Placenta previa is a condition where the placenta partially or fully covers the opening of the cervix, which can lead to dangerous bleeding during pregnancy or childbirth. It typically develops after 24 weeks of pregnancy and is diagnosed via ultrasound. Potential complications include hemorrhage, shock, fetal distress, premature delivery, and even death of the mother or baby. Treatment focuses on limiting activity and avoiding any causes of bleeding, with emergency caesarean delivery often required to deliver the baby safely.