Does previous cesarean section per se, especially its numbe increase the risk of allogeneic blood transfusion at cesarean section for placenta previa?

Objective: At cesarean section (CS) for placenta previa (PP), previous CS, especially multiple CS, is reported to be associated with massive bleeding. The authors attempted to determine which causes massive bleeding, previous CS per se or previous-CS-associated factors. The need for allogencic blood transfusion (BT) at CS was set as a marker representing massive bleeding. Materials and Methods: This retrospective cohort study involved all 326 patients with PP who delivered in one institute using the same management protocol. The authors evaluated the associations between the number of previous CS, maternal characteristics, and perinatal outcomes, and calculated the odds ratio (OR) for allogeneic BT according to the number of previous CS. Results: With an increasing number of previous CS, the following significantly increased: abnormally invasive placenta, anterior placentation, total previa, and ultrasound-detectable lacunae. The rates of allogencic BT for patients with previous CS of 0x, 1x, and >2x were 6% (16/273), 37% (14/38), and 60% (9/15), respectively (p < 0.001). On adjustment for anterior placentation, total previa, and lacunae, ORs (95% confidence interval) of allogeneic BT for previous CS 1x and >2x were 6.3 (2.5-16.4) and 11.4 (3.0-42.2), respectively, with CS Ox being referent. On analysis of 308 (326-18) patients excluding 18 with an abnormally invasive placenta, the adjusted ORs of allogeneic BT for CS 1 x and >2x were 3.5 (1.1-10.8) and 6.2 (1.1-37.3), respectively, remaining high. Conclusion: The number of prior CS, and, thus the previous CS per se, increases the requirement for allogeneic BT, irrespective of the presence/absence of an AT, anterior placentation, total previa, or lacunae. Management protocol of PP women with multiple CS should be adapted accordingly.