The main causes of diarrhea in the first month of pregnancy can be divided into physiological causes and pathological causes. Diarrhea caused by physiological causes can be relieved after adjusting the diet structure, while pathological causes mainly include functional dyspepsia, digestive tract infection, allergic enteritis, etc. Physiological causes: In the early stage of pregnancy, women may experience diarrhea due to the fluctuation of hormones in the body, especially the increase of progesterone level, which will seriously affect the secretion of gastric acid and thus the absorption and utilization of food in the digestive system. Second, the pathological reasons: 1, functional dyspepsia: often caused by poor spirit, improper diet and other factors, pregnant women often do not have organic lesions in the digestive system, manifested as occasional diarrhea, with or without pain in the abdomen, the symptoms usually do not last. The symptoms will be relieved if the pregnant woman consumes less or no spicy or cold food and keeps her mood soothed. If the symptoms have a tendency to aggravate, they can be treated with oral drugs such as cimetidine and ranitidine to inhibit gastric acid secretion under the guidance of a doctor; 2. Digestive tract infection: usually caused by unclean diet or lack of hygiene, manifested as more violent diarrhea, accompanied by pain in the abdomen and vomiting. Pregnant women should usually pay attention to hand hygiene before and after meals, choose fresh ingredients, do not eat overnight meals, and use antibiotics under the guidance of a doctor when diarrhea is serious; 3, allergic enteritis: generally caused by pregnant women due to the consumption or oral allergy-causing foods and drugs, in addition to diarrhea, patients may also be accompanied by abdominal pain, nausea, vomiting, high fever and other symptoms. If the disease recurs, it is easy to lead to acid-base imbalance in the body, and in serious cases, patients may experience fluid loss shock. It is recommended to seek medical attention in a timely manner, and the treatment starts with removing allergic factors, and the diet is light and easy to digest. Patients can be treated with oral antidiarrheal drugs such as loperamide and compound diphenoxylate. In addition, there are some diseases such as lymphoma, intestinal cancer, aspirin disease, chronic gastritis, etc. may cause diarrhea in the first month of pregnancy, and may be accompanied by other symptoms. The diarrhea caused by diseases should be treated first for the original disease before the diarrhea can be relieved, and the cause can be identified first for further treatment.