Heavy bleeding during the last stages of your pregnancy can cause complications with childbirth. The two most common conditions that cause heavy bleeding are placenta previa, and placental abruption.
Placenta previa occurs when the placenta either partially or completely blocks the opening in the cervix. It can be a serious problem if you go into labor with placenta previa. If a normal vaginal delivery is tried, the part of the placenta covering the cervix can separate from the uterine wall when the cervix dilates. This can cause serious bleeding, and it may be fatal for the mother and/or the baby. Because of this, cesarean delivery is recommended for placenta previa.
Heavy bleeding can also be caused from placental abruption, which happens when the placenta separates from the wall of the uterus during the pregnancy. This can reduce the supply of blood and oxygen to the baby. If the abruption is serious, the blood vessels from both the mother and baby can rupture, and they can suffer serious blood loss. Usually if the abruption is significant, a cesarean delivery is recommended.