Deregulated body weight homeostasis, obesity, and the metabolic syndrome are known to come about with greater frequency in individuals who underwent gestation in an obese mother. This suggests that events taking place in the prenatal period can be altered by a mother’s obesity, and that these alterations have a life-long adverse effect on body weight regulation in the offspring. Using a mouse model of diet-induced obesity during pregnancy we have characterised a number of changes to the development of both neurons and non-neuronal cells in the arcuate nucleus, a key area for the regulation of body weight homeostasis. Specifically, we have observed impaired AgRP neural circuitry formation, and an aberrant blood-brain barrier both before and after birth. Additional evidence suggests that this may come about through aberrant exposure of the developing arcuate nucleus cells to IL6, which is elevated in fetuses of obese dams. Such exposure appears to alter the normal expression of developmental genes whose function is to regulate axonal growth and guidance.