Women who are pregnant are perhaps the most cautious people in the world. To prevent radiation damage, pregnant women are on high alert, and they are even afraid to use their cell phones, so will ultrasound have an effect on the fetus? I. What is ultrasound The so-called ultrasound is a sound wave with a frequency greater than 20 kilohertz, which cannot be heard by the human ear. Since it is a sound wave, it will carry a certain amount of energy, describing the physical quantity of ultrasound energy is the sound intensity, the unit is watts per square centimeter. The greater the sound intensity, the greater the energy of ultrasound, the greater the effect that can be produced on living organisms. Second, ultrasound damage to the human body in the known ultrasound injury, can be broadly divided into three categories: 1, heating ultrasound is with energy, absorbed by the body’s cells, it can be converted into heat, resulting in a local cell temperature rise. It can be said that this temperature change is generally small and slow, but some of the human tissue is not heat-resistant, such as testicular tissue and embryos, if a long time or a large dose of exposure to ultrasound, whether it is a “small slow cook” or “rapid frying “, are likely to damage these fragile tissues. 2, vibration General medical ultrasound frequency are in between 2 MHz to 10 MHz, that is, two million to 10 million times per second vibration. Such a high frequency of vibration can cause the connection between the cells to loosen, causing damage to the tissue. If the amplitude of the vibration is large, the strength of the cell membrane can not withstand, or even tear the cells. 3, “cavitation effect” ultrasound can also produce a very special effect on the organism, called the “cavitation effect”. That is, the high-frequency vibration of ultrasound will cause the shocked liquid to produce tiny bubbles invisible to the naked eye, these bubbles are squeezed by sound waves, will instantly shrink and then burst, while releasing a large amount of energy, instantly can reach thousands of degrees of heat, causing burns to the surrounding tissue. The impact of ultrasound on pregnant women and fetuses Regarding the impact of ultrasound on pregnant women and fetuses, in fact, as early as the 1960s, the medical profession has reached a consensus that the ultrasound intensity used as a diagnostic, even if repeatedly irradiating the embryo in the pregnant woman, will not produce abnormal embryonic development. Follow-up of children who had received ultrasound in the mother’s body also showed that ultrasound did not affect the physical or mental development of the fetus after birth. However, ultrasound examinations of pregnant women who are sensitive to external influences within the third month of pregnancy are still subject to strict limitations, and the duration of the operation is required to be controlled within 5-10 minutes to avoid possible and potential damage to the embryo as much as possible. After the third month of pregnancy, the fetal resistance is relatively strong, so you can relax a little, but still pay attention to the duration of the examination, it is best to keep it as short as possible. If a pregnant woman does ultrasound exams on her fetus too frequently and too much in the early stages of pregnancy, or even takes ultrasound videos of her fetus, there is no guarantee that it is absolutely safe for the fetus. Even if the damage caused by vibration and cavitation effects can be disregarded at lower sound intensities, the tissues exposed to ultrasound for a long time will warm up due to the heating effect, thus increasing the risk of fetal injury. However, if a standard ultrasound examination is performed under the guidance of a physician, the possibility of harm to the mother-to-be and the fetus is negligible.