How is high iron (hyperferremia) managed in pregnancy?

Management of High Iron (Hyperferremia) in Pregnancy

If hemoglobin exceeds 15.0 g/dL or hematocrit exceeds 45.0% during pregnancy, immediately discontinue all iron supplementation and investigate for poor blood volume expansion, as elevated hemoglobin/hematocrit is associated with serious adverse outcomes including fetal growth restriction, fetal death, preterm delivery, and low birth weight. 1

Recognition of High Iron States

The provided guidelines focus predominantly on iron deficiency rather than iron excess, but critical thresholds for concerning elevations are clearly defined:

• Hemoglobin >15.0 g/dL or hematocrit >45.0% indicates inadequate plasma volume expansion and warrants immediate attention 1
• Women with hematocrit ≥43% at 26-30 weeks' gestation face more than twofold increased risk for preterm delivery and fourfold increased risk for fetal growth restriction 1
• These elevated values represent a pathologic state rather than optimal iron status 1

Immediate Management Steps

Discontinue Iron Supplementation

• Stop all prenatal vitamins containing iron and any additional iron supplements immediately when hemoglobin exceeds 15.0 g/dL 1
• The standard prenatal vitamin dose of 30 mg elemental iron daily, while appropriate for most women, becomes harmful in those with elevated hemoglobin 2
• Higher supplementation doses (60-120 mg daily) used for treating anemia must be discontinued 2

Adjust for Confounding Factors

Before concluding true hyperferremia exists, account for physiologic variables:

• Altitude adjustment: Hemoglobin values should be adjusted upward by approximately 0.5-0.8 g/dL for women living above 3,000 feet elevation 1, 3
• Smoking status: Cigarette smoking causes a generalized upward shift in hemoglobin (0.3-0.7 g/dL depending on intensity), which can mask the true iron status 1, 4
• Race considerations: Black women may have lower baseline hemoglobin values than white women, though this represents normal variation 1

Investigate Underlying Causes

High hemoglobin/hematocrit in pregnancy suggests:

• Inadequate plasma volume expansion, which is the primary concern and predictor of adverse outcomes 1
• Excessive iron supplementation in women who entered pregnancy iron-replete 5, 6
• Underlying polycythemia or hematologic disorder requiring hematology consultation 3

Monitoring Strategy

• Recheck hemoglobin/hematocrit within 2-4 weeks after discontinuing supplementation to assess response 1
• Monitor fetal growth closely with serial ultrasounds given the established association between elevated maternal hemoglobin and fetal growth restriction 1
• Assess for hypertensive disorders of pregnancy, as high hemoglobin/hematocrit has been linked to hypertension in pregnancy 1

Prevention of Iron Excess

The evidence suggests a U-shaped risk curve, with both low and high iron status associated with adverse outcomes 5, 6:

• Individual iron prophylaxis based on serum ferritin is preferable to universal supplementation: ferritin >70 μg/L requires no supplements; ferritin 30-70 μg/L warrants 40 mg daily; ferritin <30 μg/L requires 80-100 mg daily 7
• In iron-replete populations (common in developed countries with fortified foods and adequate meat consumption), routine high-dose supplementation may cause harm 5, 6
• Minimum effective iron doses should be used to avoid negative effects on absorption of other divalent metals and increased oxidative stress 7

Critical Pitfalls to Avoid

• Do not continue routine iron supplementation when hemoglobin exceeds 15.0 g/dL, as the guidelines clearly identify this threshold as harmful 1
• Do not assume elevated hemoglobin represents "good iron stores"—it actually signals pathologic hemoconcentration and poor pregnancy adaptation 1
• Do not overlook altitude and smoking adjustments, as failure to account for these factors leads to misdiagnosis 1, 3, 4
• Do not delay intervention, given the strong associations with fetal death, growth restriction, and preterm birth 1