Prenatal diagnosis and therapy for a patient with vitamin B12-responsive methylmalonic acidaemia.

The prenatal therapy is described of a patient with vitamin B12-responsive methylmalonic acidaemia during the last 10 days of gestation with oral administration of vitamin B12 (20 mg/day) given to a mother did not normalize her urinary excretion of methylmalonic acid (MMA), which was 14.5 mmol/mol creatinine at 32 weeks of gestation. Before delivery, the mother was excreting 18.9 +/- 3.3 mmol MMA/mol creatinine (mean value at 7 days after vitamin B12 therapy), as well as at 32-37 weeks of gestation with no therapy. After birth, the level of MMA in the infant's urine was remarkably elevated (500-700 mmol/mol creatinine); the level of MMA in maternal urine decreased dramatically after delivery. Compared with two previous reports, the length of administration was not sufficient to reduce maternal MMA excretion. In future, the length of the therapy, route of administration and total dose of vitamin B12 to maintain an efficient level of vitamin B12 in an affected fetus should be considered.