Causes of hyperemesis gravidarum: First, nutritional factors. Staphylococcus is mostly found in rice-eating countries and is therefore thought to be related to nutrition. It has been found that patients with gestational trophoblastic tumors have low serum folic acid activity, and a lack of folic acid during the period of embryonic angiogenesis affects the synthesis of thymine, which leads to embryonic death and a lack of blood vessels in the placental villi. The second, infectious factor. Many people believe that hyperemesis gravidarum is associated with viral infections, but have failed to identify real evidence. Third, endocrine disorders. It is believed that the development of hyperemesis gravidarum is associated with ovarian insufficiency or decline, and is most common in women under 20 years of age as well as in women over 40 years of age. Fourth, defects in the pregnant egg. This may be related to abnormalities in the development of the egg itself. There is also a relationship with race, and differences in the incidence of hyperemesis gravidarum between races have been noted. The last one is overexpression of proto-oncogenes and inactivation of hetero-oncogenes. The activation and overexpression of proto-oncogenes and the mutation and inactivation of hetero-oncogenes are genes that control the growth and differentiation of cells, and they are related to the development of tumors.