Rationale and Objectives
The role of magnetic resonance imaging (MRI) in the diagnosis of placenta accreta remains uncertain. The purpose of this study was to evaluate the incremental benefit of MRI after ultrasound (US) for a large cohort of gravid patients at risk for a placenta accreta.
Materials and Methods
A retrospective review of outcomes in women with risk factors for a placenta accreta between November 1995 and February 2008 was performed. Inclusion criteria were high-risk women with abnormal placenta implantation on US or operative diagnosis of placenta accreta, with or without a prenatal MRI. Delivery mode, diagnosis, and transfusion requirements were compared.
Results
Ranging in age from 19 to 43 years, with zero to five prior cesarean sections, 139 women met inclusion criteria. The MRI was performed in 28.7% (40/139). US, MRI, and operative diagnoses were highly correlated ( P < .001). Women who underwent both US and MRI were more likely to deliver by cesarean hysterectomy ( P < .001). When the cohort is stratified by outcome diagnosis (normal, previa, accreta), no difference in delivery mode is found; regardless of whether subjects were imaged by US alone or US and MRI. Transfusion requirements were highest in the US and MRI group (mean of 3.9 units vs. 0.9 units in the US only group, P < .001).
Conclusion
This study fails to demonstrate that the incremental use of MRI for placenta accreta changes delivery mode in stratified analysis. Patients who underwent both US and MRI were most likely to have a cesarean hysterectomy delivery, and required more blood products, suggesting that undergoing tests may be indicative of an abnormal and at risk patient population.
Placenta accreta is a spectrum of disease characterized by various depths of abnormal placental implantation into and beyond the endometrial lining of the uterus . In this article, the term placenta accreta is used to refer to placenta accreta, increta, and percreta. The two main risk factors for placenta accreta are a history of prior cesarean (C) section and placenta previa. The incidence of this disease spectrum is increasing, primarily because of the rise in C-section delivery rate. Advanced maternal age and multiparity are also associated risk factors . This condition is associated with significant maternal morbidity and mortality, including massive hemorrhage at the time of placental separation, disseminated intravascular coagulopathy, multiorgan failure, and even maternal death . The current standard of care in treating placenta accreta is surgical management, with delivery via C-section, followed by immediate hysterectomy, without attempted placental separation . This procedure is termed a cesarean hysterectomy (C-hyst). An emergent hysterectomy is associated with increased maternal morbidity related to iatrogenic injuries to bladder, ureter, and bowel .
Prenatal diagnosis is essential for appropriate patient counseling, peripartum planning, and multidisciplinary management . In addition to the risks associated with a major surgery and the health care cost, a hysterectomy has social consequences related to the termination of a woman’s childbearing ability . Prenatal ultrasound (US) imaging is the mainstay in the workup of the placenta accreta diagnosis. However, the sensitivity of this test ranges from 60% to 88% . Magnetic resonance imaging (MRI) has been suggested as a more accurate and sensitive imaging modality in the preoperative assessment of these women . However, the medical literature remains unclear if the added information provided by and cost associated with the MRI changes clinical outcomes.
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Methods
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Results
Study Population
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Table 1
Descriptive Statistics of the Women by Delivery Status
Variable By Delivery Status C-section ( n = 84) C-hysterectomy ( n = 49)P Value Mean Range Mean (SD) Mean (SD) Age at delivery 31.2 19–43 30.2 (5.4) 32.5 (4.9) .02 Overall Parity 2.7 0–11 2.5 (1.6) 2.9 (1.5) .07 Prior C-sections 2 0–5 1.9 (1.1) 2.3 (1.3) .11
C-section, cesarean section.
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Table 2
Comparison of Mode of Delivery to Prenatal Diagnostic Imaging Strategy
Operative Diagnosis Delivery Mode and Prenatal Imaging Strategy Vaginal Delivery Cesarean Section Cesarean Hysterectomy Subtotal † Total US US+MR US US+MR US US+MR US US+MR Normal 2 1 63 11 0 0 65 12 77 Previa 0 0 3 2 2 0 5 2 7 Accreta 2 1 4 1 23 24 29 26 55 Subtotal ∗ 4 2 70 14 25 24 99 40 139 Total ∗ 6 84 49 139
MR, magnetic resonance imaging; US, ultrasound.
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MRI
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Operative Diagnosis
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Delivery
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Vaginal delivery
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C-section delivery
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C-hyst delivery
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Transfusion Requirements
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Statistical Analysis
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Discussion
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