Neutrophil-to-lymphocyte ratio as an adjunct marker in maternal sepsis: a retrospective case-control study (2020-2025).

BACKGROUND

Early recognition of maternal sepsis is challenging because physiological changes of pregnancy reduce the diagnostic utility of conventional clinical and laboratory markers. The neutrophil-to-lymphocyte ratio (NLR), derived from a routine full blood count, has been proposed as a low-cost inflammatory marker, but its role in maternal sepsis remains unclear.

METHODS

We conducted a retrospective case-control study at a tertiary maternity hospital between January 2020 and December 2025. Women were allocated to one of three cohorts: confirmed maternal sepsis with bacteraemia, systemic inflammatory response syndrome (SIRS) without organ dysfunction and negative blood cultures, or healthy pregnant controls undergoing elective caesarean delivery. NLR was calculated from the first full blood count at the time of suspected infection or routine preoperative assessment. Between-group comparisons and associations with inflammatory biomarkers and clinical severity, including septic shock, were examined. Data is presented as median value with interquartile ranges [IQR].

RESULTS

One hundred and fifty women were included (50 per cohort). Median NLR was 15 [59] in confirmed sepsis, 13 [37] in SIRS, and 3 [5] in healthy controls (P < 0.001), demonstrating a graded increase across groups. Within the confirmed sepsis cohort, higher NLR correlated with procalcitonin (rs = 0.50, P < 0.01) and was associated with septic shock (OR 1.35, 95% CI 1.05-1.73; P = 0.02).

CONCLUSIONS

NLR is elevated in maternal sepsis and differentiates between sepsis, SIRS and healthy pregnancy. Its association with procalcitonin and septic shock supports its potential role as an adjunct marker of inflammatory burden. Further multicentre studies are required to define pregnancy-specific thresholds and evaluate its integration into maternal sepsis pathways.