For some comparisons, even though the median protein concentrations were identical (log2 fold change = 0) in the comparison groups, the Wilcoxon rank sum test returned a significant p-value (e.g. IL-1α: preterm labor with intra-amniotic infection vs preterm labor without either intra-amniotic inflammation or proven intra-amniotic infection in the internal compartment of vesicles Table 2). Here, IL1A is linked to chorioamnionitis.