What Is Placenta Accreta Causes Risks Treatment?

Placenta accreta is a serious pregnancy complication in which the placenta attaches too deeply into the wall of the uterus and does not separate normally after delivery. It is part of a group of conditions called placenta accreta spectrum (PAS) disorders, which range from mild to severe depending on how far the placental tissue invades. The main cause is a placenta implanting over a prior cesarean scar or other uterine surgery site. It can cause severe bleeding around the time of birth, and treatment usually involves a carefully planned cesarean delivery, often with hysterectomy.

What Is Placenta Accreta and How Does It Differ From a Normal Placenta?

In a normal pregnancy, the placenta attaches to the lining of the uterus and peels away cleanly after the baby is born. The uterus then contracts to close off the blood vessels where the placenta was attached, which limits bleeding.

In placenta accreta, the placenta grows into the uterine muscle instead of staying on the surface. The anchoring villi — the tiny finger-like structures that normally grip the uterine lining — go deeper than they should. Because the placenta is stuck, it cannot detach on its own. When it is pulled away or when the uterus tries to deliver it, the blood vessels underneath stay open, and heavy bleeding can follow.

Clinicians group these cases into a spectrum. The terms generally used are:

• Accreta: the placenta attaches directly to the uterine muscle without a normal decidual layer.
• Increta: the placenta grows into the muscle of the uterus.
• Percreta: the placenta grows through the uterine wall and can reach nearby organs such as the bladder.

The deeper the invasion, the higher the risk of serious bleeding and surgical complications. Not every case fits neatly into one category, and imaging does not always predict the depth accurately before delivery.

What Causes Placenta Accreta?

The single most important factor is a previous cesarean delivery combined with a placenta that implants over that scar. When the uterine wall has been cut, the scar tissue that forms lacks the normal decidual lining. A placenta that lands on that area can grow into the muscle because there is no healthy layer to stop it.

This is why the risk climbs with each prior cesarean. A person with one prior cesarean and a placenta previa (placenta covering the cervix) has a meaningfully higher risk than someone with no uterine surgery. With more prior cesareans, the risk rises further. The combination of placenta previa and multiple prior cesarean deliveries is the setting in which placenta accreta spectrum is most often seen.

Other factors linked to the condition include:

• Prior uterine surgery, including myomectomy (fibroid removal) or uterine scraping procedures
• Placenta previa, with or without prior surgery
• Being older at the time of pregnancy
• Having had multiple pregnancies
• Prior history of placenta accreta
• Assisted reproduction, which some studies associate with higher risk

The exact biology is not fully understood. The condition appears to involve abnormal interaction between the placental tissue and the uterine lining rather than a single clear cause. Having one risk factor does not guarantee the condition, and some cases occur without any known risk factor.

How Common Is Placenta Accreta?

Placenta accreta spectrum is uncommon, but it has become more frequent over recent decades. The rise tracks closely with rising cesarean delivery rates worldwide.

Reported rates vary widely between hospitals and studies, so a single number is hard to state with confidence. What is clear is the trend: as more people have uterine surgery, more cases appear. In centers that handle high-risk pregnancies, PAS is now a regular part of obstetric practice rather than a rare event.

Because the condition is uncommon in any single practice, it is usually managed at specialized centers with teams that include maternal-fetal medicine specialists, experienced surgeons, anesthesiologists, and often urologists or other surgeons when the bladder or other organs may be involved.

What Are the Symptoms and How Is It Diagnosed?

Placenta accreta usually causes no symptoms during pregnancy. Most cases are found on imaging or suspected because of risk factors, not because the pregnant person feels anything unusual. Painless vaginal bleeding in the second or third trimester can occur, often related to placenta previa, but bleeding alone does not confirm accreta.

Diagnosis relies mainly on ultrasound, performed by someone experienced in evaluating the placenta. Findings that raise concern include:

• Loss of the normal clear zone between the placenta and the uterine wall
• Abnormal blood vessels crossing the placenta–uterine boundary
• Thinning of the uterine muscle over the placenta
• Placental tissue bulging into or through the uterine wall

Magnetic resonance imaging (MRI) is sometimes used to clarify the depth of invasion or involvement of nearby organs, though it is not always necessary. Neither ultrasound nor MRI is perfect. In some cases the diagnosis is only confirmed at the time of delivery, when the placenta fails to separate.

Because the condition can be missed before birth, anyone with placenta previa and prior uterine surgery is generally watched closely, even if early imaging looks reassuring.

What Are the Risks of Placenta Accreta?

The main danger is severe hemorrhage around the time of delivery. Because the placenta cannot detach normally, attempts to remove it can trigger rapid, heavy bleeding that is difficult to control.

Serious complications can include:

• Life-threatening blood loss requiring transfusion
• Emergency hysterectomy (removal of the uterus)
• Injury to the bladder, ureters, or bowel if the placenta invades through the uterus
• Blood clotting problems triggered by massive bleeding
• Intensive care admission
• Rarely, death

Risks to the baby are mostly tied to preterm delivery. Because planned delivery often happens before the due date to reduce the chance of emergency bleeding, babies may be born early. Preterm birth carries its own set of concerns, including breathing and feeding difficulties.

Placenta accreta also affects future fertility. If hysterectomy is needed, pregnancy is no longer possible. Even when the uterus is preserved, future pregnancies carry a higher risk of the condition recurring.

How Is Placenta Accreta Treated?

Treatment is planned in advance whenever the condition is suspected. The goal is to deliver the baby safely while controlling bleeding and avoiding an emergency.

The standard approach is a scheduled cesarean delivery, usually before the due date, at a hospital with the resources to manage major hemorrhage. The timing is decided by the care team based on the individual situation and how the pregnancy is progressing. Delivery too early risks newborn complications; waiting too long risks emergency bleeding.

There are two broad surgical strategies:

• Cesarean hysterectomy: the baby is delivered and the uterus is removed with the placenta left in place. This avoids trying to peel the placenta away, which is what triggers heavy bleeding. It is the most common approach for confirmed accreta.
• Uterus-preserving surgery: in selected cases, surgeons remove the placenta and repair the uterus, sometimes using techniques to control blood flow. This can preserve fertility, but it carries a higher risk of bleeding and complications, and it is not appropriate for everyone.

Some clinicians use additional measures such as balloon catheters placed in the pelvic blood vessels to reduce blood flow during surgery. Whether these consistently improve outcomes is debated, and practice varies between centers. The evidence is mixed, and no single approach is clearly best for every case.

Blood products are usually prepared in advance, and the surgical team plans for the possibility of significant transfusion. A multidisciplinary team is standard at specialized centers because outcomes tend to be better when the condition is anticipated rather than discovered during an emergency.

Can Placenta Accreta Be Prevented?

There is no way to prevent placenta accreta directly. The most meaningful step is reducing unnecessary uterine surgery. Because prior cesarean delivery is the leading risk factor, avoiding cesareans that are not medically needed lowers the chance of the condition in future pregnancies.

This is not a judgment about any individual birth. Sometimes cesarean delivery is necessary and lifesaving. The point is that each uterine scar adds risk for later pregnancies, so the decision carries weight beyond the delivery itself.

For people who already have risk factors, early and accurate imaging, referral to a specialized center, and careful planning are the main ways to reduce the chance of the most serious outcomes. These steps do not prevent the condition, but they can make it far safer to manage.