Mid-pregnancy contractions are caused by sudden and strenuous exercise of pregnant women, keeping the same position for a long time or recent overwork. 1. Sudden and strenuous exercise: If a pregnant woman does sudden and strenuous exercise such as running, cycling or coitus, it may cause contractions due to external stimulation of the uterus, avoiding strenuous exercise can prevent contractions in mid-pregnancy. 2. Keeping the same position for a long time: If a pregnant woman keeps the same position for a long time, such as lying on her side or standing for too long, and does not pay attention to proper exercise and change position, contractions may occur, pay attention to change the position when resting, can prevent the appearance of irregular contractions. 3. Overwork: The fetus grows faster in mid-pregnancy and the burden on the pregnant woman is heavier. If a pregnant woman does not pay attention to rest for a period of time, overwork may also lead to contractions, pregnant women can ensure adequate sleep, avoid overwork, to prevent contractions. Contractions in mid-pregnancy may also have other causes, it is recommended that contractions do not ease the timely visit to the hospital, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.