MRI of placenta accreta: diagnostic accuracy and impact of interventional radiology on foetal-maternal delivery outcomes in high-risk women.

To assess accuracy and reproducibility of MRI diagnosis of invasive placentation (IP) in high-risk patients and to evaluate reliability of MRI features. Secondary aim was to evaluate impact of interventional radiology (IR) on delivery outcomes in patients with IP at MRI. 26 patients (mean age 36.24 y/o,SD 6.16) with clinical risk-factors and echographic suspicion of IP underwent 1.5 T-MRI. Two readers reviewed images. Gold-standard was histology in hysterectomised patients and obstetric evaluation at delivery for patients with preserved uterus. Accuracy and reproducibility of MRI findings were calculated. Incidence of IP was 50% (13/26) and of PP was 11.54% (3/26). MRI showed 100% sensitivity (95% CI = 75.3-100%) and 92.3% specificity (95% CI = 64.0-100%) in the diagnosis of IP. Gold-standard was histology in 10 cases and obstetric evaluation in 16. MRI findings with higher sensitivity were placental heterogeneity, uterine bulging and black intraplacental bands. Uterine scarring, placental heterogeneity, myometrial interruption and tenting of the bladder showed better specificity. MRI inter-rater agreement with Cohen's K was 1. 11 patients among 14 with MRI diagnosis of IP received IR assistance with positive impact on delivery outcomes in terms of blood loss, red cells count, intense care unit length of stay, days of hospitalisation and risk of being transfused. MRI is an accurate and reproducible technique in prenatal diagnosis of IP. MRI helps planning a safe and appropriate delivery eventually assisted by IR, which positively affects foetal and maternal outcomes. The adoption of MRI evaluation in patients with high risk of invasive placentation allows a more accurate diagnosis in terms of both presence of the disease and its extension to or through or even beyond the myometrium. This led to a better dedicated delivery management with eventual adoption of interventional radiology with a global positive effect on foetal and maternal outcomes.