Risk factors for postpartum hemorrhage in a cohort of 6011 Italian women.

INTRODUCTION

Postpartum hemorrhage is responsible for 25% of maternal pregnancy-related deaths and it is the first cause of maternal morbidity and mortality worldwide.

OBJECTIVE

To define the prevalence of postpartum hemorrhage and associated risk factors after vaginal birth and to develop a risk model that improves postpartum hemorrhage prediction.

PATIENTS AND

METHODS

All women who underwent a vaginal delivery at the Obstetric Unit of a large University hospital in Milan (Italy) between July 2007 and September 2009 were enrolled. Postpartum hemorrhage was defined as ≥ 500 mL blood loss. A nomogram tailored to predict postpartum hemorrhage was developed, summarizing the impact of each covariate on the probability of postpartum hemorrhage.

RESULTS

6011 women were studied (24% had blood loss ≥ 500 mL and 4.8% ≥ 1000 mL). Nulliparity, episiotomy, retained placenta and high neonatal body weight were confirmed as risk factors for postpartum hemorrhage. The odds ratio of postpartum hemorrhage was 0.86 (95%CI 0.78-0.90) for each 1 gr/dL increase in ante-partum hemoglobin. An extensive internal validation of the developed nomogram demonstrated a good stability of the risk model.

CONCLUSIONS

Low ante-partum hemoglobin is a new potentially modifiable risk factor for postpartum hemorrhage. A nomogram to predict the probability of postpartum hemorrhage is now available for external validation.