Maternal obesity has significant consequences on the lifelong health of the developing child and rising global incidences make it one of the most common comorbidities during pregnancy. Offspring of obese mothers are at an increased risk of hospitalization for respiratory infections throughout childhood, which predispose these children to non-communicable respiratory diseases in later life. Animal models of maternal high fat diet (mHFD) feeding have observed common inflammatory outcomes with obesogenic models, but the effect on offspring varies with timing of the nutritional challenge and diet composition across studies. These studies demonstrate significant alterations to circulating and lung specific immune cells but the sequence of events that link maternal diet to these fetal outcomes are unclear, nor have they been tested in the context of a bacterial respiratory infection. Streptococcus pneumonaie is the most common causative pathogen of bacterial pneumonia and meningitis, making it of high clinical relevance. We aimed to investigate the effect of a mHFD (45% kcal from fat) during gestation and lactation, on offspring outcome and recovery from Streptococcus pneumoniae infection. Immunophenotyping, both before and after infection, revealed a hypo-inflammatory phenotype in circulating monocytes of the mHFD offspring with a decreased capacity to both initiate and terminate inflammatory responses. These offspring had significantly higher bacterial counts in lung tissues during infection and sustained cellular inflammation in survivors. In this thesis, we present foundational work on the detrimental influence of excess maternal nutrition on offspring immune function and infection outcomes, which may be involved in susceptibility to inflammatory and chronic disease in later life. A better understanding of this deep and lasting influence of the maternal environment will allow us to target preconception health as a form of harm reduction, informing stake holders and institutions to direct efforts towards DOHaD knowledge translation. / Thesis / Master of Science (MSc)