Comparison of MRI findings for predicting massive hemorrhage during cesarean section in patients with placental malposition: partial placental volume of lower uterine segment is an accurate and objective indicator.

Abstract

Purpose: To comprehensively compare the diagnostic ability and inter-reader agreement of magnetic resonance imaging (MRI) findings for predicting massive hemorrhage after cesarean section in patients with placental malposition, aiming to identify the most reliable and objective indicators.

Methods: Totally, 148 consecutive patients with placental malposition underwent MRI and cesarean section at our hospital between January 2014 and July 2021. The patients were divided into massive and non-massive hemorrhage groups. MRI findings of placenta accreta, placental position, and placental volume were evaluated by two radiologists, and inter-reader agreement was calculated. Diagnostic ability for predicting massive hemorrhage was evaluated using receiver operating characteristic analysis.

Results: Intraplacental T2 dark bands (100% vs. 58.2%, p = 0.001), placental bulge (50% vs. 3.7%, p < 0.001), loss of retroplacental T2 hypointense line (100% vs. 67.2%, p = 0.01), myometrial thinning (92.9% vs. 57.5%, p = 0.009), total placenta previa (64.3% vs. 23.9%, p = 0.033), and anterior placenta (35.7% vs. 10.5%, p = 0.02) were significantly observed in massive hemorrhage group. Partial placental volume of lower uterine segment (PV_partial) was larger in massive hemorrhage group (166 [108-214] cm³ vs. 70 [43-112] cm³ p < 0.001), had the second highest intraclass correlation coefficient (0.84), and had the highest area under the curve (0.81) for diagnosing massive hemorrhage.

Conclusion: This study revealed PV_partial is an accurate and objective indicator for massive hemorrhage, independent of radiologists' experience. This indicator potentially enables prediction of massive hemorrhage, improving pre-operative planning in high-risk pregnancies.