Background & objective: Severe asthma exacerbations during pregnancy are a common complication leading to poor health outcomes for both the mother and the baby. Asthma exacerbations are caused most frequently by respiratory viruses. A balance between antiviral and inflammatory immune responses is critical during pregnancy; the balance may be altered by asthma and respiratory virus infection. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from (i) non-pregnant healthy controls, (ii) pregnant non-asthmatics, (iii) post-partum non-asthmatics, (iv) non-pregnant asthmatics (v) pregnant asthmatics, and (vi) post-partum asthmatics. Cells were cultured in vitro with the mitogen phytohaemagglutinin or with a strain of the 2009 pandemic swine influenza. Interferon (IFN)-, interleukin (IL)-10 and IL-17 protein were measured from culture supernatant. Neutrophil counts were obtained in samples from pregnant and post-partum women. Results: Following the phytohaemagglutinin stimulation of PBMCs, pregnant asthmatics had significantly higher IL-17 and significantly lower IFN- responses compared with healthy non-pregnant women. Following infection with influenza, a significant reduction was also observed in IFN- and IL-10 production from PBMC of pregnant asthmatics. The IL-17 response to phytohaemagglutinin correlated with the neutrophil percentage. Differences in IFN-, IL-10 and IL-17 were found to persist for at least 6 months post-partum. Conclusions: A reduction in antiviral and regulatory immunity with increased inflammation during pregnancy occurs in PBMC from pregnant women with asthma. This novel information may relate to the increased susceptibility and disease severity to respiratory virus infections observed during pregnancy.