Hypothesis: proposals for the management of a neonate at risk of hyperammonaemia due to a urea cycle disorder.

It is difficult to prevent hyperammonaemia in patients with urea cycle disorders that present in the newborn period. This is true, even if treatment is started prospectively because of an affected relative. We propose several additional measures that could be used in conjunction with conventional therapy to improve the metabolic control. Catabolism could be reduced by delivering the babies by elective caesarean section, by starting intravenous glucose immediately after delivery and, possibly, by using beta-blockers or octreotide and insulin. The effectiveness of sodium benzoate and sodium phenylbutyrate might be increased by giving phenobarbital to the mother before delivery and subsequently to the baby to induce the enzymes for conjugation. We would expect the proposed measures to reduce the risk of hyperammonaemia and to improve the outcome for these patients. They have not, however, previously been used in this context, so families would need to be counselled carefully and controlled studies should be undertaken.