LAS VEGAS — Treating non-anemic iron deficiency (NAID) with iron and vitamin C raised third-trimester hemoglobin levels and reduced prenatal anemia, but it did not lower the rates of the condition at delivery admission, according to research presented at the Society for Maternal-Fetal Medicine (SMFM) 2026 Annual Pregnancy Meeting.

Starting iron earlier also reduced the need for additional supplementation in later trimesters, but the study was too small to determine effects on perinatal outcomes, said Bijal Parikh, an MFM physician at Saint Peter’s University Hospital in New Brunswick, New Jersey. Parikh completed the research as an MFM fellow at Stony Brook University Hospital in Stony Brook, New York.

NAID is defined as having a ferritin level < 30 µg/L and is predictive of iron deficiency. An estimated 42% of pregnant patients have the condition. Risks for anemia in pregnancy include many maternal and fetal morbidities including preterm birth, preeclampsia, need for a blood transfusion, and developmental delays in the infant.

Guidelines from the American College of Obstetricians and Gynecologists recommend pregnant patients be screened for anemia in the first trimester and again between 24 and 28 weeks of gestation. The guidelines also recommend iron supplementation and prenatal vitamins for those with iron deficiency anemia but note that the effects on perinatal outcomes are unclear.

Parikh and colleagues aimed to understand how NAID treatment affects hemoglobin values and incidence of peripartum anemia. They conducted a double-blind, randomized trial between 2022 and 2024, randomly assigning 132 women (average age, 31 years; 50.8% White) to receive either 65 mg of oral iron and 500 mg of vitamin C daily (n = 64) or a placebo (n = 68).

Any patient who developed anemia was prescribed additional oral iron or received intravenous (IV) iron if they did not respond to oral supplements.

Both groups took a daily prenatal vitamin that contained 27 mg of iron and 100 mg of a stool softener twice a day as needed for constipation. Primary outcomes were third-trimester hemoglobin levels and anemia diagnosis. At baseline, patients had an average hemoglobin level of 12.4 g/dL and ferritin level of 18.8 mcg/L in the first trimester, with an average BMI of 29.

The study excluded women who had first-trimester anemia, who had taken iron supplements within 3 months prior to pregnancy, had a history of iron overload or hypersensitivity, or had significant vaginal bleeding before enrollment. Those with HIV, lupus, inflammatory bowel disease, or previous bariatric surgery, among other conditions, were also excluded.

Third-trimester adherence was lower in the treatment group (61.9%) than in the control group (80%).

The treatment appeared to have an effect: In the third trimester, 28.3% of the treatment group and 46.9% of the control group were diagnosed with prenatal anemia (P = .03), whereas the treatment group had hemoglobin levels of 11.6 g/dL compared with 11 g/dL in the control group (P < .05).

Among treatment participants, 14.1% received an oral iron prescription compared with 29.4% of those in the control group. But rates of IV iron were low and did not differ between the groups. No significant differences were observed between the groups in secondary outcomes.

Diana S. Wolfe, MD, MPH, obstetric director of the Maternal Fetal Medicine/Cardiology joint program at Montefiore Einstein in New York City, said she was not surprised by the findings because all patients took prenatal vitamins that contained some iron.

“This study confirms that a low ferritin is not helpful to detect need for iron,” Wolfe said. “A full panel of iron studies and hemoglobin are recommended to detect need for iron supplementation. This study confirms the standard of care at current for obstetric patients.”

No external funding was noted for the study. Parikh and Wolfe reported having no disclosures. 

Tara Haelle is a science/health journalist based in Dallas.