Abstract / Summary
Introduction Early-onset neonatal sepsis (EONS) requires rapid diagnosis, yet the interpretation of white blood cell (WBC) and absolute neutrophil count (ANC) is complicated by physiological postnatal changes. While sex differences in neutrophil responses are known in older populations, limited data exist in neonates. This study aimed to investigate the kinetics of WBC and ANC in neonates with likely EONS and evaluate potential sex differences, including responses to antibiotic initiation. Methods We reviewed neonates treated at our center with antibiotics for likely EONS (suspected EONS with elevated CRP) between 2017 and 2022. WBC and ANC values were collected at standardized intervals before and after antibiotic initiation. Data were analyzed using piecewise linear mixed-effects regression models stratified by sex and timing of antibiotic initiation. Results Of the 506 neonates included, 304 (60.1%) were males and 202 (39.9%) females. Female neonates had higher ANC at birth (10,366 vs. 9,573 cells/ μ L, p = 0.012) and after antibiotic initiation (14,519 vs. 13,359 cells/μL, p = 0.042). During the first 12 h of life, ANC increased in both sexes (673 cells/μL/hour in females, 603 cells/μL/hour in males, p = 0.001), with no difference in rate. Among neonates treated at birth, WBC counts increased more rapidly in females (557 vs. 380 cells/μL/hour, p = 0.020). In contrast, neonates treated after birth showed a similar decline in WBC and ANC regardless of sex. Conclusion Female neonates with likely EONS consistently demonstrated higher ANC values and a more pronounced WBC increase in the early hours of life and after antibiotic initiation. This may reflect sex differences, potentially due to X-linked genes involved in the innate immune response. These findings support sex-specific interpretation of inflammatory markers in the evaluation of likely EONS evaluation and warrant further investigation into underlying immune differences.