What is the average blood loss during a normal vaginal delivery?

Average Blood Loss in Normal Vaginal Delivery

The average blood loss during a normal vaginal delivery is approximately 500 mL, with a median blood loss of 100-175 mL. 1, 2

Normal Blood Loss Ranges

• Median blood loss:

  • 125 mL (interquartile range 175 mL) 3
  • 100 mL (interquartile range 100-200 mL) 4
  • 171 mL (interquartile range 61-362 mL) in a large study of 104,079 deliveries 2

• Mean blood loss:

  • 180.1 mL (± 224.7 mL) 4

• 95th percentile:

  • 500 mL 4

Clinical Significance and Definition of Postpartum Hemorrhage

Postpartum hemorrhage (PPH) is formally defined as blood loss exceeding:

• >500 mL after vaginal delivery
• >1000 mL after cesarean delivery 1, 5

Based on quantitative blood loss measurements from a large multicenter study of 104,079 vaginal deliveries, the incidence of PPH was:

• 15.2% for blood loss >500 mL
• 3.4% for blood loss >1000 mL
• 1.0% for blood loss >1500 mL 2

Factors Affecting Blood Loss

1. Gestational age: Total blood loss is greater in pregnancies ≥37 weeks compared to <37 weeks 3

2. Length of third stage of labor:

   • Median length is 5 minutes (interquartile range 4 minutes)
   • Women with a third stage of labor ≥15 minutes have a significantly greater risk of blood loss >500 mL (relative risk 5.8) 3

3. Mode of delivery:

   • Cesarean sections have significantly higher blood loss (median 400 mL) compared to vaginal deliveries (median 100 mL) 4

4. Anticoagulation therapy:

   • Women receiving therapeutic-dose low-molecular-weight heparin (LMWH) have a higher risk of postpartum hemorrhage (30% vs 18% in non-users) after vaginal delivery 6
   • However, severe PPH (>1000 mL) rates are similar between LMWH users and non-users 6

Measurement Methods

Accurate measurement of blood loss is important for clinical management:

• Visual estimation tends to underestimate actual blood loss
• Quantitative blood loss (QBL) measurement is recommended over visual estimation 2
• In QBL measurement, approximately 60.6% of total blood loss is collected in drapes, with the remainder in sponges and other materials 2

Clinical Implications

• Early recognition of abnormal bleeding is crucial for preventing morbidity and mortality
• Systematic weighing of blood-soaked pads correlates with hemoglobin concentration drops and improves outcomes 1
• Point-of-care testing is preferred for monitoring coagulation status during obstetric hemorrhage 5
• Tranexamic acid should be administered if postpartum hemorrhage occurs, at an initial dose of 1 g 1, 5

Understanding normal blood loss parameters helps clinicians promptly identify abnormal bleeding patterns and initiate appropriate interventions to prevent serious complications.