Is intravenous iron sucrose safe in pregnancy and what dosing schedule should be used for a pregnant woman with iron‑deficiency anemia (e.g., 70 kg, hemoglobin 9 g/dL)?

Intravenous Iron Sucrose Safety in Pregnancy

Yes, intravenous iron sucrose is safe in pregnancy after 13 weeks gestation, but should be avoided in the first trimester due to insufficient safety data. 1, 2

Timing and Safety Considerations

Avoid IV iron before 13 weeks gestation due to lack of safety data, and use oral iron supplementation during the first trimester instead. 3, 1

After 13 weeks gestation, IV iron sucrose has an excellent safety profile with no serious adverse effects reported in multiple randomized controlled trials involving pregnant women. 4, 5, 6, 7, 8

Key Safety Points:

• Resuscitation facilities must be immediately available during every infusion, as anaphylaxis can occur (though exceedingly rare at <1:200,000 administrations). 3, 2
• No test dose is required for iron sucrose, unlike iron dextran which carries a 0.6-0.7% risk of serious reactions and has been associated with 31 fatalities between 1976-1996. 3, 2
• Fetal monitoring during or after IV iron administration is not required and not recommended. 3, 1

Indications for IV Iron Sucrose

Consider IV iron sucrose in the second or third trimester when:

• Oral iron fails after 4 weeks despite confirmed compliance and absence of acute illness 1
• Hemoglobin is 7-10 g/dL and oral iron is poorly tolerated due to gastrointestinal side effects 2, 4, 5
• Rapid correction is needed in late pregnancy when time is limited 8

Dosing Protocol for Your Patient (70 kg, Hb 9 g/dL)

Each infusion delivers 200 mg of iron sucrose as a 10-minute IV bolus (this rapid administration is licensed and preferred over the older 2-hour infusion protocol). 3, 2

Calculating Total Iron Requirement:

For a 70 kg patient with hemoglobin 9 g/dL:

• Total iron deficit ≈ 1000-1500 mg 2
• This requires 5-8 infusions of 200 mg each 2
• Administer on alternate days until the calculated total is replaced 2, 7

The specific calculation: Hb deficit (g/L) × body weight (kg) × 0.3, plus an additional 10 mg/kg to replenish iron stores. 7

Efficacy Compared to Oral Iron

IV iron sucrose demonstrates superior efficacy:

• Hemoglobin rises 0.85 g/dL higher with IV iron sucrose compared to oral iron at treatment completion 6
• Mean hemoglobin increase of 5.1 g/dL vs 3.1 g/dL with oral iron at 30 days (p=0.002) 4
• Ferritin levels increase significantly more (mean difference 63.32 ng/mL, p<0.00001) 6
• 76% achieve hemoglobin ≥11 g/dL at delivery vs only 54% with oral iron 8

Adverse Effects Profile

IV iron sucrose has fewer adverse events than oral iron (risk ratio 0.50,95% CI 0.34-0.73, p=0.0003). 6

Common oral iron side effects include:

• 30% experience disturbing gastrointestinal symptoms 7
• 30% have poor compliance 7
• 6% cannot tolerate oral iron at all 7

IV iron sucrose side effects are mild and rare, with no major adverse effects reported in pregnancy studies. 4, 5, 7, 8

Post-Treatment Monitoring

• Do not check iron parameters within 4 weeks of IV iron administration, as circulating iron interferes with assays leading to spurious results. 1, 2
• Reassess hemoglobin 4 weeks after completing treatment, expecting an increase of ≥1 g/dL. 3
• Ferritin may not accurately reflect iron stores in inflammatory states, as it is an acute phase reactant. 3, 1

Alternative Formulation Consideration

Ferric carboxymaltose permits a single 1000 mg dose over 15 minutes, reducing the number of visits compared to iron sucrose. 3, 2 However, it is associated with treatment-emergent hypophosphatemia and should be avoided in patients requiring repeat infusions. 1 The cost is also substantially higher (£217.50 vs £70.80 per gram of iron). 2

Common Pitfalls to Avoid

• Never use iron dextran in pregnancy due to the significantly higher anaphylactic risk and reported fatalities. 3, 2
• Verify compliance with oral iron first before switching to IV therapy, as gastrointestinal side effects frequently lead to discontinuation. 1
• Do not rely on hemoglobin or hematocrit alone to diagnose iron deficiency in pregnancy, as physiologic hemodilution makes these measurements imprecise. 3, 1
• Ensure resuscitation equipment is immediately available during every infusion, even though serious reactions are rare. 3, 2