IL13 and asthma: Maternal cytokine production levels have been shown to influence the development of the immune system, with higher maternal IFN-γ:IL-13 and IFN-γ:IL-4 ratios during pregnancy being associated with decreased risk for childhood asthma at the age of 5 (100) and a decreased IFN-γ:IL-4 ratio during the first trimester of pregnancy being associated with an increased risk of atopy (108).