The length of the third stage of labor and the risk of postpartum hemorrhage

OBJECTIVE: To estimate whether the length of the third stage of labor is correlated with postpartum hemorrhage. METHODS: In this prospective observational study women delivering vaginally in a tertiary obstetric hospital were assessed for postpartum hemorrhage. All women were actively managed with the administration of oxytocin upon delivery of the anterior shoulder. Blood loss was measured at each delivery in collecting devices, and drapes and sheets were weighed to calculate the blood loss at each vaginal delivery. Postpartum hemorrhage was defined as more than 1,000 mL blood loss or hemodynamic instability related to blood loss requiring a blood transfusion. RESULTS: During a 24-month period there were 6,588 vaginal deliveries in a single tertiary obstetric hospital, and postpartum hemorrhage occurred in 335 of these (5.1%). The median length of the third stage of labor was similar in women having and those not having a postpartum hemorrhage. The risk of postpartum hemorrhage was significant at 10 minutes, odds ratio (OR) 2.1, 95% confidence interval (CI), 1.6-2.6; at 20 minutes, OR 4.3, 95% CI 3.3-5.5; and at 30 minutes OR 6.2, 95% CI 4.6-8.2. The best predictor for postpartum hemorrhage using receiver operating characteristic curves was 18 minutes. CONCLUSION: A third stage of labor longer than 18 minutes is associated with a significant risk of postpartum hemorrhage. After 30 minutes the odds of having postpartum hemorrhage are 6 times higher than before 30 minutes. LEVEL OF EVIDENCE: III.