The effect of labor and delivery on white blood cell count

Objective: To explore post-partum white blood cell (WBC) count, and possible factors affecting it. Study design: Retrospective cohort analysis of 12 079 healthy women, delivering a singleton term fetus with an uncomplicated course of labor, delivery and puerperium. All women delivered in a single tertiary, university-affiliated medical center from 2009 to 2014. Student’s t-test, Mann–Whitney’s U-test, χ² test and ANOVA were used to compare between variables. Multiple variable analyses was performed to allow adjustment for potential covariates and confounders. The main outcome measures included post-partum WBC count and the difference in the post-partum versus ante-partum WBC count, in association to mode of delivery, type of analgesia, timing of cesarean delivery and perineal trauma. Results: The mean post-partum WBC count was 13.39 ±.24 × 10⁹/L (range 1.20–37.30 × 10⁹/L). There is a significant increase in the WBC after delivery (2.1 9 ± 3.33 × 10⁹/L) with significant differences according to mode of delivery (2.34 ± 3.48, 3.32 ± 3.69 and 1.6 0 ± 2.87 × 10⁹/L for spontaneous, assisted and cesarean deliveries. Multiple variables can affect post-partum leukocytosis, including: age, parity, gestational age, mode of delivery, type of anesthesia, timing of cesarean delivery in relation to labor onset and the extent of perineal trauma. Conclusions: Post-partum leukocytosis is a physiological phenomenon with a wide normal variation and multiple contributing factors. As a single parameter, post-partum leukocytosis should not prompt further work up.