What is the differential diagnosis for postpartum fever?

Postpartum Fever Differential Diagnosis

The differential diagnosis for postpartum fever is dominated by endometritis, which should be suspected when fever >100.4°F (38.0°C) occurs on more than two occasions >6 hours apart after the first 24 hours of delivery, particularly when accompanied by uterine tenderness and foul-smelling lochia. 1, 2

Primary Infectious Causes

Endometritis (Most Common)

• Postpartum endometritis is the leading cause of postpartum fever, presenting as a multi-organism syndrome most commonly seen after unplanned cesarean section 1
• Clinical presentation includes:
  • High fever (≥101°F or >100.4°F on more than two occasions >6 hours apart) after the first 24 hours post-delivery and up to 10 days postpartum 1
  • Abdominal pain and uterine tenderness 2
  • Foul-smelling lochia 2
• Endometritis, wound infection, and pneumonia are significantly increased after cesarean section compared to vaginal delivery 1
• Risk increases 5-7 times after cesarean section performed after labor or membrane rupture compared to vaginal delivery 1

Wound Infection

• Occurs primarily after cesarean delivery 1
• Presents with fever, erythema, warmth, and tenderness at the incision site 3
• Risk factors include obesity, malnutrition, smoking, prolonged labor or membrane rupture 1

Urinary Tract Infection

• Common cause of postpartum fever, particularly after catheterization during labor 3
• May present with dysuria, frequency, or may be asymptomatic 3

Pneumonia

• Increased risk after cesarean delivery, particularly with general anesthesia 1
• Consider in patients with respiratory symptoms and fever 1

Vascular Complications

Septic Pelvic Thrombophlebitis/Ovarian Vein Thrombosis

• Uncommon but critical diagnosis that can cause persistent postpartum fever despite antibiotic therapy 4
• Should be suspected when fever persists despite appropriate antibiotic coverage for endometritis 3
• Can be complicated by pulmonary embolism, making early diagnosis essential 4
• Requires imaging (CT or MRI) for diagnosis 1, 4

Timing-Based Approach to Differential

Early Fever (First 24 Hours)

• Fevers <38.4°C (101.1°F) in the first 24 hours often resolve spontaneously without intervention 3
• Benign single-day fever occurs in 3.3% of vaginal deliveries, typically presenting earlier (4.0 hours postpartum) with lower maximum temperatures (38.2°C) 5
• Risk factors for benign fever include primiparity and use of uterine pressure catheter 5

Late Fever (>24 Hours to 6 Weeks)

• Most common causes are endometritis and retained products of conception (RPOC) 1
• Other considerations include:
  • Wound infection or dehiscence 1
  • Breast engorgement or mastitis 3
  • Deep vein thrombosis 3
  • Pelvic abscess 1

Less Common Infectious Causes

Atypical Organisms

• Mycoplasma hominis can cause postpartum fever and requires specific antimicrobial coverage (e.g., minocycline) 6
• Actinomyces species in patients with intrauterine devices (requires 7-day anaerobic culture) 1

Breast-Related

• Mastitis or breast abscess 3
• Typically presents with localized breast tenderness, erythema, and systemic symptoms 3

Non-Infectious Causes

Hematomas

• Bladder flap, subfascial, or deep pelvic hematomas 1
• May present with pain, fever, and palpable mass 1

Retained Products of Conception

• Can be difficult to differentiate from blood products on imaging 1
• Presents with persistent bleeding, cramping, and fever 1

Clinical Approach Algorithm

For fever >38.7°C (101.6°F) in first 24 hours OR >38.0°C (100.4°F) on any two of the first 10 days postpartum:

1. Perform thorough examination focusing on:

   • Uterine tenderness and lochia characteristics (foul odor suggests endometritis) 1, 2
   • Cesarean incision if applicable (wound infection) 1
   • Costovertebral angle tenderness (pyelonephritis) 3
   • Breast examination (mastitis) 3
   • Lower extremity examination (DVT) 3

2. Initial antibiotic therapy with anaerobic coverage should be started empirically for suspected endometritis 3

3. If fever persists despite 48-72 hours of appropriate antibiotics, consider:

   • CT or ultrasound to evaluate for abscess, hematoma, or RPOC 1, 3
   • Septic pelvic thrombophlebitis/ovarian vein thrombosis 4
   • Resistant organisms or atypical pathogens 6
   • Wound dehiscence or deep infection 1

Critical Pitfalls to Avoid

• Do not attribute persistent fever solely to atelectasis without excluding infectious causes 7
• Cesarean delivery increases infection risk substantially (5-7 fold), particularly when performed after labor onset or membrane rupture 1
• Low CD4+ counts in HIV-infected women significantly increase risk of postpartum infectious complications 1
• Diagnostic delay in ovarian vein thrombosis is common due to its rarity but can lead to life-threatening pulmonary embolism 4
• Failure to respond to initial antibiotics mandates imaging and consideration of non-endometritis causes 3, 8