What is the purpose of collecting labs, including complete blood count (CBC), blood typing and cross-matching, coagulation studies such as prothrombin time (PT) and partial thromboplastin time (PTT), and labs to assess liver and kidney function, in a postpartum patient?

Purpose of Postpartum Laboratory Tests

Complete blood count (CBC) is collected to assess for anemia and blood loss, monitor hemoglobin/hematocrit levels, and evaluate platelet count which is crucial for clot formation in postpartum patients. 1, 2

Blood Count and Hemorrhage Assessment

• CBC provides essential information about blood loss through hemoglobin/hematocrit values, especially important as postpartum hemorrhage is a leading cause of maternal morbidity and mortality 1, 3
• Hemoglobin drop ≥2 g/dL or requiring transfusion of ≥2 units of RBCs is associated with significantly increased mortality risk, particularly in patients with cardiovascular disease 1
• Platelet count assessment is critical as platelets are necessary for clot formation and may be depleted during significant bleeding events 2
• Early detection of postpartum hemorrhage through objective blood loss measurement (such as calibrated drapes) combined with appropriate laboratory monitoring leads to better outcomes 3

Coagulation Studies

• Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT) are collected to evaluate the extrinsic/common and intrinsic/common coagulation pathways respectively 1, 2
• Coagulation studies help identify postpartum coagulopathy, which is characterized by decreased fibrinogen levels, altered clot breakdown, and low thrombin generation 4
• Fibrinogen level measurement is crucial as it's often the first coagulation factor to reach critically low levels during major bleeding 2
• Viscoelastic testing methods (TEG, ROTEM) may provide more rapid and comprehensive assessment of clot formation, strength, and breakdown than traditional coagulation tests 1, 2

Blood Typing and Cross-Matching

• Blood typing and cross-matching are performed to prepare for potential transfusion needs in case of significant postpartum hemorrhage 1
• Having type-specific or cross-matched blood available reduces delays in transfusion when needed for hemodynamic instability 1
• In massive hemorrhage protocols, O-negative blood may be used initially while awaiting type-specific or cross-matched blood 1
• Blood product administration strategies should be guided by laboratory results when possible, though treatment should not be delayed while awaiting results in severe bleeding 2

Liver and Kidney Function Tests

• Liver function tests assess for liver damage which may occur during pregnancy complications like preeclampsia or HELLP syndrome 1
• Kidney function tests evaluate renal perfusion and function, which may be compromised during significant hemorrhage 1
• Monitoring organ function is essential as postpartum hemorrhage patients are at risk for multiorgan damage due to hypoperfusion 1
• Acid-base status assessment through arterial blood gas analysis helps guide resuscitation efforts and monitor tissue perfusion 1

Important Clinical Considerations

• Routine postpartum CBC may not be necessary for all vaginal deliveries but should be performed when there are risk factors for excessive blood loss or patient symptoms 5
• Natural hematocrit recovery in uncomplicated postpartum patients shows an average increase of 8.19±3.09 points from discharge to follow-up (approximately 3 weeks later) 6
• Women with preexisting conditions like chronic hypertension, diabetes mellitus, or preeclampsia with severe features experience less hematologic recovery postpartum 6
• Visual assessment of blood loss should be combined with laboratory monitoring for optimal management of postpartum bleeding 1

Pitfalls to Avoid

• Do not rely solely on conventional coagulation tests (PT, aPTT) as they may not correlate well with clinical bleeding 2
• Never delay treatment while waiting for laboratory results in cases of severe bleeding 2
• Avoid underestimating blood loss, which is common with visual assessment alone; quantitative measurement techniques are more reliable 1
• Remember that traditional coagulation tests were not designed to monitor coagulopathy during active hemorrhage and may not reflect the dynamic clinical situation 2