Iron deficiency in pregnancy, a condition closely tied to hemolytic disease of the fetus and newborn (HDFN) because both can affect a baby’s blood health and oxygen delivery, appears to be far more common than standard testing suggests, according to a study presented recently at the SMFM 2026 Pregnancy Meeting in Las Vegas, NV, February 8 to 13, 2026.
A prospective cohort study found that nearly all non-anemic pregnant patients screened at 24 to 28 weeks’ gestation had iron deficiency without anemia, raising questions about whether current screening practices are sufficient.
The study, conducted at Wake Forest University and Wake Forest University School of Medicine outpatient clinics, evaluated pregnant patients with hemoglobin levels of at least 11 g/dL at their initial prenatal visit. Participants underwent ferritin testing between 24 weeks 0 days and 28 weeks 6 days. Patients with prior anemia, known iron deficiency, malabsorptive disorders or multifetal gestation were excluded. Importantly, ferritin results were blinded to clinicians and did not guide care.
Iron deficiency without anemia was defined as ferritin less than 30 µg/L with hemoglobin of at least 11 g/dL. Among 321 patients who had ferritin measured, 66, or 20%, were anemic and excluded. Of the remaining 251 non-anemic patients, 240, or 94%, met criteria for iron deficiency without anemia.
Read more about symptoms and risks of HDFN
Baseline characteristics were largely similar between those with ferritin below 30 µg/L and those with higher levels. Patients with ferritin of at least 30 µg/L showed a trend toward higher rates of first pregnancy, 53% vs 34%, and tobacco use during pregnancy, 13% vs 5%, but these differences were not statistically significant. Maternal age, hemoglobin, mean corpuscular volume and rates of hypertensive disorders were comparable.
For patients, these findings suggest that a “normal” hemoglobin result may not guarantee adequate iron stores. Iron plays a critical role in oxygen transport and fetal development. Untreated iron deficiency can progress to anemia later in pregnancy, which has been linked to fatigue, increased risk of transfusion and possible adverse birth outcomes.
“Iron deficiency in pregnancy is exceedingly common, even among those with normal hemoglobin levels based on current ferritin criteria,” explained the authors of this study.
The authors suggested that routine ferritin screening or empiric iron supplementation may help prevent later anemia. The team plans to assess whether midtrimester ferritin levels predict hemoglobin at delivery admission and other perinatal outcomes. The findings also raise the possibility that ferritin cutoffs used to define iron deficiency in pregnancy may need to be updated.
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