A woman with a cesarean-scarred uterus has a higher risk of having placenta accreta (the placenta invades the uterine muscle sometimes growing through it into other organs) in a subsequent pregnancy compared with women who have no uterine scar, and that risk rises as she accumulates more scars. A woman with a cesarean scar is also more likely to have placenta previa in combination with accreta than women who have placenta previa and unscarred uteruses. One researcher looking at cesarean-scar ectopic pregnancy theorized that if the embryo tries to grow inside the cesarean scar, you get an ectopic pregnancy. If only the placenta grows inside the scar but the embryo develops inside the uterus, you get placenta accreta.

-- Henci