Do postpartum blood transfusions carry increased risk of transfusion reactions?

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Although blood transfusions can be a lifesaving measure for postpartum hemorrhage, adverse transfusion reactions (TRs) carry significant concerns. A recent study in Blood Advances investigated whether blood transfusions postpartum are accompanied by an increased risk for TRs compared with transfusions given to nonpregnant women.

Using data from the Swedish National Birth Registry, the authors linked women who gave birth at > 22 gestational weeks with the Stockholm Transfusion Database, which included information on blood components administered and whether TR events occurred in women who received blood transfusions postpartum. The authors included a control group of nonpregnant women who received blood transfusions during the study period. Because most nonpregnant women who receive blood transfusions are older than the pregnant population, only women younger than 51 years of age were included as controls. 

During the study period, 517,854 pregnancies occurred and were included in the analysis. Blood transfusions of ≥ 1 unit of red blood cells (RBCs) from the time of delivery to 7 days postpartum occurred in 11,842 pregnancies (2.3%). Among the 48,352 units of blood components transfused postpartum, 208 units (0.4%) were registered as having resulted in a TR. 

The authors found 96 women with a TR (79 per 1000) among the 12,183 who received ≥ 1 transfused unit of RBCs, plasma, or platelets. Among the 89,684 nonpregnant women who received a blood transfusion, 360 women reported a TR (40 per 1000). However, in cases with simultaneous transfusions of RBCs, plasma, and platelets, it was impossible to identify which component caused the TR.

The unique event of a TR linked to a RBC unit was reported in 78 of the 11,842 (0.7%) pregnant women receiving a RBC transfusion compared with 252 of the 69,087 (0.4%) nonpregnant women who had an RBC transfusion, indicating an 80% increased risk for a TR in women postpartum (OR 1.8, 95% CI 1.4-2.4). TR frequency was highest in women transfused with 1 unit of RBCs (5.5%, 21/385) and lowest in those transfused with 2 units of RBCs (0.3%, 23/7001). Among women who received massive transfusions (≥ 10 units of RBC within 24 hours), the TR rate was 1.9%.

Compared with outcomes in all pregnancies involving a blood transfusion, a documented TR was most common in women with preeclampsia, labor induction, placental complications, or a premature delivery at < 34 weeks. Age, smoking status, and number of previous deliveries did not increase the TR rate. In multivariate regression analysis, only preeclampsia, induced labor, and premature birth at < 34 weeks were significant factors (OR, 2.0; OR, 1.7; and OR, 1.7; respectively). 

Postpartum hemorrhage is the most frequent cause of maternal mortality and morbidity worldwide and blood transfusions are a generally safe treatment, but ob/gyns and their patients need to be aware of the increased though small absolute postpartum risk of TR.