Lower abdominal pain in early pregnancy can be classified according to its etiology: physiological pain and pathological pain. The main cause of physiologic pain is the gradual enlargement of the uterus as the pregnancy progresses and the embryo develops. The enlarged uterus will produce adaptive changes, with excessive stretching of the ligaments around the uterus and compression of the surrounding tissues and organs by the enlarged uterus. As a result, some pregnant women may feel a vague pain in the lower abdomen. However, this pain is short-lived and mild, usually called round ligament pulling pain, which is a normal physiological phenomenon and can be treated without special treatment. Pathological pain refers to pain in the lower abdomen caused by illnesses during pregnancy, which can include preterm abortion, ruptured corpus luteum, and torsion of ovarian cysts. This pathological pain is usually more severe and lasts longer. Once pathological pain occurs during pregnancy, the patient needs to be seen immediately at a local hospital to identify the cause of the abdominal pain. Then, depending on the cause of the pain, symptomatic supportive treatment should be given. In summary, there are many causes of stomach pain in the fourth trimester of pregnancy, and pregnant women need to pay attention to distinguish whether the pain is physiological or pathological to avoid delaying the condition.