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Placenta accreta can be a serious and potentially life-threatening condition. The specialists at Brigham and Women’s Hospital compiled the following guidelines for the obstetric care of accreta patients. These guidelines reflect current research and the combined experience and knowledge of our group.
The placenta is abnormally adherent to the uterus and extra effort is required to remove it. The attachment site often bleeds heavily when the placenta is removed.
A pathologist identifies trophoblast in direct contact with the myometrium. This often, but not always requires a hysterectomy specimen for confirmation.
A pathologic diagnosis in which the placental trophoblast invades into the myometrium.
The placenta penetrates the entire uterus, to or through the serosa. The placenta may directly contact or invade surrounding structures (such as the urinary tract). This may be identified clinically or pathologically.
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: 1st (primary)
Previous Cesarean Deliveries: 2nd
Previous Cesarean Deliveries: 3rd
Previous Cesarean Deliveries: 4th
Previous Cesarean Deliveries: 5th
Previous Cesarean Deliveries: 6th or more
“Placenta Accreta,” American Journal of Obstetrics and Gynecology, Volume 203, Issue 5, 430 - 439
Other risk factors include:
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:
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.
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:
See also information on placenta accreta written specifically for the patient.
Interventional Radiology (IR)
Established in 2008, our team has cared for hundreds of women with uterine and placental disorders, including placenta accreta.
In addition to delivery planning and management, we accept transfers of complicated postpartum patients and provide inter-pregnancy care, including management of retained accretas.
Please consider donating to the BWH Program for Surgical Obstetrics and its Placental Abnormalities Initiative. Funds will be used to support our research programs, build communication and education tools, and make sure that our Labor and Delivery unit is equipped with state-of-the art technology to assist women who hemorrhage in childbirth. Please indicate at the time of donation that you would like to direct the funds to the Surgical Obstetric/Placenta Accreta Program.
Access research and information about placenta accreta and delivery.
Offer pertinent information and support to accreta patients. Common accreta myths explained and dispelled.
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This information was made possible with a donation from the Hess Foundation.