Risk Stratification Based on Imaging Findings for Pregnancies With Subamniotic or Subchorionic Hematoma on Placental MRI

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BACKGROUND: Subamniotic or subchorionic hematoma (SAH/SCH) is associated with diverse pregnancy outcomes. The clinical implications of accompanying oligohydramnios and hemorrhagic amniotic fluid on MRI remain unclear. PURPOSE: To investigate the importance of oligohydramnios and hemorrhagic amniotic fluid on placental MRI for SAH/SCH in risk stratification. STUDY TYPE: Retrospective. POPULATION: Seventy-one singleton pregnancies with SAH/SCH identified on placental MRI performed during the second or third trimesters, from 2016 to 2023. FIELD STRENGTH/SEQUENCE: 1.5 T, Fat-saturated T1-weighted gradient echo and half-Fourier-acquired single-shot turbo spin echo sequences. ASSESSMENT: Cases were classified into three groups: Groups A (oligohydramnios and hemorrhagic amniotic fluid), B (either oligohydramnios or hemorrhagic amniotic fluid), and C (SAH or SCH only). Groups B and C were subclassified as B-1 (oligohydramnios), B-2 (hemorrhagic amniotic fluid), C-1 (detected hematoma on ultrasound before MRI), and C-2 (incidentally detected hematoma on MRI). Unfavorable obstetric outcome (abortion or birth before 34 gestational weeks) and neonatal outcome (duration of neonatal intensive care unit [NICU] stay) were compared. STATISTICAL TESTS: Fisher's exact test, Kruskal-Wallis test, Mann-Whitney U test, and Kaplan-Meier analysis with Log-rank test. Significance was determined at p < 0.05. RESULTS: Unfavorable obstetric outcomes were significantly higher in Group A (11/12, 91.7%) than groups B (6/17, 35.3%) and C (9/42, 21.4%). Significant differences were found among the five subclassified groups, most notably between B-1 and B-2. The median duration of NICU stay was 87, 30.5, 0, 25, and 8 days in Groups A (n = 12), B-1 (n = 5), B-2 (n = 12), C-1 (n = 11), and C-2 (n = 31), respectively. Group A showed the worst neonatal outcomes. DATA CONCLUSION: MRI findings of oligohydramnios and/or hemorrhagic amniotic fluid in pregnancies with SAH/SCH are associated with adverse obstetric and neonatal outcomes, supporting risk stratification. EVIDENCE LEVEL: 4. TECHNICAL EFFICACY: Stage 5.