The most common placenta problems are placenta previa, placenta accreta, and placenta abruptio. These conditions range is severity from mild to life-threatening for both mother and baby, although death of the mother is rare. The placenta is a life-support system for the developing baby, and attaches to both the inside of the uterus and the umbilical cord. It also filters waste from the baby's blood and adds it to the mother's blood for elimination. Any woman experiencing symptoms of placenta problems should report them to a health care provider as soon as possible.
If the cervix is completely or partially covered by the placenta, it is called placenta previa, and occurs in about one out of every 200 pregnancies. Most cases are diagnosed during routine ultrasounds or when a pregnant women reports vaginal bleeding. If placenta previa has not been previously diagnosed and the cervix begins to dilate, heavy bleeding may occur. Risk factors for placenta previa include smoking, advanced maternal age, and previous uterine surgery. A cesarean section must be performed before the onset of labor if the placenta does not move upwards on its own, which happens in about 90 percent of cases.
A placenta deeply embedded in the uterine wall is called placenta accreta, and if it is burrowed through the wall to the bladder it is called placenta percreta. The most common cause of placenta accreta is the placenta implanting into a scar caused by previous cesarean section. These placenta problems occur in about one in 530 births, a number which is increasing due to rising cesarean rates.
Sometimes placenta accreta is discovered before birth during ultrasound. The main symptom, if any, is bleeding later in pregnancy. If it is not diagnosed before birth, the placenta may not detach after delivery, causing severe bleeding. An emergency hysterectomy is needed to stop the bleeding. When accreta is discovered before delivery, a cesarean delivery followed by a hysterectomy will be performed once the fetus is viable.
A placenta partially or completely detached from the uterine wall before the time of birth is called placenta abruptio. This condition occurs in about one in 150 pregnancies. The severe form occurs in about one in 800 to 1,600. Risk factors include smoking during pregnancy, high blood pressure, advanced maternal age, uterine fibroids, and the use of cocaine. It may also be caused by a blow to the abdomen, although this is uncommon.
Symptoms of placenta abruptio include back and abdominal pain, contractions with no relaxation, and vaginal bleeding. If the middle of the placenta becomes detached but the sides remain attached, the blood may become trapped. Women may go into shock without being aware that they are bleeding. If the baby is not mature or the separation is mild, the mother may be carefully observed in the hospital until spontaneous delivery. If the baby is mature enough to survive, an emergency cesarean may be performed.