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Ornithine transcarbamylase (OTC) deficiency is the most common inborn error in the metabolism of the urea cycle with an incidence of 1 in 14,000 live births. Pregnancy can trigger potentially fatal hyperammonemic crises. We report a successful pregnancy in a 29-year-old primiparous patient with a known diagnosis of OTC deficiency since infancy. Hyperammonemic complications were avoided due to careful multidisciplinary management which included a detailed antenatal, intrapartum and postnatal plan. Management principles include avoidance of triggers, a low-protein diet and medications which promote the removal of nitrogen by alternative pathways. Triggers include metabolic stress such as febrile illness, particularly gastroenteritis, fasting and any protein loading. In our case the patient, in addition to a restricted protein intake, was prescribed sodium benzoate 4 g four times a day, sodium phenylbutyrate 2 g four times a day and arginine 500 mg four times a day to aid excretion of ammonia and reduce flux through the urea cycle.

Original publication




Journal article


BMJ Case Rep

Publication Date





Adult, Female, Humans, Hyperammonemia, Ornithine Carbamoyltransferase Deficiency Disease, Patient Care Team, Pregnancy, Pregnancy Complications