Administration of single-dose intravenous (IV) iron during the early second trimester of pregnancy reduced the incidence of low birth weight (LBW) infants and achieved nonanaemic status (NAS) at delivery, according to a study presented at SMFM 2025.

Maternal iron deficiency anaemia (IDA) remains a significant global health issue, often leading to an increased risk of adverse perinatal outcomes. Despite the widespread recommendation of oral iron as the first-line treatment in obstetric guidelines, maternal IDA rates remain above global targets, said Dr Rupsa Boelig from Sidney Kimmel Medical College, Thomas Jefferson University in Philadelphia, Pennsylvania, US.

Boelig and her team conducted a parallel, three-arm study involving 4,368 singleton pregnancies (between 14 and 17 weeks of gestation) with confirmed maternal IDA (defined as an Hb level of 7.0-9.9 g/dL). Participants were randomized to receive a single-dose infusion of IV ferric carboxymaltose (FCM; n=1,462) or ferric derisomaltose (FDM; n=1,456) or oral iron 65 mg BID (n=1,450). [SMFM 2025, abstract LB03]

According to the results, a lower incidence of LBW (<2,500 g) infants was observed in the IV FCM group than the oral iron group (25.2 percent vs 29.3 percent; relative risk [RR], 0.87), but not in the IV FDM group (29.1 percent vs 29.3 percent; RR, 0.98).

All treatment groups achieved similar rates of NAS (Hb ≥11 g/dL at 30?34 weeks or delivery) prior to delivery (73 percent [IV FCM], 73.1 percent [IV FDM], and 69.7 percent [oral iron]. However, patients who received IV iron had a significantly higher rate of NAS without needing additional nonstudy iron or blood transfusion than those on oral iron (68.7 percent [in each IV arm] vs 54.2 percent; RRs, 1.24 [FCM] and 1.25 [FDM]; p<0.0001 for both).

Furthermore, both IV arms had lower nonresponse (defined as <1 g/dL increased in Hb) rates than oral iron arms (22 percent [FCM] and 19.8 percent [FDM] vs 37.5 percent; RRs, 0.59 and 0.53, respectively).

In terms of safety, only one infusion-related serious adverse event was observed in the IV FCM group, and the patient recovered completely, said Boelig. However, 2 weeks postinfusion, 4.3 percent of patients in the FCM group experienced hypophosphatemia, while only 1.8 percent was reported in the FDM group.

Overall, the findings suggest that initial treatment of maternal IDA with a single-dose infusion of IV iron reduced the incidence of LBW infants, particularly with IV FCM, and reduced the need for additional iron or transfusion in patients who achieved NAS at delivery with both IV FCM and FDM treatments over oral iron, stated Boelig.

“Our study results support that IV iron should be considered for first-line treatment of moderate maternal IDA and that single-dose IV iron infusion is safe and effective in pregnancy,” she added.