At 12 weeks of pregnancy, you can only do ultrasound, and you need to follow the doctor’s instructions. Ultrasound is the use of high-frequency sound waves to clearly display the internal tissues of the human body, organs, cross-sectional images, images rich in solid sense, easy to observe the morphology of tissues, can be used for early pregnancy examination, there is no radiation, safer, 12 weeks of pregnancy can be only ultrasound examination. The ultrasound examination can determine the number of days of pregnancy and provide a reliable basis for the expected date of delivery. At the same time, depending on the period of ultrasound examination, it can also clarify whether the pregnancy is normal or not, and know whether there is any abnormality in the development of the fetus in the uterus. In early pregnancy, ultrasound can check the thickness of the neck of the fetus and determine whether there are any abnormalities in the fetus. In mid-pregnancy, ultrasound can provide a more comprehensive examination of the fetus and detect serious structural abnormalities in a timely manner. Ultrasound examination in late pregnancy can be performed to find out whether the developmental rate of the fetus is consistent with the pregnancy cycle, whether the amniotic fluid volume is normal, whether there is intrauterine hypoxia and the position of the placenta attachment. Pregnant women who feel unwell should go to the hospital in time.