Placenta previa means placenta lies lower in the region of uterus. Placenta is connection between mother and baby and has a connecting cord called umbilical cord. Whenever placenta lies lower in the uterus there is usually separation of this placenta before delivery as the uterus enlarges and fetus grows. Hence you should avoid having intercourse , avoid lifting heavy weights, avoid straining at stools. You will need to undergo another ultrasound after completing 8 months. Usually placenta which lies lower in the uterus goes on top but so,e cases can still lie lower in the uterus.