A single IV iron dose in pregnancy proved safe but no better than tablets
Two large African trials gave anaemic pregnant women intravenous ferric carboxymaltose or oral iron. Neither found less anaemia near term, or heavier babies, with the infusion.
In two large randomised trials in Africa, giving anaemic pregnant women a single intravenous dose of iron did not leave fewer of them anaemic near term than standard iron tablets, and did not increase their babies' birthweight [s1][s2]. The infusion was safe in both trials, and in the Nigerian study it corrected iron stores more completely than tablets — but that advantage did not translate into less anaemia or better birth outcomes [s2].
Anaemia affects an estimated 46% of pregnancies in Africa, and the World Health Organization recommends oral iron, but tablets are often poorly tolerated and adherence is low [s1]. A single intravenous dose of a modern formulation, ferric carboxymaltose, promised to sidestep that problem: one infusion delivers a large iron load at a single clinic visit. The two trials tested whether that convenience buys better outcomes. Largely, it did not.
The Malawi trial
REVAMP, an open-label trial in southern Malawi, enrolled 862 women with a singleton pregnancy of 13 to 26 weeks and capillary haemoglobin below 10.0 g/dL, randomly assigning 430 to ferric carboxymaltose (up to 1,000 mg given once) and 432 to standard care (60 mg of elemental iron twice daily for 90 days) [s1]. The co-primary outcomes were maternal anaemia at 36 weeks' gestation and birthweight [s1].
The infusion did not reduce anaemia at 36 weeks: 52% (179 of 341) of the intravenous-iron group were anaemic versus 57% (189 of 333) on oral iron (prevalence ratio 0.92; 95% CI, 0.81 to 1.06; P = 0.27) [s1]. Birthweight barely differed — a mean difference of −3.1 g (95% CI, −75.0 to 68.9; P = 0.93) [s1]. There were no infusion-related serious adverse events, and adverse events overall did not differ by treatment [s1]. The one point at which the infusion pulled ahead was transient: anaemia was significantly lower four weeks after treatment (prevalence ratio 0.91; 95% CI, 0.85 to 0.97), an edge that had faded by term [s1].
The Nigeria trial
IVON, an open-label trial across 11 facilities in Lagos and Kano, enrolled 1,056 women with haemoglobin below 10 g/dL at 20 to 32 weeks, assigning 527 to intravenous ferric carboxymaltose (20 mg/kg to a maximum of 1,000 mg) and 529 to oral ferrous sulphate (200 mg, containing 65 mg of elemental iron, three times daily to six weeks postpartum) [s2]. Its co-primary outcomes were anaemia at 36 weeks and preterm birth [s2].
The result echoed Malawi. Anaemia at 36 weeks affected 58% (299 of 517) of the intravenous group and 61% (305 of 503) of the oral group (risk ratio 0.95; 95% CI, 0.85 to 1.06; P = 0.36), and preterm birth occurred in 14% (73 of 518) versus 15% (77 of 513) (risk ratio 0.94; 95% CI, 0.70 to 1.26; P = 0.66) [s2]. Adverse events did not differ significantly [s2]. Where IVON parted from REVAMP was in iron stores: intravenous iron reduced iron deficiency more than oral iron did, and on that basis its authors recommended that intravenous iron be considered for anaemic pregnant women in Nigeria and similar settings [s2].
Why the infusion underdelivers
The gap between correcting iron stores and curing anaemia is the crux. In a malaria-endemic sub-Saharan setting, anaemia in pregnancy has many causes beyond a shortage of iron — infection prominent among them — so topping up iron, however efficiently, cannot fix the fraction of anaemia driven by something else [s1]. Both trials were funded by the Bill & Melinda Gates Foundation and were open-label, meaning participants and staff knew which treatment was given [s1][s2].
For the wider stakes of anaemia and other treatable conditions in pregnancy, see our coverage of the cardiometabolic burden behind US maternal mortality, and of the WHO's first global guidelines on diabetes in pregnancy.
What it means
A single iron infusion is convenient, safe and effective at replenishing iron, and IVON's iron-deficiency finding is a real point in its favour where stores matter [s2]. But neither trial found that swapping tablets for an infusion left fewer women anaemic at term or produced healthier births in these settings, which keeps oral iron the reasonable first-line option and cautions against treating the infusion as a shortcut [s1][s2].
What to watch
Whether trials in populations where anaemia is driven mainly by iron deficiency — rather than by malaria and other infections — show the birth-outcome benefits these two African trials did not.
This article describes trial evidence and is not medical advice. Decisions about treating anaemia in pregnancy belong with a clinician.
Sources
- Ferric carboxymaltose versus standard-of-care oral iron to treat second-trimester anaemia in Malawian pregnant women: a randomised controlled trial — The Lancet, 21 April 2023
- Intravenous versus oral iron for anaemia among pregnant women in Nigeria (IVON): an open-label, randomised controlled trial — The Lancet Global Health, 19 September 2024
Sources
- Ferric carboxymaltose versus standard-of-care oral iron to treat second-trimester anaemia in Malawian pregnant women: a randomised controlled trial — The Lancet , April 21, 2023
- Intravenous versus oral iron for anaemia among pregnant women in Nigeria (IVON): an open-label, randomised controlled trial — The Lancet Global Health , September 19, 2024
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