Placenta hypoplasia generally need to lie down for how long mainly depends on whether there is vaginal bleeding and whether there is upward mobility with the pregnancy, generally need to lie down until there is no vaginal bleeding and the position of the placenta is normal, there is no specific time. 1. Vaginal bleeding: placenta previa may lead to painless vaginal bleeding, the amount of bleeding is generally related to the location of the placenta, at this time you need to lie down and rest, generally need to lie down until there is no longer recurrent vaginal bleeding; however, if the placenta is only previa and there is no bleeding, you do not need to lie down and only need to prohibit strenuous exercise and sexual life. 2. Whether the placenta position has moved up with the pregnancy: if there is a small amount of vaginal bleeding, but the placenta position has gradually moved up with the pregnancy and has reached the normal position, generally do not need to continue to lie down, but still need to pay attention to do not exercise strenuously. If the placenta is low, there is usually no need to worry too much, and regular checkups are sufficient. During pregnancy, pay attention to more rest, at the same time should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, by the doctor to clarify the diagnosis, and cooperate with the doctor to deal with the symptoms.