Increasing evidence suggests that normal vaginal delivery is
Increasing evidence suggests that normal vaginal delivery is a natural inflammatory process which results in increased levels of cytokines like Interleukin-6 (IL-6), Interleukin-8 (IL-8) in maternal and cord blood plasma . Increased levels IL-6 and IL-8 have been reported in the amniotic fluid of subjects who were delivered vaginally compared to those delivered by elective C-section. Existing data suggest that pre-labour elective C-section is associated with aberrant short-term innate immune responses such as reduced expression of inflammatory markers in the newborn infant , although TNF-a was reported to be increased .
Discussion The findings are consistent with previous studies which showed an increase in IL-6 levels in cord blood plasma of vaginal deliveries compared to elective C-section , . As for IL-8 expression, previous studies reported inconsistent results with no significant difference in two studies and increase in IL-8 in relation to labour events in another study , , . IL-8 is known to have neutrophil migration ability, which helps in enhanced chemotaxis . Lower neutrophils in C-section cord blood have been observed . The activation of cells through increased IL-8 during labour could be a biological DBU to prepare the newborn to face challenges ex-utero . In contrast to high IL-6, IL-8 levels in vaginally delivered cord blood plasma, a statistically significant increase in TNF-a in C-section cord blood plasma was observed. These results are not in line with previous studies which reported either no difference between C-section and vaginally delivered cord blood  or high levels of TNF-a in vaginally delivered cord blood . However, our study supports the results of Zanardo et al.  where the TNF-a levels are increased in C-section plasma levels. A significant new finding in our study is an increase in G-CSF in C-section compared to vaginally delivered cord blood plasma which has never been reported to date. One previous study has reported no difference between modes of delivery in the levels of G-CSF in cord blood, probably due to the study’s small sample size . It is important to note that some cord blood samples in vaginal and C-section deliveries show very low cytokine expression. However, more vaginal cord blood samples showed increased expression of IL-6 and IL-8 whereas more C-section cord blood samples show increased TNF-a and G-CSF expression. These differences between samples within each mode of delivery could be due to multiple factors like genetic differences, duration of labour, order of birth and labour intensity , , . Here, Bonferroni correction was used for multiple testing. IL-5, IL-2 and MCP1- initially showed differences but did not survive the correction for multiple testing. It is possible that the differences in the expression of these cytokines in the cord blood exist and could be demonstrated with a higher sample size. As indicated, many studies have been published demonstrating differences in cytokine expression in the cord blood plasma of vaginal and C-section births which may reflect the stresses that the newborn experiences during the process of birth , , . But the results are not always consistent. These inconsistencies could be due to the differences in the methods of cord blood collection, cytokine analysis, or maternal confounders such as anthropometric differences between studies. Most studies collect cord blood from the umbilical vein or mix cord blood from both artery and vein , . The study by Duncombe et al.  demonstrated differences in the levels of IL-6 and TNF-a in cord blood collected from the umbilical artery, umbilical vein and from the placenta, showing that blood from the umbilical vein shows the lowest level of reported cytokines. In our study, the cord blood was collected from the umbilical vein and despite that, significant differences between the four cytokines were observed.