Defining the Limits of Postpartum Leukocytosis: A Retrospective Cohort Study

Abstract

There are established reference ranges for many laboratory values during pregnancy. Fewer studies exist regarding the expected white blood cell (WBC) count after delivery. The aim of this study was to determine appropriate postpartum leukocytosis in a diverse patient cohort. Patients who delivered a live fetus at 37 weeks or later were retrospectively identified. Complete blood counts collected on hospital admission and postpartum day one were used to quantify the change in WBC count associated with delivery. A total of 2245 patients were included; of these patients, 1476 delivered vaginally and 769 delivered via cesarean section. The average change in WBC count was 2.99 × 103/mm3. A WBC count of 20.19 × 103/mm3 defined the 95th percentile. The average rise in WBC count was 3.31 × 103/mm3 after vaginal delivery and 2.34 × 103/mm3 after cesarean section (p < 0.001). Patients with chorioamnionitis or endometritis had an average postpartum WBC rise of 7.38 × 103/mm3 compared to 2.99 × 103/mm3 in controls (p < 0.001). There was no difference in WBC count rise with comorbid asthma, diabetes, or chronic hypertension. A greater WBC count rise was found in patients with pregnancy-induced hypertension. This study provides reference values for the average rise in WBC count after delivery and the 95th percentile postpartum WBC count in a diverse, medically complex patient population with and without delivery complications. Our findings further highlight maternal medical comorbidities that may contribute to the degree of postpartum leukocytosis.