It is not normal for a baby in the seventh month of pregnancy to suddenly not move for the whole night. Most of the sudden decrease in fetal movement of the baby in the seventh month of pregnancy is caused by considering the weakened function of the placenta, the poor quality of amniotic fluid, and abnormalities in the umbilical cord. Weakened placental function refers to the decline and aging of the placenta, which will affect the baby’s oxygen supply, resulting in a decrease in fetal movement. Poor quality of amniotic fluid, such as cloudy and polluted amniotic fluid, will affect the baby’s respiration and metabolism, and will also cause fetal hypoxia and decreased fetal movement. The umbilical cord is abnormal, umbilical cord torsion, umbilical cord around the neck may cause the umbilical cord blood supply is not good to cause hypoxia fetal movement reduction. Seven-month-old babies suddenly do not move at night, must go to check the cause, such as fetal heart monitoring and ultrasound, if there is an abnormality can be timely intervention, to avoid delays in the condition.