Maternal undernutrition during pregnancy is a risk factor for cerebrovascular and cardiovascular diseases in adulthood. Hypoxia-inducible factor 1 alpha (HIF1α) plays an essential role in cellular hypoxic responses, and its increased expression is associated with cerebrovascular and cardiovascular diseases. However, it is not known whether maternal undernutrition influences HIF1α expression in the fetal brain. We therefore analyzed the expression levels of HIF1α and its downstream genes in the fetal brain (day 17.5 of gestation, 1-2 days before birth). Maternal undernutrition did not noticeably affect the fetal body and brain weights. Both HIF1α mRNA and protein levels were increased in the brain under maternal undernutrition, despite the absence of hypoxia, as judged by the staining profile with hypoxyprobe-1 that identifies hypoxic cells. Importantly, maternal undernutrition caused the accumulation of HIF1α protein in oligodendrocyte precursor cells at the subventricular zone, a site of neurogenesis in the fetal brain. Maternal undernutrition also increased the mRNA level of mammalian target of rapamycin (mTOR), which could increase the level of HIF1α protein under normoxia. Furthermore, microarray analysis revealed that expression levels of mRNAs for 10 HIF1α downstream targets, including enolase 1 and hexokinase 1, were increased in the fetal brain under maternal undernutrition. Thus, the biochemical consequence of maternal undernutrition is similar to that of mild hypoxia. In conclusion, maternal undernutrition induces the expression of HIF1α in oligodendrocyte precursor cells at the subventricular zone, and it also induces the expression of hypoxia-related genes in the fetal brain probably via activation of the mTOR pathway.