Predictive value of the neutrophil-to-lymphocyte ratio for epidural labor analgesia-associated intrapartum fever: a retrospective single-center study.

Background: Studies have indicated that epidural analgesia increases the risk of maternal fever during labor, possibly due to non-infectious inflammation. The neutrophil-to-lymphocyte ratio (NLR) is a crucial indicator of inflammation, with a higher NLR potentially signaling worse patient adverse outcomes. The present study explores whether NLR has clinical predictive value for epidural analgesia-related maternal fever (ERMF).

Methods: A retrospective analysis was performed for 1602 women who voluntarily requested analgesia for epidural labor from January 2023 to June 2024. Univariate and multivariate logistic regression analyses were applied to identify the factors influencing intrapartum fever, and the association between NLR and ERMF was explored. The receiver operating characteristic (ROC) curve was used to assess the area under the curve (AUC) of NLR for intrapartum fever, and the nearest ascending index was utilized to determine the cut-off value.

Results: A total of 1602 parturients were included, of which 160 (10%) had intrapartum fever. Body mass index (BMI) (OR = 1.132, 95% CI: 1.027-1.246, P = 0.012), the duration of the first stage of labor (OR = 1.002, 95% CI: 1.001-1.003, P < 0.001), percentage of lymphocytes (OR = 1.205, 95%CI: 1.073-1.354, P = 0.012) and NLR (OR = 1.964, 95% CI: 1.462-2.639, P < 0.001) were independent risk factors for intrapartum fever. High NLR levels were associated with a higher incidence of ERMF at subgroups of ages < 35 years (OR = 1.343, 95%CI: 1.215-1.486, P < 0.001), ages ≥ 35 years (OR = 1.274, 95%CI: 1.105-1.468, P = 0.01), BMI < 24 kg/m (OR = 1.326, 95% CI: 1.176-1.495, P < 0.001), BMI ≥ 24 kg/m (OR = 1.515, 95%CI: 1.147-2.000, P = 0.003), first stage of labor < 600 min (OR = 1.466, 95%CI: 1.241-1.733, P < 0.001), and first stage of labor ≥ 600 min (OR = 1.257, 95%CI: 1.109-1.424, P < 0.001). Maternal NLR levels greater than 6.305 (AUC = 0.702, 95%CI: 0.634-0.768, P < 0.001) were good predicators of intrapartum fever.

Conclusions: High NLR is associated with EMRF, and NLR is a viable predictor of early identification of the occurrence of EMRF, which may be beneficial for pregnancy outcomes.