The objective was to study the incidence, risk factors, and outcome of pregnancies complicated by placenta accreta in our population. Retrospective analysis of all deliveries between the years 1990-2000, and identification of all cases of placenta accreta, defined by clinical or histological criteria. For comparison purposes we defined two sub-groups: (i) all cases that ended with severe outcome and (ii) all patients who had a previous event of placenta accreta in one or more of their previous deliveries. We evaluated the potential risk factors leading to these conditions. The SPSS software package was used for statistical analysis. Univariate and multivariate analyses were performed by stepwise logistic regression. The study covered 34 450 deliveries from which 310 cases of placenta accreta were diagnosed (0.9 per cent). The risk factors associated with placenta accreta were previous cesarean delivery (12 per cent), advanced maternal age, high gravidity, multiparity, previous curettage and placenta previa (10 per cent). Hysterectomy was performed in 11 patients (3.5 per cent) with one case of maternal death, whereas 21 per cent of the patients required postpartum blood products transfusion. Antenatal diagnosis of placenta accreta or percreta by ultrasound or MRI, was achieved only in eight of the cases. In the sub-group of 15 patients (4.8 per cent) with severe outcome, the only significant risk factors were increased parity (O.R. = 1.29, 95 per cent CI 1.056-1.585), anteriorly low placenta (O.R. = 6.1, 95 per cent CI 1.4-25.3) and repeated cases of caesarean sections (O.R. = 3.3, 95 per cent CI 0.9-12.5), whereas in the 49 (16 per cent) patients with repeated cases of placenta accreta the only significant risk factor was the number of deliveries (O.R. = 1.5, 95 per cent CI 1.0-2.2). Repeated cesarean delivery, high parity, and anteriorly low placental location are associated with severe outcome in case of placenta accreta. Women with repeated events of placenta accreta may have better outcome and a genetic factor may serve as a cause for this condition.