Objectives: the present study aimed to investigate the factors affecting postpartum urinary retention after vaginal delivery.

Materials and Methods: This cross-sectional analytical study measured post-void residual (PVR) urine volume by ultrasound at most 15 minutes after the first urination after delivery. Women who had a PVR>150 mL without urinary symptoms were assigned to the postpartum covert urinary retention group. Data was analyzed with SPSS v. 22 software. The Chi-square and Mann-Whitney tests were used for quantitative and qualitative variables, respectively.

Results: In this study, 1120 patients had normal delivery at Ayatollahs Rouhani Hospital during from 21. January 2016 to 20 January 2017. Of them, 306 (29.4%) cases with urinary retention were allocated to the case group and 734 (70.6%) cases without urinary retention were allocated to the control group. The odds of urinary retention in women who had instrumental delivery were 30.19 times as in others (P=0.003). Instrumental delivery is a risk factor for urinary retention. The linear effect of total length of labor was also measured, and revealed every one-minute increase in total length of labor increases the odds of covert urinary retention by 1.008 times (P<0.001).

Conclusions: This study showed that various factors are involved in the incidence of urinary retention. Instrumental delivery, birth weight, gestational age, and other factors can each be a risk factor of urinary retention.