Ultrasound is an intermittent pulsed emission with an average power of 30 to 40 milliwatts/cm2 or less. It does not have the same radiation and biological effects as X-rays, so in general it is not so harmful to the pregnant woman or the fetus. Foreign scholars have conducted ultrasound examinations on 720 pregnant women over 12 weeks for 5 to 15 minutes, and did not find any maternal and fetal operation damage. But in recent years, there are also medical workers put forward a different point of view, such as in 1994, the University of Cali, Canada’s Can ultrasound is an intermittent pulse emission, the average power of 30 to 40 milliwatts / cm2 or less. It does not have radiation and biological effects like X-rays, so in general, it does not cause harm to pregnant women or fetuses. Foreign scholars have conducted ultrasound examinations on 720 pregnant women over 12 weeks for 5-15 minutes, and did not find any maternal and fetal operation damage. However, in recent years, there are also medical practitioners to put forward a different point of view, such as the University of Cali, Canada in 1994. Color multispectral ultrasound is based on B-type ultrasound increased blood flow display and measurement functions, some hospitals introduced three-dimensional ultrasound and fetal heart examination software, etc. can better prenatal understanding of the fetal face and umbilical blood flow, fetal heart condition, etc., which can increase the detection rate of fetal malformations, increasing the safety factor for the birth of a healthy baby. But ultrasound has no effect on the fetus examination is a question many parents want to know. Ultrasound is a sound wave with a frequency of 20,000 Hz or more, which is inaudible to the human ear. The principle of ultrasound instrument is based on the different densities of various tissues and organs, and the sound waves enter the body to produce different reflections, refraction, absorption and attenuation, and the reflected waves can be displayed on the ultrasound instrument through the internal organ images of the human body, therefore, it belongs to a physical examination method. Its emission method is intermittent pulse emission. Ultrasound has been used in clinical practice for nearly forty years, and its safety has been confirmed. Theoretically, high-intensity ultrasound may cause damage to tissues through its high temperature and cavitation of tissues, but it is used in medicine at low intensity with an average power of 30-40 milliwatts/cm2 or less, so it does not have radiation and biological effects like X-rays, and generally does not cause harm to pregnant women and fetuses. Since it is safe, easy and non-invasive, it can be repeatedly examined many times and until now there have been no reports of causing fetal malformations and tissue damage.