define placenta previa
Placenta previa is a pregnancy problem in which the placenta blocks the cervix. The placenta is a round, flat organ that forms on the inside wall of the uterus soon after conception. During pregnancy, it gives the baby food and oxygen from the mother. In a normal pregnancy, the placenta is attached high up in the uterus, away from the cervix. In placenta previa, the placenta forms low in the uterus and covers all or part of the cervix. If placenta previa is present during labor and delivery, it can cause problems for both mother and baby. 1  The mother may lose a lot of blood, which can be dangerous for both her and her baby.