- Objective. To investigate pregnancy outcome in women suffering from idiopathic vaginal bleeding (IVB) during the second half of pregnancy. Methods. A comparison between patients admitted to the hospital due to bleeding during the second half of pregnancy and patients without bleeding was performed. Patients lacking prenatal care as well as multiple gestations were excluded from the analysis. Stratified analyses using the Mantel‐Haenszel technique and a multiple logistic regression model were performed to control for confounders. Results. During the study period, 173 621 singleton deliveries occurred at our institute. Of these, 2077 (1.19%) were complicated with bleeding upon admission during the second half of pregnancy. After excluding cases with bleeding due to placental abruption, placenta previa, cervical problems, etc., 67 patients were classified as having IVB (0.038%). Independent risk factors associated with IVB, using a backward, stepwise multivariable analysis were oligohydramnios (OR ¼6.2; 95% CI 3.1‐12.7; p50.001), premature rupture of membranes (OR ¼3.4; 95% CI 1.8‐6.2; p50.001), intrauterine growth restriction (IUGR, OR 5.6; 95% CI 2.5‐12.2; p50.001), and Jewish ethnicity (OR ¼1.9; 95% CI 1.0‐ 3.5; p ¼0.036). These patients subsequently were more likely to deliver preterm (537 weeks, 56.7% vs. 7.3%; mean gestational age of 33.6+5.7 weeks vs. 39.2+2.1 weeks; p50.001) and by cesarean delivery (CD, 35.8% vs. 12.1%, OR ¼4.0; 95% CI 2.4‐6.6; p50.001). Higher rates of low Apgar scores (57) at 1 and 5 minutes were noted in these patients (OR ¼10.3; 95% CI 5.9‐17.8; p50.001 and OR ¼17.8; 95% CI 7.1‐44.5; p50.001, respectively). Moreover, perinatal mortality rate among patients admitted due to idiopathic bleeding was significantly higher as compared to patients without bleeding (9.6% vs. 1.2%, OR ¼8.4; 95% CI 3.3‐21.2; p50.001). However, when controlling for preterm delivery, using the Mantel-Haenszel technique, the association lost its significance. Conclusion. Idiopathic vaginal bleeding during the second half of pregnancy is a risk factor for adverse perinatal outcome, mostly due to its significant association with preterm delivery. Careful surveillance, including fetal monitoring, is suggested in these cases in order to reduce the adverse perinatal outcome.