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.

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) was larger in massive hemorrhage group (166 [108-214] cm vs. 70 [43-112] cm 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 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.