Magnetic resonance imaging of clinically stable late pregnancy bleeding: beyond ultrasound

Objectives. To compare the accuracy of magnetic resonance (MRI) and colour Doppler-ultrasound (US) in the diagnosis of late pregnancy bleeding and to assess the accuracy of the different MR sequences in visualizing the origin of haemorrhage. Methods. 42 patients in the third trimester of pregnancy underwent to US and MRI for the evaluation of painless vaginal bleeding. Multiplanar HASTE, True Fisp, 3D T1 GRE and sagittal DWI sequences were acquired. Two radiologists, blinded to the results of US, reviewed each case, resolving by consensus any discrepancy. Reference standards were surgical and pathological findings. Results. The reference standards identified 22 placenta previa, 11 placental abruptions (1 coincident with a placental chorioangioma), 1 thrombohaematoma and 1 fibroma with haemorrhagic degeneration. MRI identified correctly all these condition with an interobserver agreement of 0.955. DWI and T1 weighted sequences were statistically superior to Haste and True Fisp sequences in detecting the cause of bleeding (p<.001). US had 6 false negatives and 2 false positive results, its diagnostic accuracy resulting lower than MRI (p=.001). Conclusions. MRI accurately evaluates pregnancy bleeding with an excellent interobserver agreement and can grant new and additional data when US is negative.