What are the definition, etiology, risk factors, and management of postpartum hemorrhage?

Postpartum Hemorrhage: Comprehensive Overview

Definition

Postpartum hemorrhage is defined as blood loss ≥500 mL after vaginal delivery or ≥1000 mL after cesarean section, OR any hemorrhage with signs/symptoms of hypovolemia within 24 hours of delivery, regardless of delivery route. 1, 2

• Primary (Early) PPH occurs within the first 24 hours after delivery and affects 1-5% of all deliveries, representing the most life-threatening form 1, 3
• Secondary (Late) PPH occurs from 24 hours up to 6-12 weeks postpartum and is less common but clinically significant 1, 3
• Blood loss is significantly underestimated by clinical estimation, particularly in vaginal deliveries—hemoglobin-based measurement is more accurate 4

Etiology and Risk Factors

The "4 T's" Framework for Causes

Tone (Uterine Atony) is responsible for >75% of all primary PPH cases and represents the single most important cause 1, 5

Trauma is the second most common category, including:

• Lacerations of the birth canal 1
• Uterine rupture 1
• Hematomas (bladder flap, subfascial, perivaginal) 1

Tissue causes include:

• Retained products of conception (RPOC) with or without infection 1, 5
• More common after vaginal delivery than cesarean 6

Thrombin (Coagulopathy) encompasses:

• DIC, amniotic fluid embolism, placental abruption 1
• Severe pre-eclampsia or HELLP syndrome 1
• Fibrinogen <2 g/L develops in 17% of cases with blood loss >2000 mL 1

Key Risk Factors

• Multiple pregnancy 7
• Lateral perineotomy (OR 2.8) 4
• Suturing by junior physician (OR 3.5) 4
• Prolonged third stage of labor 4
• Previous PPH (3.5-fold increased risk in subsequent pregnancies) 1

Immediate Management Algorithm

First-Line Actions (Within Minutes)

Administer tranexamic acid 1 g IV over 10 minutes PLUS oxytocin 5-10 IU (IV or IM) immediately—TXA must be given within 3 hours of birth as effectiveness decreases 10% every 15 minutes. 5

• Begin uterine massage and bimanual compression simultaneously 5
• Start fluid resuscitation with physiologic electrolyte solutions 5
• Administer oxygen to achieve arterial saturation ≥95% 5
• Warm all infusion solutions and blood products; use active skin warming (clotting factors function poorly at lower temperatures) 5

Second-Line Pharmacological Management (If Bleeding Continues)

• Second dose of TXA 1 g IV if bleeding continues after 30 minutes or restarts within 24 hours 5
• TXA should be administered regardless of PPH etiology (atony, trauma, retained tissue) 5
• Methylergonovine 0.2 mg IM ONLY if patient is normotensive—contraindicated in hypertension (>10% risk of severe hypertension) and asthma (bronchospasm risk) 5
• Avoid prostaglandin F2α in asthmatic patients due to bronchoconstriction risk 1, 5

Mechanical Interventions (Before Surgery)

Implement intrauterine balloon tamponade before proceeding to surgery or interventional radiology. 5

• Pelvic pressure packing effective for acute hemorrhage, can remain for 24 hours 5
• Non-pneumatic antishock garment for temporary stabilization during transfer 5
• Uterine compression sutures (B-Lynch or similar) if tamponade fails 5

Massive Transfusion Protocol

Initiate massive transfusion protocol if blood loss exceeds 1,500 mL—do NOT wait for laboratory confirmation of DIC. 1, 5

• Transfuse packed RBCs, fresh frozen plasma, and platelets in fixed ratios 5
• Target hemoglobin >8 g/dL and fibrinogen ≥2 g/L during active hemorrhage 5
• Re-dose prophylactic antibiotics if blood loss exceeds 1,500 mL 5

Definitive Interventions

Arterial embolization is particularly useful when no single bleeding source is identified, but requires hemodynamic stability for transfer 5, 3

• High clinical success rates with preserved post-embolization fertility 3
• Effective alternative to hysterectomy for patients desiring future fertility 3

Hysterectomy is reserved for hemorrhage refractory to all conservative measures 3

Diagnostic Imaging Approach

Early PPH (Within 24 Hours)

Transvaginal ultrasound with color Doppler is the primary imaging modality:

• Echogenic endometrial mass with vascularity is most diagnostic for RPOC 6
• Color Doppler detects swirling/yin-yang pattern in pseudoaneurysm 6
• Thickened endometrium up to 2-2.5 cm is nonspecific in early postpartum period 6

CT with IV contrast for hemodynamically stable patients:

• Localizes bleeding source, particularly for intra-abdominal hemorrhage 6, 5
• Detects bladder flap, subfascial, or perivaginal hematomas 6
• Hematomas >5 cm should raise suspicion for uterine dehiscence 6
• Small (<4 cm) subfascial and bladder flap hematomas may not be clinically significant 6

Late PPH (24 Hours to 6 Weeks)

• Ultrasound with Doppler to evaluate for RPOC, subinvolution of placental bed, or pseudoaneurysm 6, 1
• CT with IV contrast if vascular abnormalities or abscess suspected 6

Critical Pitfalls to Avoid

Do NOT delay tranexamic acid administration—it must be given within 3 hours of birth, and administration beyond 3 hours may be harmful. 5

Do NOT wait for laboratory results before initiating massive transfusion protocol when blood loss exceeds 1,500 mL. 1, 5

Do NOT use methylergonovine in hypertensive patients (>10% risk of severe hypertension) or asthmatic patients (bronchospasm risk) 1, 5

Do NOT use prostaglandin F2α in asthmatic patients due to bronchoconstriction risk 1, 5

Do NOT routinely perform manual removal of placenta except in cases of severe and uncontrollable PPH 5

Do NOT rely on clinical estimation of blood loss—it significantly underestimates actual blood loss, particularly in vaginal deliveries 4

Special Populations

Anticoagulated Patients

• Switch from oral anticoagulants to LMWH/UFH from 36 weeks gestation 5
• Discontinue UFH 4-6 hours before planned delivery 5
• If emergent delivery required on therapeutic anticoagulation, consider protamine (partially reverses LMWH) 5
• Cesarean delivery preferred to reduce fetal intracranial hemorrhage risk 5
• Active management of third stage with oxytocin is critical—primary hemostasis mechanism is myometrial contraction, not coagulation 5
• Women receiving therapeutic LMWH have 1.9-fold increased risk of PPH after vaginal delivery (OR 1.9,95% CI 1.1-3.5) 6

Patients with Mechanical Heart Valves

• Continue hemodynamic monitoring for at least 24 hours post-delivery due to significant fluid shifts that may precipitate heart failure 5
• Early ambulation with elastic support stockings reduces thromboembolism risk 5
• Consider thromboprophylaxis after bleeding controlled, especially with additional VTE risk factors 5

Complications

Immediate Complications (Within 24 Hours)

• Hypovolemic shock leading to tissue hypoxia and multiorgan failure 2, 8
• DIC (17% of cases with blood loss >2000 mL develop fibrinogen <2 g/L) 1
• Adult respiratory distress syndrome 2
• Acute renal failure 2

Early Complications (24 Hours to 6 Weeks)

• Endometritis or abscess formation, particularly with RPOC 1
• Bladder flap, subfascial, or perivaginal hematomas requiring intervention 1
• Ovarian vein thrombosis 1
• Sheehan syndrome (pituitary necrosis) 1, 2

Delayed Complications

• Vascular uterine abnormalities or pseudoaneurysm formation 1
• Subinvolution of placental bed 1
• Thromboembolic complications from immobility and coagulopathy 1
• 3.5-fold increased risk of recurrent PPH in subsequent pregnancies 1

Treatment-Related Complications

• Surgical complications including infection, poor wound healing, adhesion formation 1
• Non-target embolization from arterial embolization procedures 1
• Bronchospasm from prostaglandin F2α or ergometrine, particularly in asthmatic patients 1
• Respiratory depression from opioid analgesia 1
• Infection risk with uterine packing or balloon tamponade 1

Monitoring and Follow-Up

• Continue hemodynamic monitoring for at least 24 hours post-delivery 5
• Monitor for complications: renal failure, liver failure, infection, Sheehan syndrome 5
• Counsel patients about 3.5-fold increased risk of PPH in subsequent pregnancies 1