Four-dimensional is also known as four-dimensional ultrasound, four-dimensional ultrasound does not pass may be the examination of the fetal position is not good, the abdominal wall is thicker and so on the reason that some structures do not show clearly, to change the fetal position or let a more professional doctor to check; if it is the fetal organ deformity caused by the pass, need to further do amniocentesis to understand the reason. Generally in the 22 ~ 28 weeks of pregnancy to the hospital to do four-dimensional ultrasound examination, four-dimensional ultrasound examination does not pass may be the examination of the fetal position is not good, can not see certain structures, you can be appropriate to get out of bed activities, eat some food, listen to music, etc. so that the fetus to change the fetal position, and then re-examination of the four-dimensional ultrasound examination. There are some pregnant women who are more obese, the fat of the abdominal wall is thicker will also do four-dimensional ultrasound failed, you can let a more professional doctor to carry out the examination, in order to improve the accuracy rate. Four-dimensional ultrasound does not pass is caused by fetal malformations, need to do further amniocentesis examination, diagnosed with more serious abnormalities, is generally not recommended to continue the pregnancy, try to deal with before 28 weeks of pregnancy. Therefore, if there is any abnormality after pregnancy through the maternity test, you need to consult a doctor in time for examination and treatment.