Some pregnant women have severe vomiting, some have only a slight loss of appetite, and some have no reaction at all during the whole pregnancy. What exactly causes early pregnancy reaction? Studies have shown that early pregnancy reaction may be related to the increase of hCG in the mother during pregnancy, insufficient secretion of adrenocorticotropic hormone, disorders of water and sugar metabolism in the body, gastrointestinal dysfunction, reduced secretion of gastric acid and prolonged gastric emptying time. There are also many clinical cases showing that emotional instability, tension, anxiety, depression and insomnia of pregnant women can aggravate pregnancy reactions to a large extent.