Iron-deficiency anemia affects many pregnant women. For many years, oral iron has been the standard first-line treatment. It works, but it can take a long time to correct anemia, and stomach side effects can make it hard to take consistently. That’s pushed researchers toward a faster option: iron infusion during pregnancy, delivered directly into the bloodstream. Several major studies published in the past year tested that idea, though their results don’t all point in the same direction.
Why anemia is so common in pregnancy
Many pregnant women feel exhausted, pale, and short of breath, and then a blood test reveals low iron. Anemia affects roughly 37% of pregnant women worldwide, according to the World Health Organization. That’s about 32 million women in 2019 alone. In the United States, iron deficiency causes most cases. It shows up in 15% to 25% of all pregnancies. Iron deficiency and iron-deficiency anemia aren’t quite the same thing. Deficiency means depleted iron stores. Iron-deficiency anemia occurs when that deficiency leads to insufficient hemoglobin and red blood cells.
Pregnancy makes anemia more likely by design. A pregnant woman’s blood volume grows by 20% to 30%. Plasma expands faster than red blood cells can keep pace. That lowers the concentration of hemoglobin in the blood. Meanwhile, the body needs much more iron. It builds red blood cells for the mother, the placenta, and the fetus. When diet and supplements can’t cover that demand, anemia follows.
Pregnancy makes anemia more likely by design.
Untreated iron-deficiency anemia carries real risks. It’s linked to higher rates of low birth weight and premature birth, heavier blood loss during delivery, and lower resistance to infection. Severe, untreated anemia is also associated with maternal deaths.
Standard treatment for maternal iron deficiency
The first-line treatment and prevention of iron deficiency anemia during pregnancy is oral iron supplementation. The World Health Organization recommends iron and folic acid for pregnant women to prevent maternal anemia, puerperal sepsis, low birth weight, and preterm birth. Less consensus exists on treating iron deficiency without anemia or on providing iron to asymptomatic women during pregnancy.
Intravenous iron is another way to rapidly increase blood iron levels, and research on maternal iron infusion is growing. The 2024 Cochrane review compared oral iron to intravenous iron across 13 trials and nearly 4,000 pregnant women, mostly in India and Africa. The review combined results from several different IV drugs and compared them to several oral ones.
Across those trials, women given IV iron had meaningfully higher hemoglobin within weeks. They also had about 15% lower relative risk of still being anemic around birth. But the review found limited evidence for differences in maternal or infant outcomes.
Additional studies in the past few years have expanded our understanding of the impact of iron infusions during pregnancy.
The largest maternal IV iron clinical trial
The largest study is the RAPIDIRON trial, published in the American Journal of Obstetrics & Gynecology in August 2025. Researchers randomly assigned 4,368 pregnant women in India to one of three treatments, starting around four months into pregnancy. All had moderate iron-deficiency anemia. One group took daily oral iron pills. The other two got a single infusion, either ferric carboxymaltose or ferric derisomaltose.
Rupsa Boelig, MD, MS, a maternal-fetal medicine specialist at Thomas Jefferson University and a RAPIDIRON co-author, explained the deliberate timing in a MediBulletin article. “What’s unique about this study is that we did the iron intervention early in the second trimester,” she said. Iron needs rise sharply as pregnancy goes on. That makes early deficiency harder to correct.
Ferric carboxymaltose reduced the risk of a low-birth-weight baby: 25.2% of those babies were underweight, versus 29.3% on pills. That’s a modest effect: for roughly every 25 women treated with ferric carboxymaltose instead of pills, one fewer baby was born underweight. Ferric derisomaltose didn’t show this improvement. Resolution of anemia was not achieved except in a sensitivity analysis in which both iron infusion methods resulted in a higher incidence of resolving anemia without additional iron or blood transfusion.
The infusions were generally safe. Among the 2,905 women who received a single IV infusion, only one case of anaphylaxis occurred, and it resolved with standard treatment.
A clue about why infusions might act faster
A second paper, published in April 2026, dug deeper into the same RAPIDIRON participants, tracking young red blood cells called reticulocytes. Women given an infusion showed faster improvement in these markers, between 26 and 30 weeks of pregnancy. By six weeks after delivery, the difference had disappeared. Skipping gut absorption may explain why: the data suggest this lets bone marrow respond faster, though the study didn’t test whether that improves outcomes for mothers or babies.
Does the benefit show up outside India?
A smaller trial, published in Obstetrics & Gynecology in May 2026, tested ferumoxytol, a different IV iron drug, against oral iron. Researchers enrolled 80 pregnant women with iron deficiency anemia at a single U.S. hospital, starting between 24 and 34 weeks. Hemoglobin rose more with the infusion than with pills after four weeks. By delivery, 92.5% of the infusion group had resolved their anemia, versus 65% on pills. This echoes RAPIDIRON in a different country and drug, though 80 women isn’t enough to detect rarer outcomes like blood transfusion or bleeding.
Preventing anemia with oral iron and iron infusions
A trial called FAIR, published in The Lancet Haematology in January 2026, asked whether adding IV iron to standard oral iron supplements during pregnancy could prevent anemia and low birth weight from developing, rather than treat anemia already present. Researchers enrolled 600 iron-deficient, non-anemic pregnant women in Pakistan. One group got five doses of IV iron over two weeks plus oral iron prophylaxis; the other got oral iron alone. Results for the 462 women completing the study were striking. Twenty-three percent of the IV-iron group became anemic by delivery, versus 74% in the oral-iron-alone group. In the IV-iron group, maternal hemoglobin levels were higher. Babies were also far less likely to be born small for their gestational age.
Why more information on maternal iron supplementation is needed
Some recent studies found that iron infusions resulted in maternal benefits, such as increased hemoglobin and prevention of anemia, beyond those obtained with oral iron alone. Yet, differences in study design (including iron formulations, intervention timing, and anemia status of participants) influenced the diverse outcomes reported.
A hematologist’s published response to the FAIR trial emphasized the importance of vitamin B12 and folate deficiency, which can also cause anemia. Nutrient deficiencies need to be considered, as they may influence outcomes in iron supplementation studies. The critique also noted the importance of considering maternal health conditions and measuring outcomes like postpartum hemorrhage, transfusion, and child neurodevelopment. While research hasn’t identified a major new safety issue, the evidence isn’t large enough to rule out rare complications.
What would need to happen next, and what to do now
Currently, oral iron remains the standard first-line treatment for maternal iron deficiency according to the WHO and American College of Obstetricians and Gynecologists. Recent iron infusion trials, along with future research that carefully considers maternal and child outcomes and safety, may lead to modified treatment regimens for specific populations.
For a pregnant woman with iron-deficiency anemia today, IV iron is a promising option. This is particularly true for women who can’t tolerate oral iron or need their anemia corrected quickly. It hasn’t been proven to work better for everyone, and the specific drug used may matter more than expected. Ewelina Rogozińska, MSc, PhD, one of the Cochrane review’s authors, notes that symptoms of iron deficiency and anemia often overlap with other conditions— which is why it’s worth raising them with a doctor early. That’s a conversation for a prenatal care provider, not a choice to make alone.
See our web page and other news articles about iron deficiency.
