Nausea begins to appear in the first month of pregnancy and is often caused by the following clinical reasons, i. Sensitivity to estrogen, when the estrogen in the body increases slightly, nausea symptoms will appear. Second, twin pregnancy or multiple pregnancy, the body’s estrogen in a short period of time increased dramatically, it will be found in the early nausea, vomiting symptoms. Third, because of abnormal pregnancy, such as in the case of gravida, the body’s estrogen, blood HCG grows rapidly, so very early early pregnancy reaction, manifested in nausea, vomiting, it is recommended to draw blood to check blood HCG, progesterone as early as possible. If the blood HCG is greater than 100,000, it is definitely an abnormality, and it is recommended to do ultrasound to rule out the possibility of hyperemesis gravidarum, as well as to find out whether it is caused by multiple pregnancies.