The most common cause of vague pain on the left side of the stomach in the third trimester is gastrointestinal tract dysfunction of pregnant women, failure to ventilate and defecate in a timely manner, left intestinal distension, causing discomfort. You need to adjust your diet, maintain water intake, eat more vegetables and fruits, and have bowel movements on time, which are physiological discomfort and do not cause excessive worry, while observing the changes in the condition. If the fetus and the uterus increase in size as the months go by, upward and forward pressure on the gastrointestinal tract and bladder will cause gastrointestinal tract and bladder dysfunction, serious pain and a long course of illness, it should be noted. If the pregnant woman also has vaginal bleeding, the possibility of pre-eclampsia miscarriage cannot be excluded. Pregnant women who eat spicy, stimulating and cold food, causing gastrointestinal disorders, enteritis and intestinal spasm, need symptomatic treatment. If it is said that the pain in the right lower abdomen is more serious, accompanied by fever, nausea and vomiting, the possibility of acute appendicitis cannot be ruled out, and timely medical consultation and treatment are needed to avoid unnecessary complications.