What is the cause of persistent low hemoglobin levels in a postpartum patient after a lower segment cesarean section?

Persistent Postpartum Anemia After LSCS: Diagnostic Approach

The most likely cause of persistent low hemoglobin on day 5 post-LSCS, despite resolution of AKI, thrombocytopenia, and hypoalbuminemia, is ongoing occult blood loss from retained products of conception, uterine atony with delayed hemorrhage, or an unrecognized thrombotic microangiopathy (TMA) such as atypical hemolytic uremic syndrome (aHUS) that is causing hemolysis rather than bleeding.

Immediate Diagnostic Workup Required

You must urgently differentiate between ongoing blood loss versus hemolytic anemia as the cause:

Laboratory Tests to Order Now

• Peripheral blood smear looking specifically for schistocytes (fragmented RBCs) which indicate microangiopathic hemolysis 1
• Direct Coombs test to exclude autoimmune hemolysis 1
• Haptoglobin level (will be low if hemolysis is occurring) 1
• LDH level (elevated in hemolysis and TMA) 1
• Reticulocyte count to assess bone marrow response 1
• ADAMTS13 activity level if TMA is suspected 1
• Fibrinogen level (should be 4-6 g/L in postpartum; <2 g/L suggests consumptive coagulopathy) 2

Clinical Assessment Required

• Measure cumulative blood loss using volumetric techniques - visual estimation consistently underestimates actual loss 3
• Pelvic ultrasound to exclude retained products of conception, hematoma formation, or ongoing bleeding 4
• Calculate Shock Index (heart rate ÷ systolic BP): >1 indicates hemodynamic instability requiring immediate intervention 3
• Examine for ongoing vaginal bleeding, uterine tenderness, or signs of infection 3, 4

Most Likely Diagnostic Scenarios

Scenario 1: Occult Ongoing Blood Loss (Most Common)

If schistocytes are absent and haptoglobin is normal:

• Average post-cesarean hemoglobin drop is 1.5 g/dL, but can be much higher with complications 5
• Blood loss >1000 mL occurs in 5-10% of cesarean sections and is frequently underestimated 6
• Retained products of conception are high-risk in post-LSCS patients due to weakened cesarean scar 4
• Delayed uterine atony or concealed hematoma formation can cause persistent anemia 6

Management approach:

• Transvaginal ultrasound with color Doppler to identify vascular retained tissue 4
• If RPOC confirmed, schedule surgical removal with blood products available, using ultrasound guidance to avoid uterine perforation at scar site 4
• Consider prophylactic tranexamic acid 1 g IV before procedure 4

Scenario 2: Thrombotic Microangiopathy (Critical to Exclude)

If schistocytes present, LDH elevated, and haptoglobin low:

The triad of hemolytic anemia, thrombocytopenia, and elevated LDH in the postpartum period mandates urgent TMA investigation 1. The key distinction:

• HELLP syndrome typically resolves within 72 hours postpartum 1
• Atypical HUS should be suspected when thrombocytopenia and hemolysis persist or worsen beyond 72 hours postpartum, especially with renal involvement (which you had - the AKI) 1
• TTP presents with ADAMTS13 activity <10% and neurological symptoms 1

Critical management decision:

• If thrombocytopenia is worsening beyond day 5, with persistent hemolysis despite "resolved" labs, initiate complement blockade with eculizumab immediately for presumed aHUS 1
• aHUS has high mortality without complement blockade but excellent outcomes with eculizumab 1
• Do NOT transfuse platelets in TTP unless life-threatening bleeding 1
• Urgent hematology and nephrology consultation required 1

Transfusion Decision Algorithm

Based on current hemoglobin level:

• Transfuse if Hb <7.0 g/dL regardless of symptoms 3
• Consider transfusion if Hb 7.0-8.0 g/dL with cardiac disease or ongoing bleeding 3
• Transfuse one unit at a time and recheck hemoglobin before each subsequent unit 3
• Each unit should increase Hb by approximately 1 g/dL 3

Iron Replacement Strategy

If bleeding/hemolysis excluded and anemia is purely dilutional or iron-deficiency:

• Severe anemia (Hb <8 g/dL): Intravenous ferric iron 800-1500 mg is first choice for rapid correction 7
• Mild-moderate anemia (Hb 8-10 g/dL): Oral ferrous iron 100-200 mg daily, with hemoglobin recheck in 2 weeks to confirm response 7
• Postpartum anemia is defined as Hb <11 g/dL at 1 week and <12 g/dL at 8 weeks postpartum 7

Critical Pitfalls to Avoid

• Do not assume anemia is simply "expected" post-cesarean - persistent low Hb on day 5 with resolved other parameters suggests an ongoing process 3, 1
• Do not miss aHUS - the combination of AKI + thrombocytopenia + anemia should trigger TMA workup even if labs have "improved" 1
• Do not delay ultrasound - retained products are high-risk in prior cesarean patients and require prompt diagnosis 4
• Do not rely on visual blood loss estimation - it consistently underestimates and delays intervention 3

Monitoring Plan

• Recheck hemoglobin in 4-6 hours or sooner if clinical deterioration 3
• Serial vital signs every 1-2 hours for first 24 hours 3
• Monitor urine output - oliguria may indicate ongoing hypovolemia or TMA progression 3
• Repeat peripheral smear and LDH if hemolysis suspected 1