Is an iron infusion recommended for a pregnant individual at 37/40 weeks gestation with iron deficiency anemia?

Iron Infusion at 37 Weeks Gestation for Iron Deficiency Anemia

If iron deficiency anemia is confirmed at 37 weeks gestation, intravenous iron infusion is the preferred treatment over oral iron due to the advanced gestational age and limited time for oral supplementation to be effective. 1, 2, 3

Clinical Context at 37 Weeks

• At 37 weeks, you are in the late third trimester with minimal time remaining before delivery 1
• Oral iron typically requires 4 weeks to demonstrate adequate response (hemoglobin increase ≥1 g/dL), which may extend beyond delivery 1
• The prevalence of iron deficiency increases significantly in the third trimester, affecting up to 29.5% of pregnant women 1

Treatment Algorithm

When to Choose IV Iron Over Oral Iron

Intravenous iron should be administered in the following situations: 2, 3

• Advanced pregnancy (such as 37 weeks) where rapid correction is needed before delivery 2
• Severe iron deficiency anemia (hemoglobin <8-10 g/dL depending on severity) 2, 3
• Intolerance to oral iron (gastrointestinal side effects) 2, 3
• Lack of response to oral iron therapy 2, 3
• Clinical need for rapid and efficient treatment 2

IV Iron Dosing

• For patients ≥50 kg: Ferric carboxymaltose 750 mg IV in two doses separated by at least 7 days, for a total cumulative dose of 1,500 mg per course 4
• Alternatively, 15 mg/kg body weight up to maximum 1,000 mg IV as a single dose per course 4
• For patients <50 kg: 15 mg/kg body weight IV in two doses separated by at least 7 days 4

Evidence Supporting IV Iron at Late Gestation

• IV iron significantly reduces rates of anemia at delivery compared to oral iron (40% vs 85%, p=0.039) 5
• Rates of hemoglobin <10 g/dL at delivery were significantly lower with IV iron (10% vs 54%, p=0.029) 5
• Modern formulations like ferric carboxymaltose have been studied in well-controlled trials in pregnancy and are preferred for safety reasons 2
• Anaphylactic reactions are extremely rare with non-dextran products 2

Important Caveats

Diagnostic Confirmation

• Confirm iron deficiency anemia before treatment with hemoglobin/hematocrit appropriate for gestational age plus low ferritin (<30 μg/L) 1, 2
• Remember that physiologic anemia of pregnancy (hemodilution) is normal and should not be confused with true iron deficiency anemia 1
• Serum ferritin is an acute phase reactant and may be falsely elevated during inflammation, potentially masking iron deficiency 1

Safety Monitoring

• Close surveillance during IV iron administration is recommended for all intravenous iron products 2
• Avoid extravasation as brown discoloration may be long-lasting 4
• Check serum phosphate levels in patients requiring repeat courses within three months 4

Alternative Diagnoses to Consider

• In women of African, Mediterranean, or Southeast Asian ancestry, mild anemia unresponsive to iron may indicate thalassemia minor or sickle cell trait 1
• If MCV is very low or anemia is macrocytic, further investigation beyond iron deficiency is needed 3

Guideline Discordance

There is notable disagreement between major organizations: 6

• CDC (1998) recommends screening and low-dose iron supplementation for all pregnant women 6
• ACOG recommends screening all pregnant women and treating iron deficiency anemia with supplemental iron 6
• USPSTF (2015) found insufficient evidence to assess the balance of benefits and harms of screening or supplementation 6

Despite USPSTF's equivocal stance, the clinical reality at 37 weeks with confirmed iron deficiency anemia favors treatment, particularly with IV iron given the time constraints before delivery 1, 2, 3