Early pregnancy reaction is usually most serious at 8 to 10 weeks of pregnancy. The appearance of early pregnancy reaction is related to the rise of HCG level in the pregnant woman’s body, which usually begins to appear around 6 weeks of pregnancy, and then gradually aggravates and maintains for a period of time and then relieves. HCG in the pregnant woman’s body can generally be measured 7~8 days after fertilization, and reaches the peak at 8~10 weeks of pregnancy, so the early pregnancy reaction is most serious at 8~10 weeks of pregnancy. After 8~10 weeks, the level of HCG decreases rapidly and stays at a lower level, and the pregnancy reaction also decreases. In addition, pregnant women who are overly nervous, anxious, emotionally worried, or living in a poor environment are also prone to noticeable early pregnancy reactions or even severe vomiting. If early pregnancy reaction occurs, it is recommended to go to the hospital in time and follow the doctor’s advice to deal with the treatment.