The weakening of fetal movement at 5 months may be caused by intrauterine oxygen deprivation, sleep, etc. Fetal movement should be monitored regularly, and any abnormality should be examined in the hospital promptly. 1. Sleep: usually pregnant women can feel fetal movement at 20 weeks of pregnancy (i.e. 5 months), and fetal movement is more active at night and in the afternoon, fetal movement will be weakened or disappear when the fetus sleeps, which is a normal phenomenon. 2. Intrauterine hypoxia: for example, umbilical cord entanglement, placental abnormalities, congenital cardiovascular disease can lead to intrauterine hypoxia, fetal movement is weakened. In this case, you should record the normal range of the number of fetal movements at regular intervals according to the requirements, and compare it with the normal range. If the value decreases by more than 50%, you need to be vigilant, and it is recommended to go to the hospital in time to find out the cause.