['Placenta accreta is one of the most devastating pregnancy complications. We sought to compare outcomes between women with placenta accreta when diagnosed antenatally or intrapartum, and to define predictors of the antenatal diagnosis.', 'Retrospective case-control study.', 'University teaching hospital.', 'Twenty-four women with placenta accreta diagnosed antenatally and 20 women discovered intrapartum.', 'Chart review of historical and delivery-associated variables. Rates were compared between the groups.', 'Placenta accreta diagnosed antenatally or intrapartum.', 'Women with antenatal diagnosis had a lower estimated blood loss of a median of 4500ml (range 100-15000ml) compared with 7800ml (range 2500-17000ml, p=0.012) and required fewer units of packed red blood cells transfused (median 7; range 0-27 compared with 13.5; range 4-31, p=0.026). Nineteen (79%) women diagnosed antenatally had balloon catheter occlusion carried out during the cesarean section. Five (21%) had the entire placenta left in situ. There was no difference in the rate of surgical complications or duration of hospitalization. The clinical diagnosis among women with antenatal diagnosis was more often placenta percreta (p=0.013). The risk factor profile of women with antenatal diagnosis of placenta accreta included higher gravidity (p=0.014) and parity (p<0.0001), history of cesarean section (p=0.004), and placenta previa in the current pregnancy (p<0.001).'] Does antenatal diagnosis of placenta accreta lead to reduced blood loss?