Single vs. two-unit transfusion in postpartum anemia: identifying predictors in a retrospective cohort

Obstetricians have debated the use of single or two-unit protocols in women presenting with post-partum anemia (PPA). A recent trial showed that implementing the single unit approach prevented second unit transfusion in 80% of patients. However, the risk factors for identifying patients who may benefit from up-front two-unit approach has yet to be defined.

Retrospective cohort study performed during 2013-2023. The study group included women with PPA who received transfusion of packed red blood cells (pRBCs). Patients who were hemodynamically unstable were excluded from the study. The groups were divided into patients who received single versus two units of pRBCs. The primary outcome was to identify risk factors that may benefit from an up-front two-unit protocol.

The final analysis included 368 women who received single-unit compared with 317 women receiving two-unit pRBCs. In univariate analysis, the duration of cesarean delivery (56.6 ± 35.8 vs. 45.5 ± 18.5 min, p = 0.0063), episiotomy during vaginal delivery, lowest postpartum mean Hb levels (6.6 ± 0.6 g/dL vs. 6.9 ± 0.5 g/dL, p = 0.0001) and mean delta of Hb levels (4.3 ± 1.5 g/dL vs. 3.9 ± 1.5 g/dL, p = 0.002) were significant risk factors for requiring two pRBCs compared to a single unit. Despite our findings, in a multivariate analysis, none of the risk factors was significantly associated with the two-pRBCs protocol.

In our cohort, no independent predictors for requiring two units were identified, highlighting the variability in clinical decision-making and supporting reassessment after each transfusion. Following these guidelines will help obstetricians reduce costs and morbidity associated with pRBCs transfusion.