Association of adverse outcomes with three-tiered risk assessment tool for obstetrical hemorrhage

Abstract

Guidelines promote stratification for the risk for postpartum hemorrhage among parturients, although the evidence for the associated differential morbidity among the groups remains inconsistent among published reports. Using the California Maternal Quality Care Collaborative schema modified by the American College of Obstetrics and Gynecology, we compared the composite maternal hemorrhagic outcome and the composite neonatal adverse outcome among singletons who were categorized after delivery by the researchers as low-, medium-, or high-risk for postpartum hemorrhage. We hypothesized that the composite outcomes would be significantly different among the individuals in the different 3-tiered categories. This was a retrospective cohort study of all singleton parturients with a gestational age of at least 14 weeks who delivered at a single site within 1 year. The composite maternal hemorrhagic outcome included any of the following: estimated blood loss ≥1000 mL, use of uterotonics (excluding prophylactic oxytocin) or Bakri balloon, surgical management of postpartum hemorrhage, blood transfusion, hysterectomy, thromboembolism, admission to the intensive care unit, or maternal death. The composite neonatal adverse outcome included Apgar score <7 at 5 minutes, birth injury, bronchopulmonary dysplasia, intraventricular hemorrhage, neonatal seizure, sepsis, ventilation > 6 hrs., brachial plexus palsy, hypoxic-ischemic encephalopathy, or neonatal death. Multivariable Poisson regression models with robust error variance were used to estimate the adjusted relative risks with 95% confidence intervals. Of the 4544 deliveries in the study period, 4404 (96.7%) met the inclusion criteria, and among them, 1745 (39.6%) were categorized as low, 1376 (31.2%) as medium, and 1283 (29.1%) as high risk. Overall, 941 (21.4%) participants experienced the composite maternal hemorrhagic outcome with 285 (16.4%) of those being in the low-risk group, 319 (23.2%) in the medium-risk group, and 337 (26.3%) in the high-risk group. Among all parturients, 95.7% in the low-, 89.4% in the medium-, and 85.3% in the high-risk group neither had an estimated blood loss or a quantified blood loss ≥1000 mL nor were transfused. After multivariable adjustment and when compared with the low-risk group, there was a significantly higher risk for the composite maternal hemorrhagic outcome in the medium-risk group (adjusted relative risk, 1.23; 95% confidence interval, 1.05-1.43) and in the high-risk group (adjusted relative risk, 1.51; 95% confidence interval, 1.31-1.75). Overall, 366 newborns (8.4%) developed the composite neonatal adverse outcome with 76 (4.2%) in of those being in the low-risk group, 153 (11.3%) in the medium-risk group, and 140 (11.1%) in the high-risk group. After multivariable adjustment and when compared with the low-risk group, there were no significant differences in the composite neonatal adverse outcome in the medium- (adjusted relative risk, 1.27; 95% confidence interval, 0.97-1.68) or the high-risk group (adjusted relative risk, 1.29; 95% confidence interval, 0.98-1.68). Although 8 of 10 parturients categorized as high risk neither had blood loss ≥1000 mL nor underwent transfusion, the risk stratification provides information regarding the composite maternal hemorrhagic outcome.