The search was performed using combinations of several keywords: “Ornithine Transcarbamylase deficiency”, “pregnancy”, “transition”, “therapy”, “gene therapy”, “dietetic modifications”, “clinical outcome”, “mortality”, “acute decompensation”, “laboratory investigations” and “genetic counselling” with Boolean operators “AND” and “OR” for a thorough search. The gene discussed is OTC; the disease is hyperinsulinemic hypoglycemia, familial, 4.