Blood loss in low-lying placenta: placental edge to cervical internal os distance of less vs. more than 2 cm

Objective: To reconfirm that a low-lying placenta, with placental edge-internal os distance of 0–4 cm, is a risk factor for blood loss during delivery, and to determine whether blood loss differs between edge-os distance of ≤2 cm vs. >2 cm. Methods: We compared total blood loss between 73 singleton pregnant women with edge-os distance of 0–4.0 cm vs. controls. We also compared total blood loss between pregnant women with distance of 0–2.0 cm (lower) vs. 2.1–4.0 cm (higher). Results: Total blood loss was significantly greater in women with placental edge-os distance of ≤4 cm than controls in both delivery modes. The lower group showed a significantly higher incidence of excessive hemorrhage during vaginal delivery (60 vs. 19%, P=0.046) and bled more (median 1240 vs. 860 mL, P=0.059) than the higher group. Although this did not reach statistical significance, the lower group more frequently bled antepartum, required emergent cesarean section, and delivered abdominally. Regression analysis showed no association between the amount of blood loss and the edge-os distance in both delivery modes. Conclusion: Pregnant women with edge-os distance of 2.1–4.0 cm are of highest level of concern as are women with 0–2.0 cm distance.