It is often said that “a baby is conceived in October and delivered at the same time”, which shows that pregnancy is a long process. In the long process of October pregnancy, many mothers-to-be have the mood of joyful anticipation, but also often accompanied by a little restlessness and even anxiety. Why? Because some pregnant women during pregnancy or in the very early stages of pregnancy (pregnant women did not know they were pregnant) due to some diseases, in the process of diagnosis and treatment of diseases, such as ultrasound, X-ray, CT or MRI and other imaging examinations, mothers-to-be and their families are often very concerned about and worried about the safety of these tests on the fetus. So, can these tests be performed during pregnancy? Is there any adverse effect on the baby in the abdomen? 1, ultrasound: ultrasound has become a necessary means of diagnosis of many diseases, but also a necessary tool to check the fetus, at present in the obstetrics and gynecology community has reached a consensus that ultrasound during pregnancy, including Doppler examination of the fetus is safe, and should be as far as possible to replace the X-ray examination as the preferred method of fetal imaging. 2, X-ray examination: Clinical often encountered some women before the diagnosis of pregnancy, for some reasons (such as physical examination, etc.), has been done X-ray examination, and some other women due to pregnancy suffering from certain diseases need to X-ray examination to diagnose the disease, so how to objectively evaluate the necessity of X-ray examination and the pros and cons of it? X-ray examination of the impact on the fetus and the amount of radiation and timing of exposure to the X-ray is related to. Large doses of X-ray radiation may cause miscarriages, malformations, etc. However, the absorbed dose of the body for medical radiation examination is extremely low, and a single X-ray film examination before 2 weeks after fertilization or after 20 weeks will not cause damage to the fetus. Therefore, in 2 to 20 weeks after fertilization, non-essential X-ray examination should be cautious or postponed. 3, nuclear magnetic resonance examination: At present, the effect of nuclear magnetic resonance examination on the fetus is not clear, although there have been animal studies show that pregnant rats in the 9th day of pregnancy exposure to 4 dessler (dose unit) magnetic field for 9 hours on the development of the fetus has no effect on the rats, there are still a few studies believe that exposure to the magnetic field of the nuclear magnetic resonance examination in early pregnancy may have a teratogenic effect on the fetus of the animal. Therefore, this test should still be performed with caution during early pregnancy and should only be used in women during early pregnancy if it is relevant to decision-making about the management of the disease.