IV iron supplementation, dosage, and timing in pregnancy: A single-institution review on a maternal transfusion reduction bundle

Background: Little is known about the effects of intravenous iron (IVFe) supplementation on maternal hemoglobin (Hb) by timing of infusion and dosage. Objective: To identify the association of IVFe timing and dose on pre-delivery Hb. Study Design: A retrospective cohort study of pregnant patients with iron deficiency anemia (IDA) who received iron sucrose (Venofer®) at our Level IV maternity care center following the implementation of a quality improvement (QI) transfusion reduction bundle from January 2020 to December 2023. The primary outcome was the association between IVFe timing and pre-delivery Hb. Secondary outcomes included the impact of IVFe dosage and infusion-to-delivery interval on Hb. Statistical analyses included paired t-tests, Mann-Whitney U tests, χ² tests, ANOVA, and post-hoc Tukey multiple comparisons (significance set at p < 0.05). Results: 295 patients were included. Mean age, BMI, and ferritin were 26.6 ± 6.3 years, 28.1, and 7.2 ± 7.8 μg/L, respectively. Mean GA for IVFe administration was 34 weeks. Two patients required intrapartum/postpartum red blood cell transfusions. A greater mean Hb difference (2.5 g/dL vs 1.3 g/dL), was observed with IVFe at <34 weeks compared to ≥34 weeks (p < 0.001). Higher IVFe doses were associated with increased pre-delivery Hb levels (p = 0.002) and a longer infusion-to-delivery interval (p = 0.049). The strongest Hb improvement was seen with latency from ≥6–8 weeks with doses >800 mg versus <2 weeks at doses ≤ 800 mg (increase of 2.6 – 3.1 g/dL, p < 0.0001). Conclusion: Substantial benefit is seen when IVFe is given in the early third trimester, especially with ≥6 weeks of latency and doses ≥800 mg.