Antenatal anemia increases the risk of receiving postpartum red blood cell transfusions although the overall risk of transfusion is low.

BACKGROUND: The objective was to determine if antenatal anemia is associated with postpartum red blood cell (RBC) transfusion.

STUDY DESIGN AND METHODS: Women who gave birth at a regional, tertiary care maternity hospital between December 1, 2015, and September 31, 2016, with a documented antenatal hemoglobin (Hb) concentration were included. Women were grouped into those who were either anemic (Hb < 11.0 g/dL) or nonanemic. The change in Hb concentration and RBC transfusion rates were compared between the anemic and nonanemic women, as well as by the mode of delivery (vaginal vs. Cesarean). To estimate the volume of blood loss in a normal delivery, the mean postpartum Hb concentration decrease for the not transfused women was calculated by subtracting the nadir postpartum Hb concentration from the antenatal Hb concentration and averaging these concentrations according to delivery route.

RESULTS: Of 8039 cases analyzed, 1562 (19%) had antenatal anemia and 6477 (81%) were nonanemic. Of the anemic women, 57 (3.6%) received an RBC transfusion compared to 49 (0.76%) of the nonanemic women (p = 0.0001; odds ratio, 4.97; 95% confidence interval, 3.38-7.31). Antenatal anemia was significantly associated with receiving an RBC transfusion regardless of mode of delivery for those who delivered vaginally (p = 0.0001) or by Cesarean (p = 0.0001) compared to those who were nonanemic. The mean postpartum Hb concentration decrease was 1.12 ± 1.12 g/dL for vaginal deliveries and 1.34 ± 0.21 g/dL for Cesarean deliveries in the not transfused women (p = 0.0001).

CONCLUSION: Although the overall rate of transfusion was low, antenatal anemia was significantly associated with receiving a postpartum RBC transfusion.