The feeling of tightness in the stomach that occurs in the sixth month or so of pregnancy is caused by irregular contractions of the uterus. For the vast majority of pregnant women, this symptom is a physiological phenomenon. With the increase of gestational months after pregnancy, the sensitivity of the uterus to various stimuli will increase accordingly. If standing or walking for a long time, overwork, emotional fluctuations, and stimulation of fetal movement, etc., may induce irregular uterine contractions, and the symptom of tightness and hardness of the abdomen will appear. Uterine contractions are ineffective uterine contractions that do not cause dilatation of the uterine orifice and descent of the fetus, and are rapidly relieved and disappear within a few minutes after bed rest. Most false uterine contractions, which occur at night, are more frequent and obvious.