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Placenta accreta is a medical condition in which a pregnant woman’s placenta binds too deeply and firmly with her uterine wall. The placenta is a slab-like organ that sits against the inner wall of the uterus and ferries nutrients and oxygen from a mother to a developing fetus via the umbilical cord. Normally, the placenta begins developing upon conception, binds to the endometrium, or innermost layer, of the uterus, and is finally expelled from the body during childbirth. Women who develop placenta accreta, however, often have difficulty expelling the placenta after the child is born and may need surgery to dislodge the placenta. The condition may cause the patient to suffer severe blood loss, require a hysterectomy, or even die in extreme cases.
The uterus, or womb, is a muscular female reproductive organ with four layers; the peritoneum, perimetrium, myometrium, and endometrium. In a healthy reproductive process, the fertilized egg binds to the endometrium and, from the egg, both the fetus and the placenta develop. When the baby is born, the muscular layer of the uterus, the myometrium, contracts to help eject the baby from the body. After the baby is born, the mother’s body will push out the bloody lining and the placenta, which will still be attached to the baby through the umbilical cord, if it hasn’t been cut already.
For unknown reasons, roughly one in 25,000 pregnant women develop placenta accreta. Because it is difficult to diagnose placenta accreta or see it in an ultrasound, this condition usually goes unnoticed until the delivery. Risk factors include placenta previa and history of Cesarean sections. Placenta previa occurs when the placenta is attached to the lower part of the uterus, instead of the upper portion. This condition may cause severe vaginal bleeding before or during delivery as the cervix, the opening at the bottom of the uterus, expands to allow the baby to be expelled. Placenta previa is usually diagnosed in time to take necessary precautions, including preparing for the increased risk of placenta accreta.
There are three forms of placenta accreta, classified based on the depth of invasion into the uterine wall. If the condition is referred to simply as placenta accreta, it implies the least severe form, in which the placenta is bound too deeply in the endometrium, but has not invaded the myometrium. This is the most common of the three, comprising roughly 75% of all placenta accreta cases. The second most common form, placenta increta, penetrates more deeply into the endometrium, invading the smooth muscle of the uterus. The third, rarest type is placenta percreta, which occurs when the placenta crosses the all layers of the uterus, sometimes binding with another organ and causing grave danger to the patient.
Complications of placenta accreta include severe vaginal bleeding, rupture of the uterus, and premature birth. In the case of placenta percreta, the condition may harm not only the uterus, but other organs, such as the bladder, ureters, and kidneys. A physician will generally recommend a Cesarean section to remove the baby and the placenta from the mother, with minimal damage to the mother or child. Because it is dangerous to deliver a baby prematurely, doctors will help patients to carry the baby as long as possible before scheduling the delivery.
Doctors may also recommend a hysterectomy, the surgical removal of the uterus, to prevent the possibility of severe hemorrhaging. If the uterus is removed, the mother will no longer have the ability to conceive, but the operation will greatly increase her chances of surviving. In some patients, placenta accreta may be mild enough that the doctor can surgically remove the placenta and stem the flow of blood while keeping the uterus intact. Still, a hysterectomy is usually the safer choice, particularly because most cases are found during delivery, when action must be taken quickly.