The vague pain in the stomach in the third trimester of pregnancy should be taken seriously and may be caused by the following reasons: 1. physiological abdominal pain, because the third trimester of pregnancy is in the early stage of pregnancy, the development of the embryo is still unstable at this time, the estrogen in the pregnant woman’s body is increasing, the uterine ligament has a pulling sensation, resulting in abdominal pain, which will be relieved after rest; 2. pathological abdominal pain, if the pregnant woman does not pay attention to the health of the diet in the early stage of pregnancy or overexertion, it may lead to abdominal pain. If a pregnant woman does not pay attention to the health of her diet or overwork, it may lead to intestinal cramps and other gastrointestinal diseases, causing symptoms of abdominal pain; 3. Pre-eclampsia and ectopic pregnancy can also cause abdominal pain, and pregnant women should check whether there is ectopic pregnancy through maternity checkups; 4. Uterine fibroids can also lead to stomach pain, mostly accompanied by abdominal cramps, abnormal enlargement and other symptoms, and it is recommended to go to the hospital immediately for diagnosis and treatment to avoid delaying the condition.