Objectives: Interleukin-6 (IL-6) is a cytokine produced by monocytes, fibroblasts, and endotherial cells. It has many physiological functions, such as stimulates B cell, T cell, and stem cell proliferation and induces the inflammatory acute phase proteins including CRP in hepatocyte. Recently IL-6 is regarded as a more sensitive marker of neonatal infection than CRP, but the physiological change of IL-6 in neonates is not well investigated. Since we have reported that CRP after birth elevates by the stress during birth process, purpose of the present study is to test the hypothesis that IL-6 elevates after birth as CRP change.

Materials and Methods: Thirty-two term neonates without any complications were studied. We separated them into two groups, stressed vaginal delivery (Group A, 16), caesarean section before labor (Group B, 16). We analyzed their cathecolamins, cortisols, pH and base excess (BE) of cord blood and IL-6, CRP. Five ml of cord blood are collected and plasma was stored at -40°C. Cathecolamin assays was performed using HPLC, and cortisol using RIA. Cord blood and capillary blood samples of the neonates by heal stick were collected at 0 (cord blood), 12, 24, 48, and 72 hours after birth for IL-6 assays using CLEIA and CRP assays using LPIA.

Results and Conclusion: IL-6 of both groups have showed apparent increment for 12hours after birth, and gradually decreased afterward. Peak of IL-6 occurred before that of CRP, which was 24≈ 48h after birth. The means of peak IL-6, CRP and the stress hormones were as follow. Group A: B [IL-6(pg/ml) 195.4: 31.4, CRP (mg/dl) 1.03: 0.16, Dopamin (pg/ml) 18.81: 13.93, Noradrenarin (pg/ml) 759.13: 559.73, Adrenarin (pg/ml) 77.69: 32.33, Cortisol(μg/ml) 25.13: 10.29, pH 7.30: 7.30, BE -4.85: -3.45]. All data of Group A were higher than those of B. Furthermore, there were significant correlations between the peak IL-6 and the stress hormones and CRP. These data proved that the stress during the birth process elevates IL-6 and IL-6 induces CRP in neonates. So serial IL-6 measurement for monitoring infection should be used while considering the degree of stress during birth.