Abnormal placentation: the necessity for preoperative magnetic resonance imaging

Abstract Background:Placenta accreta spectrum (PAS) is characterized by abnormal placental adherence that increases the risk of maternal hemorrhage and death. Current literature suggests lower rates of maternal morbidity and mortality when placenta accreta spectrum is diagnosed or suspected prenatally. We examined the use of preoperative imaging in predicting PAS with the goal of assessing concordance between imaging modalities and impact of differential imaging on morbidity. Methods: Women with suspected placenta accreta spectrum who delivered at our institution from 2010-2018 were included. Perioperative diagnoses, imaging, and pathology reports were abstracted from medical records. Descriptive statistics, ANOVA, chi square, multinomial logistic regression, Cohen’s kappa analyses were performed. Results: There were 152 cases with suspected placenta accreta spectrum from 2010-2018 with 131 (86.2%) cases confirmed by final pathology. Of the confirmed cases, there were 38 (25%) accretas, 62 (40.8%) incretas, and 31 (20.4%) percretas. Magnetic resonance imaging (MRI) more accurately diagnosed placenta accreta spectrum (39% of cases) than ultrasound (25%). Cohen’s kappa for ultrasound versus pathology was 0.02836, demonstrating slight inter-rater agreement (p=0.55) than 0.5087 in the MRI versus pathology group (p=0.08). Of the 107 patients requiring resuscitative blood products, indicators of morbidity, the percreta group had significantly greater mean estimated blood loss (4.8L) with longer mean length of hospital stay (p=0.014) compared to increta (3.1L) and accreta (2.6L) (p=0.04). Conclusions: This study supports the role of pelvic magnetic resonance imaging for antepartum diagnosis of placenta accreta spectrum. Accurate diagnosis is essential for the perioperative coordination of care to improve maternal outcomes and reduce mortality.