The hardness and tightness of the stomach every afternoon in the fourth month of pregnancy may be caused by occasional contractions, uterine enlargement, pre-miscarriage, gastrointestinal discomfort and other reasons. 1. Occasional contractions: four months pregnant stomach every afternoon hard and tight, short duration, long interval, rest can be relieved, not accompanied by other uncomfortable symptoms, is considered to be the occasional afternoon false uterine contractions, without special treatment. 2. Uterine enlargement: with the gradual development of the fetus in the fourth month of pregnancy, the uterus will gradually increase in size, and the belly may be stretched out and taut, so that the stomach will be hard and taut every afternoon. 3. Pre-eclampsia: four months pregnant stomach every afternoon hard and taut, contractions will gradually become stronger, the frequency gradually increased, measuring the length of the cervical canal becomes shorter, may be caused by pre-eclampsia, to go to the hospital through the birth control gradually relieve contractions. 4. gastrointestinal discomfort: four months pregnant with more serious constipation, indigestion and other gastrointestinal discomforts, defecation difficulties will lead to the gas can not be discharged, the pressure in the intestinal lumen increases, the phenomenon of the stomach hard and taut. Indigestion leads to abdominal distension, which can also cause the stomach to become hard and tight every day. Four months pregnant stomach hard and tight every afternoon, accompanied by abdominal pain, vaginal bleeding and other symptoms should be considered abnormal, timely medical attention.