Caring for the Placenta Accreta Patient

According to the Society of Maternal-Fetal Medicine, the frequency of placenta accreta has increased from 0.8 per 1,000 deliveries in the 1980s to 3 per 1,000 deliveries in the past decade. The cause of this increase is multifactorial, and may be attributed to higher cesarean delivery rates, rising maternal age, and increased use of infertility treatments.

The primary risks for placenta accreta are prior cesarean deliveries and the presence of placenta previa. Below is the frequency of accreta based on these two factors.

Previous Cesarean Deliveries: 1^st (primary)

• Presence of Placenta Previa: 3.3
• Absence of Placenta Previa: 0.03

Previous Cesarean Deliveries: 2nd

• Presence of Placenta Previa: 11
• Absence of Placenta Previa: .2

Previous Cesarean Deliveries: 3rd

• Presence of Placenta Previa: 40
• Absence of Placenta Previa: .1

Previous Cesarean Deliveries: 4th

• Presence of Placenta Previa: 61
• Absence of Placenta Previa: .8

Previous Cesarean Deliveries: 5th

• Presence of Placenta Previa: 67
• Absence of Placenta Previa: .8

Previous Cesarean Deliveries: 6th or more

• Presence of Placenta Previa: 67
• Absence of Placenta Previa: 4.7

“Placenta Accreta,” American Journal of Obstetrics and Gynecology, Volume 203, Issue 5, 430 - 439

Other risk factors include:

• Maternal age over 35
• Prior uterine surgery or curettage
• In vitro fertilization (IVF)
• Asherman syndrome

High mortality rates (over 1 percent) have been described with accreta, but this information should be interpreted with caution³. Quoted numbers originally referred to placenta percreta, and were generated from a survey. Patients and providers should understand that this is one of the most dangerous conditions in obstetrics, but precise mortality rates have yet to be reported.

The term “accreta” calls to mind a dangerous condition, often with massive hemorrhaging at the time of delivery. Accreta can have a wide range of presentations, and the diagnosis should be considered in a variety of scenarios. In addition to the patient with a previa and prior cesarean sections, below are additional examples of the hundreds of accreta patients we have managed at BWH:

• A patient with a history of myomectomy, now with the placenta focally adherent to the surgical site
• An IVF patient who delivers her baby vaginally, but her placenta wouldn’t deliver with manual extraction attempts
• A patient with two prior cesarean sections and a resolved placenta previa
• A woman who had an unremarkable delivery, but her placental pathology returned with evidence of placenta accreta

Understanding these patients’ risk factors and clinical presentations is essential for patient counseling and a safe delivery.

All patients with risk factors should be evaluated carefully for accreta during pregnancy. An antepartum diagnosis is important because it allows for multidisciplinary delivery planning and detailed patient counseling. However, diagnosis can sometimes be difficult, especially in the absence of placenta previa, so clinical suspicion is always warranted for at-risk patients.

Ultrasonography: Diagnosis is typically made based on ultrasound findings in the second and third trimesters. Indicators include multiple vascular lacunae within placenta, blood vessels bridging uterine-placental margin, retroplacental myometrial thickness of less than 1 mm and a loss of the normal hypoechoic retroplacental zone. We recommend using sonologists experienced with this diagnosis, and alerting them that the patient has risk factors for accreta.

MRI: MRI is not essential in accreta care, but may be helpful in select circumstances. These include limited ultrasound views, and concern for percreta with organ invasion. We consider obtaining an MRI if it will clearly change patient management. The American College of Radiology recommends that intravenous gadolinium be avoided during pregnancy, but MRI is otherwise considered safe.

Intrapartum Diagnosis: Sometimes an accreta diagnosis can’t be made or confirmed prior to delivery, especially in more atypical situations. Providers should have a high index of suspicion when an adherent placenta, or highly vascular uterus is encountered, especially in patients with risk factors. Alerting staff, preparing for hemorrhage, and possibly calling for surgical help can be life saving for some of these patients.

• Consider consulting a specialized center, such as Brigham and Women’s Hospital.
• Offer individualized and multidisciplinary care for every potential accreta patient.
• An experienced team that includes an obstetric surgeon and other specialists, depending on the patient’s specific condition, should perform the delivery.
• A scheduled delivery is preferable, but be sure to also make a plan for a possible emergency delivery.
• Antepartum care, including hospital admission plans, should be directed by individual circumstances and other conditions, such as placenta previa, maternal age, or uterine fibroids.

Accreta patients face a uniquely high-risk delivery and potentially difficult recovery, so be sure to offer a greater degree of counseling. The patient will benefit from education about accreta, the options available to her for delivery and how she can best recover both physically and mentally. (See resources below.)

When you meet with accreta patients, be sure to discuss:

• The potential for hemorrhage and transfusion
• The possibility of a hysterectomy
• Potential for premature delivery
• Circumstances that may lead to decreased activity or hospital admission
• The increased risk for anxiety, post-partum depression and post-traumatic stress disorder after delivery; these conditions’ warning signs and resources for help
• Sources of social support

See also information on placenta accreta written specifically for the patient.

Delivery timing

• Placenta accreta with previa is generally delivered in the late-preterm period.
• Delivery as early as 34 weeks is appropriate and has been recommended. However, safe delivery at later gestational may be safe, and is practiced at a number of accreta centers.
• Exact timing should depend on the patient’s individual circumstances, including pregnancy complications, risk factors for preterm labor, and the hospital’s ability to perform a safe, unscheduled delivery.
• Patients without a placenta previa or history of extensive uterine surgery may be candidates for a term delivery (after 37 weeks).

Surgical Team

• In addition to an experienced obstetrician, accreta patients are usually managed by a high-risk OB anesthesia team.
• Involvement of an urologist for ureteral stenting, bladder resection or repair is helpful in select cases.
• Additional pelvic surgeons may be included, as needed.

Interventional Radiology (IR)

• Use of intra-arterial balloon catheters and intraoperative or postoperative embolization has been described. The only available randomized trial showed that balloon use made no meaningful difference for patients with previa and suspected accreta.
• Catheter placement and embolization have their own risks, and these should be weighed against expected benefits, on a case-by-case basis.
• Embolization can be very helpful to treat postpartum hemorrhage, and 24-hour availability of these services can improve accreta care.
• A hybrid OR allows surgical and interventional radiology procedures to integrate seamlessly. Many accreta centers have such facilities available in their hospitals.

Anesthesia

• Patients with accreta may be managed with neuraxial anesthesia (epidural with or without a spinal anesthetic), general anesthesia, or a combination of both. Centers differ on their approach to general anesthesia, and this is important to discuss in the delivery planning stages.
• Consultation with the high-risk obstetric anesthesiology team is essential. They will manage transfusion planning and implementation, venous access, invasive monitoring, required vasopressor support, and safe transport to interventional radiology or the intensive care unit when appropriate.

Hemorrhage Management

• Delivery should be planned on a unit with 24-hour access to full blood bank services and a massive transfusion protocol.
• Many patients at risk for a large hemorrhage receive autologous blood, collected with a cell salvage system. This may be particularly important if limited blood is available for an individual patient, but may be safely considered upon patient request.
• Relatively new drugs, such as fibrinogen concentrate and tranexamic acid, are currently being tested and used for obstetric hemorrhage.

Uterine Conservation

• Cesarean section with hysterectomy has been the standard of care for most patients with a significant accreta. All patients with suspected accreta should be prepared for this possibility.
• Patients with a more focal accreta (only one portion is adherent), especially in the absence of a previa, may come through their delivery without a hysterectomy.
• Uterine conserving measures have been described over the last decade, even with more severe previa/accretas. This usually involves leaving part or the entire placenta attached, and requires careful follow-up.
• Uterine conservation carries its own set of risks. Patients considering this need to be counseled at an experienced Center of Excellence, with careful informed consent.

Methotrexate

• Patients who have undergone conservative management, or who have a focal accreta diagnosed postpartum, are sometimes treated with methotrexate. This is based on experience using the medication for early abnormal (ectopic) pregnancies.
• Methotrexate acts on dividing cells. Given that the placental cells cease proliferation prior to delivery, this drug would not be expected to work in the postpartum period.
• There are no controlled studies or trials showing that methotrexate is effective in this scenario.
• Patients with a rising HCG level postpartum should be evaluated for unrelated trophoblastic disease.

• After a complicated delivery, accreta patients are at risk for persistent coagulopathy and anemia, thromboembolism, and renal, cardiac and other organ dysfunction. Patients require close monitoring, sometimes in an intensive care setting.
• Patients may experience anxiety or even post-traumatic stress disorder after delivery. Support and professional services should be offered as needed.
• Patients who have experienced a focal accreta or incidentally-found pathologic accreta are at risk for retained, adherent placental tissue. These patients should be managed by experienced obstetrician/gynecologists.
• Patients who preserve their uterus in the face of accreta should be counseled carefully prior to experiencing another pregnancy. Recurrence rates of 25-35 percent have been described.