The aim of this study was to characterize a novel assay to assess for the transplacental passage of functional cytokines, and to use this technique to assess for passage of the pro-asthmatic/pro-inflammatory cytokines interleukin 4 and 13 (IL-4 and IL-13) previously implicated in maternal transmission of asthma risk [10], [12]. This evidence concerns the gene IL4 and asthma.