It is important to note that

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 glycosylase inhibitor 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 [18], [19], [20]. 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 [8], [12], [13]. 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 [10], [12]. The study by Duncombe et al. [16] 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. The methods used for cytokine analysis, such as ELISA or multiplex systems could also influence the concentrations of cytokines analysed. It is therefore crucial to use the same lot of the multiplex analysis kit to make such a comparison [21]. In our study, we ensured that the analysis was performed at the same time by the same lot of the multiplex kit. Previous studies looking at the difference between the modes of delivery have focused mainly on analysis of two to three cytokines [11], [22]. We analysed seventeen cytokines and identified four cytokines that showed significant differences even after the stringent Bonferroni correction for multiple testing. The limitation of this study is that the clinical protocols did not allow to assess the potential effect of medication on cytokine expression. All C-section delivered subjects received antibiotic prophylaxis and all mothers who delivered vaginally received prostaglandin E2. Prostaglandins are known to increase IL-8 [23], and it’s possible that the observed increase in IL-8 expression in our study is due to the use of prostaglandins. Morikawa et al. [24] showed a modulatory effect of antibiotics on cytokine production in vitro. Previous report has observed the influence of anesthesia on immune responses in newborns with maternal epidural anesthesia having less of an impact than general anesthesia [25]. Thus, we cannot exclude that some of the differences observed could be due to medication use and not due to the process of labour itself.