How many days the placenta 3 can last is not a direct judgment, the placenta 3 is the clinical ultrasound examination of the placenta after the results, and can not be based on the results of the examination to determine when to give birth. Under normal circumstances, placental level 3 indicates that the placenta has matured and tends to age, which may have a certain impact on fetal growth and development, and if it lasts for a longer period of time, it may lead to hypoxia, asphyxia and death. Clinically, after the emergence of placenta 3, it is necessary to count the fetal movement every day, and at the same time, it is also necessary to regularly consult a doctor for fetal heart monitoring examination. If you find that there is fetal hypoxia and other conditions, you need to consult a doctor in time to inhale oxygen, and if necessary, you need to give birth in time, so as not to affect the development of the fetus.