The main complication is heavy bleeding that may occur before or during childbirth. Bulky blood loss is life-threatening to the mother and fetus. Moreover, in case of an emergency cesarean section, the baby may be born very prematurely, without its major organs, such as the lungs, having developed.
Another much feared complication is the likelihood of the placenta praevia becoming a placenta accreta. This happens when the placenta implants deeply in the uterus and does not finish taking off at the time of delivery, which can cause massive bleeding and have to resort to a hysterectomy (removal of the uterus).