Urea cycle enzymes deficiencies are rare metabolic disorders. Ornithine transcarbamylase (OTC) deficiency is the most common type. The syndrome results from a deficiency of the mitochondrial enzyme OTC which catalyses the conversion of ornithine and carbamoyl phosphate to citrulline. It shows X-linked inheritance and typically remains asymptomatic until late infancy or early childhood. The severity of the symptoms depends on the age of the patient and the duration of hyperammonemia. Female heterozygotes are more difficult to diagnose. They suffer from hyperammonemic periods which can be triggered by trauma, infections, surgery, childbirth, parenteral nutrition, and by the initiation of sodium valproate therapy. The prognosis of OTC deficiency is better for those with an onset after infancy, but morbidity from brain damage does not appear to be linked to the number of episodes of hyperammonemia that have occurred. However, early diagnosis and prompt initiation of ammonia-lowering treatment are essential for survival of these patients. This case presents a patient who was diagnosed with OTC deficiency following mental confusion during pregnancy.