Definition and classification

Definition & Quantification - More Than a Feeling

• Primary Definition (ACOG 2017): Cumulative blood loss (CBL) of ≥1,000 mL OR blood loss accompanied by signs/symptoms of hypovolemia within 24 hours of birth.
• Traditional Definitions:
  • Vaginal Delivery: >500 mL
  • Cesarean Delivery: >1,000 mL
• Quantification:
  • QBL (Quantitative Blood Loss): Formal measurement (weighing drapes/sponges). More accurate.
  • EBL (Estimated Blood Loss): Visual inspection. Notoriously inaccurate.
• Classification by Onset:
  • Primary (Early): Within the first 24 hours postpartum. (Most common)
  • Secondary (Late): Between 24 hours and 12 weeks postpartum.

⭐ Visual estimation of blood loss (EBL) is highly unreliable, often underestimating actual loss by up to 50%. This is why a shift to QBL is emphasized in modern protocols.

Classification & Etiology - The Usual Suspects (4 T's)

• Primary (Early) PPH: Blood loss within the first 24 hours postpartum.
• Secondary (Late) PPH: Occurs between 24 hours and 12 weeks postpartum.

📌 Mnemonic: The "4 T's" outline the primary etiologies, ordered by frequency.

• Tone (Uterine Atony) (~70-80%)

  • Most common cause. The uterus fails to contract adequately ("boggy" uterus).
  • Risk Factors: Uterine overdistension (macrosomia, multiples), prolonged labor, high parity, chorioamnionitis, tocolytic use.

• Trauma (~20%)

  • Lacerations of the genital tract (cervix, vagina, perineum), often after operative delivery.
  • Uterine rupture or inversion.
  • Hematoma formation (perineal, vaginal).

• Tissue (~5-10%)

  • Retained placental fragments (e.g., succenturiate lobe) or membranes.
  • Abnormal placentation (placenta accreta spectrum).
  • Retained blood clots.

• Thrombin (~1%)

  • Pre-existing or acquired coagulopathies that impair clot formation.
  • Examples: von Willebrand disease, ITP, HELLP syndrome, DIC (e.g., from placental abruption or amniotic fluid embolism).

⭐ Uterine atony is the single most common cause of PPH. In a patient with a soft, boggy uterus and continued bleeding after delivery, atony should be the primary diagnosis to address.

High‑Yield Points - ⚡ Biggest Takeaways

• Postpartum hemorrhage (PPH) is blood loss >500 mL (vaginal) or >1000 mL (cesarean).
• Clinically, it's any blood loss causing signs of hypovolemia.
• Primary PPH is within 24 hours postpartum; secondary PPH is from 24 hours to 12 weeks.
• Uterine atony is the leading cause of primary PPH (~80% of cases).
• Diagnosis relies on Quantitative Blood Loss (QBL), not visual estimation.
• Tachycardia is often the earliest sign of significant hemorrhage.