Pregnant women in the fourth month of pregnancy suddenly have pain in the right side of the stomach today, which may be physiological factors, such as the enlarged uterus pressing on the abdominal organs; or pathological factors, such as pre-eclampsia, inflammation of abdominal organs, etc., which need to be treated after diagnosis according to the pregnant women’s signs and relevant examinations. I. Physiological pain: Pregnancy: When pregnant women are four months pregnant, the uterus begins to gradually become larger, which pulls and tenses the right uterine ligament and can cause pulling pain, and also has a certain squeezing effect on the annexes and intestinal tubes on the right side of the uterus, which may lead to right side stomach pain. Physiological pain is generally tolerable, can be relieved with the change of position, not accompanied by other abnormal symptoms, such as fever, nausea, etc., generally do not need special treatment. Pathological pain 1, miscarriage: If the pregnant woman has persistent pain aggravated, accompanied by vaginal bleeding, should be alert to the possibility of miscarriage, it is recommended to go to the hospital to do ultrasound to check whether there is a possibility of miscarriage. If it is a pre-eclampsia miscarriage, the pregnant woman needs fetal preservation treatment. 2. Gynecological inflammation: If it is adnexitis, tubal inflammation, etc. on the right side, or inflammation of abdominal organs, such as appendicitis, enteritis, intestinal spasm, intestinal obstruction, etc., it can cause sudden pain in the right side of the abdomen of pregnant women. This kind of pain is usually heavy and cannot be relieved by changing the position, so you need to go to the hospital in time to find out the cause and perform targeted treatment; 3. Acute abdominal disease: if it is appendicitis, pelvic inflammatory disease, acute intestinal obstruction, etc., there will be pain in the right side of the stomach, which is not related to pregnancy, but is caused by abdominal diseases.