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Placenta accreta spectrum
Background
Overview
Definition
Placenta accreta spectrum refers to a range of conditions characterized by abnormal adherence of the placenta to the uterine myometrium, with varying depths of invasion. It includes placenta accreta, increta, and percreta, representing progressively deeper invasion into the uterine muscle and surrounding structures.
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Pathophysiology
The pathophysiology involves damage to the endometrial-myometrial interface of the uterine wall, which normally prevents excessive invasion of the placenta. This damage can lead to abnormally deep placental anchoring villi and trophoblast infiltration.
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Epidemiology
The incidence of placenta accreta spectrum varies depending on obstetric history and risk factors. It occurs in approximately 1 in 1,000 deliveries, with rates ranging from 0.04% to 0.9%. The prevalence increases from 0.3% in women with one prior Cesarean delivery to 6.74% in those with five or more Cesarean deliveries. Among women with placenta previa and no prior Cesarean deliveries, it occurs in 3% of cases. In the US, the rate of placenta accreta was estimated to be 1 in 272 among women with a birth-related hospital discharge diagnosis.
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Risk factors
Risk factors of placenta accreta spectrum include prior Cesarean delivery, placenta previa, prior history of placenta accreta spectrum, Cesarean scar pregnancy, uterine artery embolization, intrauterine adhesions (Asherman syndrome), and endometrial ablation.
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Disease course
Antenatal placenta accreta spectrum has no typical clinical presentation, with diagnosis suspected based on risk factors. The clinical course of placenta accreta spectrum can be complicated by severe hemorrhage during and following C-section due to the abnormal placental-uterine separation at the time of delivery, leading to significant maternal morbidity and mortality, including the need for Cesarean hysterectomy Antenatal diagnosis of placenta accreta spectrum relies on imaging, primarily obstetric ultrasound, which identifies features such as vascular lacunae (multiple linear, irregularly shaped placental spaces; approximately 80% sensitivity in the second or third trimester), loss of the hypoechoic zone, and turbulent blood flow on Doppler. While ultrasound demonstrates high sensitivity and specificity, it does not reliably predict the depth of invasion, and the absence of ultrasound findings does not preclude a diagnosis of placenta accreta spectrum. MRI is not routinely preferred, and final confirmation is made by histologic examination after Cesarean hysterectomy.
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Prognosis and risk of recurrence
Maternal morbidity and mortality can occur due to complications, such as life-threatening hemorrhage requiring transfusion hysterectomy. The rate of maternal mortality is estimated at 0.05%.
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Guidelines
Key sources
The following summarized guidelines for the evaluation and management of placenta accreta spectrum are prepared by our editorial team based on guidelines from the Eastern Association for the Surgery of Trauma (EAST 2025), the Royal College of Obstetricians and Gynaecologists (RCOG 2019), and the American College of Obstetricians and Gynecologists (ACOG/SMFM 2018).
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Screening and diagnosis
Classification and risk stratification
Risk factors
As per RCOG 2019 guidelines:
Recognize that the major risk factors for placenta accreta spectrum are history of accreta in a previous pregnancy, previous Cesarean delivery (rising with the number of previous C-sections) and other uterine surgery, including repeated endometrial curettage.
B
Inform patients requesting elective Cesarean delivery for non-medical indications about the risk of placenta accreta spectrum and its consequences for subsequent pregnancies.
E
Diagnostic investigations
Ultrasound: as per RCOG 2019 guidelines, recognize that ultrasound is highly accurate when performed by a skilled operator with experience in diagnosing placenta accreta spectrum.
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MRI
Medical management
Setting of care: as per RCOG 2019 guidelines, ensure care of patients with placenta accreta spectrum is provided by a multidisciplinary team in a specialist center with expertise in diagnosing and managing invasive placentation.
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Expectant management
Therapeutic procedures
Blood product transfusion: as per RCOG 2019 guidelines, discuss additional possible interventions in case of massive hemorrhage, including cell salvage if available.
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Interventional radiology
REBOA
Setting of delivery
Timing of delivery
Perioperative care
Considerations for anesthesia
As per RCOG 2019 guidelines:
Choose anesthetic technique for C-section in patients with placenta accreta spectrum by the anesthetist conducting the procedure in consultation with the patient before surgery.
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Inform patients that the surgical procedure can be performed safely with regional anesthesia, but it may be necessary to convert to general anesthesia if required and ask to consent to this.
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Surgical interventions
Cesarean hysterectomy: as per RCOG 2019 guidelines, prefer performing C-section hysterectomy with the placenta left in situ over attempting to separate it from the uterine wall.
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Uterus-sparing surgery
Ureteric stenting
Specific circumstances
Patients with placenta accreta diagnosed intrapartally
As per RCOG 2019 guidelines:
Delay C-section until the appropriate staff and resources have been assembled and adequate blood products are available if at the time of an elective repeat C-section, where both mother and baby are stable, it is immediately apparent that placenta percreta is present on opening the abdomen. Consider closing the maternal abdomen and urgently transferring to a specialist unit for delivery.
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Leave placenta in situ and perform an emergency hysterectomy if unsuspected placenta accreta spectrum diagnosed after the birth of the baby.
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Patient education
General counseling
As per RCOG 2019 guidelines:
Ensure that any patients giving consent for C-section understands the risks associated with C-section in general, and the specific risks of placenta accreta spectrum in terms of massive obstetric hemorrhage, increased risk of lower urinary tract damage, the need for blood transfusion and the risk of hysterectomy.
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Inform patients that the surgical procedure can be performed safely with regional anesthesia, but it may be necessary to convert to general anesthesia if required and ask to consent to this.
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