Clinical usefulness of white blood cell count after cesarean delivery

To examine changes in white blood cell (WBC) count after cesarean and estimate risk of postoperative infection.

We measured complete blood cell counts at admission and on postoperative day 1 for 458 women who had cesareans. Information from charts was abstracted, and definitions of infectious outcomes and fever were applied by three physicians masked to laboratory results. We examined changes in absolute and relative WBC counts by labor status. Likelihood ratios for postoperative infection were calculated for statistically distinct categories of percentage changes.

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 postoperative day 1 (P <.001) WBC counts than those who did not (n = 200). However, change in WBC count after cesarean relative to antepartum was similar for both 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 ratio for diagnosis of serious postpartum infection of 0. 5 (95% confidence interval [CI] 0.3, 0.8), the midlevel (n = 141) to a category-specific likelihood ratio of 1.7 (95% CI 1.2, 2.3), and the highest level (n = 11) to a category-specific likelihood ratio of 5.8 (95% CI 1.8, 18.7).

Labor influenced postcesarean WBC counts but did not obscure changes associated with infection. Information gained from changes in WBC counts can be used to assess risk of infection.