Glycogen storage disease type Ia (GSD Ia) leads to disturbed glycogenolysis and gluconeogenesis due to a deficiency in the enzyme glucose-6-phosphatase. A patient with GSD Ia showed hypoglycemia and proteinuria without dietary management since early pregnancy. The patient's condition was complicated by hypertension with increase in proteinuria at 22 weeks of gestation. In spite of administration of antihypertensive drugs and dietary management, the disease became more severe with deterioration in the fetal status and inhibition of fetal growth. Thus, a cesarean section was performed at 26 weeks of gestation. The delivered male infant weighing 412 g died at 2 days after birth. The patient's blood pressure had normalized within 3 months after delivery, while proteinuria persisted.