it belongs to the third level of ultrasound in obstetrics department, and generally some hospitals need to make an appointment in advance for 4D color ultrasound. The 4D ultrasound is an important and mandatory checkup in the middle of pregnancy, and it is recommended to have a routine checkup after pregnancy.