Placenta previa: distance to internal os and mode of delivery.

OBJECTIVE: The purpose of this study was to relate the mode of delivery and outcomes in a cohort of cases of placenta previa that had the last transvaginal ultrasonographic scan <28 days before delivery.

STUDY DESIGN: Cases in which the placental edge overlapped the internal cervical (n = 42) underwent cesarean section delivery. Labor was allowed in those with placental edge to internal os distance of 1-10 mm (group 1, 24 women) and those with a distance of 11-20 mm (group 2, 29 women).

RESULTS: Rates of cesarean section delivery (75% vs 31%; odds ratio, 6.7; 95% confidence interval [CI], 2-22) and of bleeding before labor (29% vs 3%; odds ratio, 11.5; 95% CI, 1.6-76.7) were higher in group 1 than in group 2. Blood loss at delivery (662 +/- 466 mL vs 510 +/- 547 mL) and rate of severe postpartum hemorrhage (21% vs 10%; odds ratio, 2.3; 95% CI, 0.5-9.7) were similar in the 2 groups.

CONCLUSION: More than two-thirds of women with a placental edge to cervical os distance of >10 mm deliver vaginally without increased risk of hemorrhage.