Is it three-dimensional or four-dimensional?

Large row abnormality examination, generally refers to 20-22 weeks, when the row abnormality examination, in fact, is small row abnormality. 26 to 28 weeks to do four-dimensional color Doppler ultrasound is large row abnormality examination. Usually said large row abnormality, in fact, small row abnormality examination, this row abnormality examination is a three-level examination, not three-dimensional color Doppler ultrasound and four-dimensional color Doppler ultrasound, is three-level ultrasound examination, is what the common people call large row abnormality. 4-D ultrasound examination at 26 - 28 weeks is actually a large row of abnormal examination, 3-D and 4-D is a static and a dynamic examination. Therefore, 3-D and 4-D ultrasound examination is performed at 26-28 weeks, and 20-22 weeks of abnormal examination is a tertiary ultrasound examination.