Pregnancy reaction is clinically called early pregnancy reaction, which can occur after pregnancy due to the change of hormone level in women’s body, such as cold, dizziness, weakness of limbs, drowsiness, nausea and vomiting, dislike of greasy and sour food, etc. It is a normal phenomenon and mostly occurs about 6 weeks after menopause. The reaction can be mild or severe depending on individual’s physical quality, and in serious cases, it is said to be a big reaction to pregnancy. Usually, early pregnancy reactions usually have little impact on life and work and do not require special treatment, and disappear naturally around the 12th week of pregnancy. The specific cause of severe pregnancy reaction is not clear, but may be mainly related to hormonal effects in the body, such as chorionic gonadotropin (hCG), as well as mental state and social factors. However, the severity of vomiting is not proportional to the hCG level. In addition, pregnant women with fear of pregnancy, emotional instability, low social status and poor economic conditions are more likely to have severe pregnancy vomiting; severe pregnancy vomiting is also associated with unclean diet, H. pylori infection, female embryos and low pre-pregnancy weight. In conclusion, the high pregnancy reaction may be related to various factors such as blood hCG, maternal mental factors and social factors. In addition, severe pregnancy vomiting mostly occurs between early pregnancy and 16 weeks of gestation, with frequent nausea and vomiting as the main cause. If the vomiting is severe, it may prevent you from eating and lead to severe weight loss, electrolyte disorders, acid-base imbalance, ketosis, liver and kidney failure, which may affect the growth and development of the fetus and may be life-threatening in serious cases.