Dry heaving and nausea in early pregnancy are early pregnancy reactions caused by a special hormone, chorionic gonadotropin, or HCG, which is secreted in the body after pregnancy. At the beginning of pregnancy, the corpus luteum becomes the corpus luteum of pregnancy and secretes not only estrogen and progesterone, but also HCG, a special hormone that only occurs during pregnancy, and HCG increases rapidly and doubles. Along with the increase in HCG, some special changes occur in the body of pregnant women, such as an increase in the secretion of gastric acid and a slowing down of gastric motility. Therefore, nausea and vomiting, especially in the morning, and aversion to greasy food, are normal phenomena that most pregnant women can tolerate, and usually appear around 42 days of pregnancy and gradually disappear in the third trimester.