Most of the time, the placenta performs perfectly. But problems can occur, particularly during the second half of pregnancy.
In some instances, the placenta gets damaged by infections or blood clots. These abnormalities can cause miscarriage, poor fetal growth, prematurity, and excessive maternal bleeding at delivery. If this happens to you, your doctor will examine your placenta after delivery and perhaps send it to a laboratory to help identify the cause of the problem. In some cases, the placenta can peel away from the uterine wall, attach too firmly, or attach in the wrong place. Sometimes vaginal bleeding alerts you to placental problems; other times, they're picked up at a routine ultrasound or exam. But bleeding is usually the hallmark of these problems, so call your doctor at the first sign of blood.