Myth 1: Is it three-dimensional or four-dimensional? In fact, real-time 3D is 4D, which is a 3D image with a timeline, showing a three-dimensional image that changes with time. Myth 2: The bigger the fetus is, the clearer the examination is. For example, the best time for examination of limb malformation is around 20 weeks (i.e. 18-22 weeks). For example, the best time to examine limb anomalies is around 20 weeks (i.e., 18-22 weeks), because as the fetal weeks increase, the fetal body enlarges significantly faster than the growth of the uterine volume, so the range of motion of the fetal limbs in the uterus will be correspondingly smaller, resulting in the inability to flex and extend the limbs in the uterus, which limits the examination of limb anomalies and development. Some pregnant women usually wait until they are more than thirty weeks or even full term to have an ultrasound examination, thinking that the bigger the fetus the clearer the ultrasound examination, which is precisely wrong. Myth 3: Why can other people’s babies be photographed, but not mine? The best time to take fetal facial photos is around 20-28 weeks. The effect of fetal facial photos is directly affected by several factors, such as: 1. The fetal gestational week is too small or too large. If the fetal gestational week is too small, the fetal facial muscles are not well developed, and the shooting effect is not very beautiful; if the fetal gestational week is too large, although the facial muscles are full, but the range of movement of the fetal head is limited, for example, the fetal face is facing the mother, the fetal head is too much upward or too much downward and other situations will cause the shooting of photos more difficult or can not be shot. 2, the fetal position and the amount of amniotic fluid in front of the area. If the fetal position is not suitable for photographing or the amount of amniotic fluid in front of the area is too small or no amniotic fluid, it is not possible to take photos of the fetal face. Myth 4: The purpose of doing 4D ultrasound is to take pictures, if I don’t take them, won’t my money be wasted? The so-called “four-dimensional” ultrasound is a real-time dynamic three-dimensional color ultrasound imaging technology that combines the three-dimensional spatial structure of “length, width and height” with the concept of “time”. The real use of this technology is to check whether there are deformities in the fetal structure and what deformities exist, so as to improve eugenics, not to be a “4D ultrasound camera” that is specially designed to take pictures of the fetus. Myth 5: If no abnormality is found in the 4D ultrasound examination, you can rest easy. The superiority of 4D ultrasound lies in its high resolution, clear imaging, and the ability to reconstruct three-dimensional images, but it has its blind spots, just like general ultrasound instruments. It is limited by the small size of the lesion, fetal position, amniotic fluid volume, fetal posture, and the similarity of image performance of different lesions, so the ultrasound examination results must be combined with clinical practice before a diagnosis can be made. At the same time, things are changing and developing, and just because an abnormality is not detected in one ultrasound examination does not mean that there will be no abnormality in the future. Therefore, we sometimes ask patients to have regular checkups. Myth 6: Taking 4D ultrasound is just like watching color TV. Many pregnant women ask “why is it not in color” when they first start the 4D ultrasound examination. In fact, the color ultrasound is not the real color of human tissue, but the pseudo-color based on the principle of Doppler effect on top of the black and white ultrasound image. So what is the Doppler effect, when we stand on the train platform to listen to the train whistle from a distance will be higher than the train whistle away from us, that is to say, for the stationary observer, towards the observer movement of the object issued by the frequency of sound waves will rise, the opposite frequency will be reduced, this is the famous Doppler effect. Modern medical ultrasound is the use of this effect, when the ultrasound encounter flow away from the probe liquid echo frequency will be reduced, the flow of liquid to the probe will make the probe receive the echo signal frequency increase. This is described using computerized pseudo-color technology, which allows us to determine the direction of the flowing fluid in the ultrasound image and the size and nature of the flow rate, and to superimpose this on the two-dimensional black and white ultrasound image, forming the color ultrasound image we see today. When you see red or blue blood flow signals, don’t mistake red for arterial blood and blue for venous blood. In fact, red only means that the blood is flowing towards the probe and blue means that the blood is flowing back towards the probe.