The stomach is hard and tight and the fetus may be performing various activities in the uterine cavity of the pregnant mother. A hard and tight stomach is caused by uterine contractions, which can be physiologic or pathologic. Physiologic uterine contraction: If the uterine contraction lasts for a relatively short period of time and disappears quickly, it is physiologic. This is because false contractions will often occur in the late stages of pregnancy and in preparation for labor later. The fetus may be moving at this time, so there is no need to be overly nervous. Pathological uterine contractions: it is important to note that if you have not yet reached the full-term range of pregnancy, the pain caused by uterine contractions is more pronounced, lasts for a longer period of time, becomes more and more regular, and may also cause preterm labor. If the tightness of the stomach during pregnancy continues unrelieved, you need to go to the hospital in time, do the relevant examination, and take treatment measures according to the situation.