What are the possible causes of postpartum hemorrhage on day 9 after delivery?

Causes of Postpartum Bleeding 9 Days After Delivery

The most common causes of bleeding 9 days postpartum are retained products of conception (RPOC) and endometritis, with the specific etiology depending on mode of delivery—cesarean section increases endometritis risk while vaginal delivery is more associated with RPOC. 1, 2

Primary Etiologies by Mode of Delivery

After Cesarean Section

• Endometritis is the predominant cause, occurring in 80% of secondary PPH cases following cesarean delivery compared to 53.4% after vaginal delivery 3
• Uterine artery pseudoaneurysm is more common after cesarean section and represents a rare but life-threatening cause that can present with sudden, catastrophic bleeding 4, 3, 5
• Retained placental tissue occurs in only 10.8% of cesarean deliveries with secondary PPH 3

After Vaginal Delivery

• RPOC are more likely, occurring in 32.8% of secondary PPH cases after vaginal delivery versus 10.8% after cesarean 1, 3
• Subinvolution of the placental bed is characterized by widely distended, patent residua of uteroplacental arteries with only partial thrombotic occlusion 6, 7
• Endometritis still accounts for 53.4% of cases after vaginal delivery 3

Less Common but Critical Causes

Vascular Abnormalities

• Uterine artery pseudoaneurysm presents with intermittent, profuse bleeding and can cause rapid cardiovascular collapse 4, 5
• Subinvolution of placental bed vessels (vessel subinvolution) involves dilated "clustered" myometrial arteries partially occluded by thrombi of variable age 7
• These vascular causes are frequently underdiagnosed and require angiography for definitive diagnosis 4, 7

Other Etiologies

• Pelvic hematomas (bladder flap, subfascial, or perivaginal) may become infected and present with delayed bleeding 1, 2
• Uterine scar dehiscence after cesarean section, though difficult to distinguish from normal cesarean scar appearance 1
• Gestational trophoblastic disease (choriocarcinoma) is rare but appears as a hypervascular intrauterine mass and should be considered with elevated β-HCG 1

Diagnostic Approach Algorithm

Initial Clinical Assessment

• Examine for uterine firmness first—a firm uterus rules out atony and directs attention to other causes 8
• Perform thorough visual inspection of the genital tract for missed lacerations, particularly if there was prior cesarean section or inadequate prenatal care 8
• Verify complete placental delivery from the original delivery records 8

First-Line Imaging

• Transvaginal ultrasound with color Doppler is the initial imaging modality of choice 1
• Look for thickened endometrial echo complex (>8-13 mm) suggesting RPOC, though this overlaps with normal postpartum appearance 1
• The most specific ultrasound finding for RPOC is a vascular echogenic mass, though flow may not always be identified 1
• Color Doppler improves specificity and negative predictive value for detecting RPOC by identifying vascularity within thickened endometrium 1

Advanced Imaging When Ultrasound is Nondiagnostic

• CT with IV contrast in hemodynamically stable patients can localize bleeding sources and identify vascular complications including pseudoaneurysm 1
• Multiphasic CTA (noncontrast, arterial, and portal venous phases) has 97% accuracy for detecting active extravasation 1
• Angiography should be performed early when vascular abnormality is suspected, as it allows both diagnosis and therapeutic embolization 4

Critical Pitfalls to Avoid

• Do not assume endometritis based solely on fever and bleeding—obtain imaging to exclude pseudoaneurysm, as delay in diagnosing vascular causes can result in repeated catastrophic bleeding 5
• Do not rely on ultrasound alone to exclude pseudoaneurysm—serpiginous myometrial vessels on Doppler suggest the diagnosis, but CTA or angiography provides definitive visualization 1
• Do not perform blind uterine curettage for presumed RPOC without imaging confirmation—this can precipitate massive hemorrhage if a pseudoaneurysm is present 4, 5
• Recognize that RPOC can be difficult to differentiate from blood products even on multiphase CT, and correlation with clinical context is essential 1

Management Considerations at Day 9

• The median onset of secondary PPH is 12 days postpartum, making day 9 a typical presentation timeframe 3
• Obtain complete blood count, coagulation panel (PT/PTT, fibrinogen), blood group and screen, and β-HCG if gestational trophoblastic disease is suspected 9
• Activate massive transfusion protocol if blood loss exceeds 1,500 mL 9
• Administer tranexamic acid 1 g IV over 10 minutes within 3 hours of bleeding onset, as effectiveness decreases 10% for every 15-minute delay 9
• Consider early angiography with embolization for vascular causes, particularly when no single bleeding source is identified on physical examination 9, 4