Pre-delivery risk factors for postpartum hemorrhage: a Danish retrospective cohort study

<title>Abstract</title> <p>Purpose The incidence of postpartum hemorrhage (PPH) is increasing in high-income countries. The objective of this study was to identify risk factors for PPH identifiable before delivery for use in preventive strategies. Methods Retrospective cohort study including singleton vaginal deliveries (≥ 22 + 0 gestational weeks) during a one-year period at a University Hospital in Denmark. The primary outcome was PPH ≥ 1,000 mL within the first 24 hours postpartum. Risk factors were categorized as maternal, obstetric, or delivery associated. Multivariable regression analysis was used to estimate adjusted odds ratio (aOR) with 95% confidence intervals (CI) for independent risk factors. Results Among the 3,122 included vaginal deliveries PPH occurred in 5.5% (N = 173). After adjusting for all covariates, fertility treatment (aOR 1.80; 95% CI 1.07–3.01), hypertensive disorders of pregnancy (aOR 3.83; 95% CI 2.02–7.27), labor augmentation (aOR 1.92; 95% CI 1.27–2.92) and clinically estimated birthweight ≥ 4,000g when admitted for labor (aOR 1.88; 95% CI 1.13–3.11) significantly increased the odds of PPH while precipitous labor (aOR 0.39; 95% CI 0.25–0.63) reduced the odds. Conclusion Among the identified risk factors, fertility treatment and clinically estimated birthweight ≥ 4,000g, could be considered included in clinical guidelines aiming to prevent PPH.</p>