Clinical usefulness of white blood cell count after cesarean delivery

Objective: To examine changes in white blood cell (WBC) count after cesarea n and estimate risk of postoperative infection. Methods: We measured complete blood cell counts at admission and on postope rative day 1 for 458 women who had cesareans. Information from charts was a bstracted, and definitions of infectious outcomes and fever were applied by three physicians masked to laboratory results. We examined changes in abso lute and relative WBC counts by labor status. Likelihood ratios for postope rative infection were calculated for statistically distinct categories of p ercentage changes. Results: We excluded 60 women with chorioamnionitis. Of the remainder, 34 ( 8.5%) developed endometritis and three (0.8%) pneumonia. Women who labored before cesarean (n = 198) had higher antepartum (P < .001) and postoperativ e day 1 (P < .001) WBC counts than those who did not (n = 200). However, ch ange in WBC count after cesarean relative to antepartum was similar for bot h groups (P = .41), averaging a 22% increase. We grouped percentage changes into the following three levels: up to 24%, 25-99%, and at least 100%. The lowest level (n = 246) corresponded to a category-specific likelihood rati o for diagnosis of serious postpartum infection of 0.5 (95% confidence inte rval [CI] 0.3, 0.8), the midlevel (n = 141) to a category-specific likeliho od ratio of 1.7 (95% CI 1.2, 2.3), and the highest level (n = 11) to a cate gory-specific likelihood ratio of 5.8 (95% CI 1.8, 18.7). Conclusion: Labor influenced postcesarean WBC counts but did not obscure ch anges associated with infection. Information gained from changes in WBC cou nts can be used to assess risk of infection. ((C) 2000 by The American Coll ege of Obstetricians and Gynecologists.).