What is the differential diagnosis and management for anemia in a postpartum patient?

Differential Diagnosis for Anemia Six Weeks Postpartum

Iron deficiency anemia is the most common cause of postpartum anemia at six weeks, accounting for approximately 79-90% of cases, and should be presumptively diagnosed and treated in otherwise well women. 1, 2

Primary Differential Diagnoses

Iron Deficiency Anemia (Most Common)

• Accounts for 79-90% of postpartum anemia cases and results from inadequate iron stores during pregnancy combined with blood loss at delivery 1, 2, 3
• Normal peripartum blood loss is approximately 300 mL, but losses exceeding 500 mL occur in 5-6% of deliveries and rapidly deplete iron reserves 2, 4
• Risk factors include anemia continuing through the third trimester, excessive blood loss during delivery, and multiple birth 1

Acute Blood Loss Anemia

• Postpartum hemorrhage (blood loss >500 mL) causes anemia in 5-10% of women 3
• Consider ongoing occult bleeding if anemia persists or worsens despite treatment 5

Infection-Related Anemia

• More common after cesarean section (11.8%) compared to vaginal delivery (0.36%) 3
• Infection and inflammation can cause blunted erythropoiesis even with adequate iron stores 2

Hemoglobinopathies

• In women of African, Mediterranean, or Southeast Asian ancestry, consider thalassemia minor or sickle cell trait if anemia is unresponsive to iron therapy after 4 weeks 1
• These conditions present with mild anemia that does not respond to standard iron supplementation 1

Nutritional Deficiencies (Less Common)

• Folate or vitamin B12 deficiency, though less prevalent than iron deficiency in the postpartum period 6
• Consider in vegetarian women or those with malabsorption 7

Diagnostic Approach

Initial Screening

• Screen women at risk at 4-6 weeks postpartum using hemoglobin or hematocrit 1
• Use nonpregnant anemia criteria: hemoglobin <120 g/L at 8 weeks postpartum 2, 4
• Confirm positive screening with repeat testing 1

Laboratory Evaluation

• For presumptive iron deficiency in otherwise well women, begin treatment immediately without extensive workup 1, 7
• If anemia fails to respond after 4 weeks of iron therapy (hemoglobin does not increase by ≥1 g/dL), obtain: 1
  • Mean corpuscular volume (MCV)
  • Red cell distribution width (RDW)
  • Serum ferritin (use cutoff of 30 μg/L for iron deficiency diagnosis) 6
  • Hemoglobin electrophoresis in at-risk ethnic groups 8

Critical Thresholds

• Hemoglobin <70 g/L requires urgent evaluation and possible transfusion 8, 7
• Hemoglobin 70-100 g/L warrants therapeutic iron supplementation 8, 2

Management Algorithm

Mild to Moderate Anemia (Hemoglobin 100-119 g/L)

• Prescribe oral elemental iron 60-120 mg daily 1, 7
• Counsel on iron-rich foods and absorption enhancers 1, 7
• Recheck hemoglobin after 4 weeks; expect increase of ≥1 g/dL 1

Treatment Failure After 4 Weeks

• Consider intravenous ferric carboxymaltose as first-line alternative due to rapid effectiveness and better tolerability 5, 9
• Iron sucrose (200 mg per dose over 10 minutes) is an alternative if ferric carboxymaltose unavailable 5
• Before switching to IV iron, confirm compliance with oral therapy and rule out hemoglobinopathies 5, 7

Severe Anemia (Hemoglobin <70 g/L)

• Intravenous iron 800-1500 mg should be considered as first-choice treatment 2
• Blood transfusion reserved for circulatory instability 2
• Administer IV iron in settings with resuscitation facilities available 5

Common Pitfalls to Avoid

• Do not perform extensive workup before initiating treatment in otherwise well women—presumptive diagnosis and immediate treatment is appropriate 1, 7
• Do not continue oral iron indefinitely without reassessment—failure to respond after 4 weeks mandates further evaluation 1
• Do not overlook ethnic-specific hemoglobinopathies in women of African, Mediterranean, or Southeast Asian descent with treatment-resistant anemia 1, 8
• Do not assume maternal anemia affects the newborn—the infant has independent compensatory mechanisms 3

Follow-Up Considerations

• Once hemoglobin normalizes, decrease iron supplementation to maintenance dose of 30 mg/day 1
• Continue monitoring for underlying causes if anemia persists, including occult bleeding or malabsorption 5
• Consider multidisciplinary involvement (gastroenterology, hematology) for complex or refractory cases 5