INTRODUCTION: Few studies have evaluated urine postvoid residuals (PVRs) and their risk factors during the post-partum (PP) period. The aim of this prospective study was to screen postvoid residuals in a cohort of patients in PP, and to identify the risk factors. MATERIALS AND METHODS: For three months, patients in PP were given an evaluation of their PVR (ultrasounds method) after a spontaneous urination. Clinical data as regards delivery were collected. RESULTS: One hundred and sixty-eight patients were included. Among them, 61% had a urine volume at the first urination over 500 mL, and 52% presented with a pathological PVR (PVR over 150 mL for a urine volume over 150 mL). The median PVR was 153.50 mL. The median volume of the first spontaneous urination was 400 mL. Among patients with a pathological PVR, the total duration of the labor and the duration of its second phase were significantly longer (P=0.003 and P<0.05, respectively), and the volume of the first urination was higher. Indwelling catheterization during the delivery decreased the volume of the first spontaneous urination (volume over 500 mL in 28% vs 72% of patients, P=0.017) but was not associated with a decreased PVR in non-pathological deliveries. Instrumental deliveries were associated with higher PVRs than caesarean or physiological deliveries (244 mL, 180 mL et 156 mL; P=0.033). A bacteriuria was not significantly associated with PVR (54% vs 49%, P>0.05). CONCLUSION: We were able to identify risk factors for PVR in the PP, such as the duration of labor, instrumental delivery and elevated volume of the first urination after delivery.