What is a Placenta Accreta?

Most times, the placenta — which is the organ that your body specifically grows to help nourish your developing baby — attaches to the wall of the uterus for the duration of your pregnancy and detaches within minutes of giving birth. Sometimes, however, certain abnormalities in the placenta can interfere with this process and cause life-threatening issues for new moms.

A placenta accreta is one such example of a misbehaving placenta and happens when the placenta attaches abnormally to the uterine wall. Sometimes the placenta even grows abnormally into the uterine tissue (called placenta increta) or even through it and onto other organs (called placenta percreta), such as onto the bladder. For all intents and purposes, placenta accreta refers to all three of these abnormalities.

Complicating approximately 1 in 533 pregnancies, placenta accreta can lead to life-threatening hemorrhage and potentially even death. This is because the placenta cannot separate from the uterus, so the uterus cannot contract down, which is the main way it stops bleeding after a baby is delivered. This increased blood loss can cost a woman her life if not treated in time. If the placenta has grown into other organs, it can lead to damage to these organs as well.

Thankfully, placenta accreta can often be diagnosed during a woman’s pregnancy well before she delivers. On an ultrasound, the placenta can be seen and certain findings can raise suspicion that an accreta exists. Oftentimes a MRI is done to confirm the diagnosis.

If a woman is found to have a placenta accreta, her pregnancy is now considered to be high risk. She will often be told to avoid vigorous activity, like sexual intercourse, to avoid any bleeding. Delivery is planned weeks before her due date to avoid going into labor and is done via a planned C-section with multiple experienced surgeons. Following the delivery of the baby, the placenta is left in the uterus, and a hysterectomy is done to remove the uterus and placenta together. This is because there is generally no other safe way to remove the placenta in its entirety and avoid excessive bleeding. Only rarely can doctors use alternative treatments (such as medicine to cause the placenta to degenerate) to avoid a hysterectomy, since they usually do not work as well and can have other risky complications.

Sometimes it is not known before delivery that a woman has a placenta accreta; in these cases, it is only diagnosed after she starts to bleed profusely and other causes of bleeding are ruled out. Again, the treatment is almost always a hysterectomy, though in this case, blood loss is often higher since it was not planned ahead of time. Most women in this scenario will require a blood transfusion and often a stay in the intensive care unit after delivery.

The greatest risk factor for developing placenta accreta is having had a C-section before, and in the current pregnancy having the placenta lie over the old scar in the uterus. Having a placenta previa is another major risk factor, as are advanced maternal age (age greater than 35), smoking, and prior uterine surgeries.

Sources:

• Y Oyelese and JC Smulian
• Placenta previa, placenta accreta, and vasa previa
• Obstet Gynecol
• April 2006 – Volume 107 – Issue 4 – pp 927-941.
  The American College of Obstetricians and Gynecologists
• Committee Opinion #52: Placenta accreta.

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