Risk of Hypophosphatemia Following Postpartum Anemia Treatment with IV Ferric Carboxymaltose, IV Ferric Derisomaltose, and Oral Ferrous Sulfate

<b>Objective</b>: To compare the effects of intravenous (IV) ferric carboxymaltose (FCM), IV ferric derisomaltose (FDI), and oral ferrous sulfate on hypophosphatemia in women with postpartum anemia. <b>Methods</b>: Single-centre, open-label, randomized trial. Women were randomly allocated to receive IV FCM, IV FDI, or oral ferrous sulfate. IV iron was infused in one or two doses (on days 0 and 7 postpartum), while ferrous sulfate once daily. Serum phosphate level was measured at enrollment and 6 weeks postpartum. Serum phosphate level and the proportion of women with hypophosphatemia were analyzed. The Kruskal-Wallis test was used for comparison of phosphate levels and the Chi-squared test for comparison of proportions (<i>p</i> < 0.05). <b>Results</b>: Three-hundred women with postpartum anemia (Hb < 100 g/L within 48 h postpartum) were included. Phosphate levels at six weeks postpartum did not differ between groups: 1.24 mmol/L (inter-quartile range (IQR) 1.10-1.35; equivalent to 3.84 mg/dL, IQR 3.41-4.19) in the FCM group, 1.23 mmol/L (IQR 1.09-1.35; equivalent to 3.81 mg/dL, IQR 3.38-4.19) in the FDI group, and 1.25 mmol/L (IQR 1.15-1.34; equivalent to 3.88 mg/dL, IQR 3.57-4.15) in the ferrous sulfate group (<i>p</i> = 0.86). The proportion of women with hypophosphatemia was similarly low in all three groups (3 (3.1%) vs. 2 (2.2%) vs. 2 (2.2%); <i>p</i> = 0.89). At six weeks postpartum, hemoglobin levels were slightly higher in both IV iron groups compared with oral iron, but the differences were small and unlikely to be clinically meaningful. <b>Conclusions</b>: Treatment of postpartum anemia with IV FCM, IV FDI, and oral ferrous sulfate had similar impact on phosphate levels and incidence of hypophosphatemia at six weeks postpartum.