Currently, ultrasound is the most intuitive, quick and safe way to test a fetus for malformations or lesions. In the eyes of most people, as long as the ultrasound does not find any problems, then it is logical that a healthy baby should be born. However, it is not the case that regular ultrasound examinations still give birth to deformed babies. The main purpose of ultrasound during pregnancy is to understand the condition of the baby and its appendages in the womb, such as whether the size of the baby matches the gestational week, how the amniotic fluid, placenta and fetal position are ……, and secondly, to observe whether there are obvious deformities in the baby at the right time so that appropriate measures can be taken to reduce the rate of neonatal defects. Some mothers always ask their doctors again and again, “Is the baby normal?” To be honest, this is a question that causes doctors a lot of headaches. First of all, the word normal itself contains a lot of meanings, including not only structural normal but also functional normal. Through ultrasound examination, doctors can see that the fetus has eyes, but it is not clear whether the eyes are beautiful or whether the vision is normal. To use an analogy, it is a normal looking child in front of him, he just stays quiet, no one can judge whether his vision or hearing is normal, let alone across the mother’s belly. Secondly, ultrasound examination can only detect 60% to 80% of congenital abnormalities of the fetus, and the ultrasound examination is influenced by many factors such as the position of the fetus, the amount of amniotic fluid, the weight of the mother, and even the experience of the doctor, plus the examination is not continuous, so some abnormalities may not be accurately detected. For example, if the fetus is always facing the mother when doing the examination and the back is facing the probe, the doctor has no way to see the fetus’ face; if the fetus’ fist is clenched, the doctor cannot see the condition of the fetus’ hand. The fetus is constantly growing and changing, and even if there are no abnormal organs in the early examination, there is no guarantee that they will be normal after birth. Therefore, ultrasound is only a reconnaissance and not a prediction, and one should not place 100% hope on it. According to the requirements of the State Ministry of Health, only the following six serious malformations must be detected by ultrasound: first, anencephaly, second, lethal chondrodysplasia, third, thoracoabdominal wall defect visceral exostosis, fourth, single-chambered heart, fifth, open spina bifida, and sixth, brain expansion. In other words, hospitals are exempted from liability as long as the child born is not one of these six malformations. So when mothers-to-be want a positive assurance from their doctors, they often can only reply that in front of them, within the observable range, no obvious structural abnormalities were found. This means that this is only the result of the present examination and it does not predict or guarantee that the condition of the fetus will not change in the next moment, and it is only for the part that can be seen now, and there is no guarantee for the part that is not seen because of the fetal position and other factors. In addition to verbal communication, some languages add a paragraph at the bottom of the ultrasound declaration that in most cases, fetal ear, eye contents, fingers, toes and soft tissue abnormalities do not fit into the display. Regardless of the method used and the stage of pregnancy, it is unrealistic and unreasonable to expect to detect all fetal anomalies, even if the most renowned specialists are allowed to perform a thorough examination.