Incidence of Atonic Postpartum Hemorrhage
Uterine atony accounts for more than 75% of all postpartum hemorrhage cases and is the leading cause of early PPH, which affects 2-3% of all deliveries in developed countries. 1
Overall PPH Incidence
- Postpartum hemorrhage complicates approximately 2.9% of all deliveries, with uterine atony responsible for 79% of these cases 2
- The incidence of PPH varies across populations from 1.2% to 12.5% depending on definitions and healthcare settings 3
- Severe PPH (defined as PPH requiring transfusion, hysterectomy, or surgical repair) occurs in 3.0 per 1000 deliveries 4
- In France, severe PPH (blood loss >1000 mL) occurs during 2% of deliveries 1
Temporal Trends
- The overall rate of PPH increased 27.5% from 1995 to 2004, primarily driven by increases in uterine atony 2
- Severe PPH rates doubled from 1.9 to 4.2 per 1000 deliveries between 1999 and 2008, with increases in both atonic and non-atonic PPH 4
- This rising incidence is not explained by changes in traditional risk factors, which account for only 5.6% of the increase 4
High-Risk Populations for Atonic PPH
History of previous severe PPH confers the highest risk, with an 8.97-fold increased odds of recurrence (95% CI: 5.25-15.33) 5
Specific Risk Factors for Atonic PPH:
- Multiple gestation: 2.8-fold increased risk (95% CI: 2.6-3.0) 2
- Prolonged labor and chorioamnionitis: 2.9-fold increased risk (95% CI: 2.5-3.4) 2
- Maternal age extremes (<20 or ≥40 years): 1.5-fold increased risk 2
- Cesarean delivery: 1.4-fold increased risk (95% CI: 1.3-1.5) 4
- Polyhydramnios, retained placenta, and antepartum hemorrhage are independent risk factors 2
Critical Clinical Context
The majority (61.2%) of women who develop severe atonic PPH requiring transfusion have no identifiable risk factors beyond maternal age and mode of delivery 2. This underscores that all deliveries require preparedness for managing uterine atony, regardless of apparent risk profile.