Results: Of 57 qualifying deliveries, total previa was present in 38 patients (66.7%), and marginal or partial previa in 19 (33.3%). Median blood loss was 1,510 ml (interquartile range, 1,170–2,000 ml). PI distance was positively correlated with blood loss; measurements at 30 to 32 gestational weeks were more correlated than at 35 to 37 gestational weeks by ultrasonography. Moreover, MRI measurements at 33 to 34 gestational weeks were much more correlated than ultrasonography. There was also a positive correlation for PH.