Chemical prenatal diagnosis for inherited organic acidemia

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We have studied the prenatal diagnosis for inherited organic acidemia such as propionic acidemia and methylmalonic acidemia using stable isotope dilution method. We established the normal value of methylcitrate and methylmalonate in amniotic fluid and maternal urine. Sixteen fetus at risk for methylmalonic acidemia (n=13) and propionic acidemia (n=3) were diagnosed prenatally. Three fetuses were diagnosed as methylmalonic acidemia and one as propionic acidemia. The above diagnosis was compatible with the results of enzyme activity, postnatal urinary organic acid analysis, and clinical findings. We also minimized the volume of amniotic fluid for measuring sample to 2ml. We also performed the prenatal therapy of a patient with vitamin B_<12> responsive methylmalonic acidemia during the last ten days of gestation with oral administration of vitamin B_<12>. In such occasion, monitoring of methylmalonic acid in maternal urines was an useful indicator for the efficacy of the treatment.Prenatal diagnosis by maternal urine will be indicated in (1) mother did not notice the pregnancy, (2) mother never wants amniocentesis, (3) mother missed suitable period for amniocentesis, (4) unreliable result of amniocentesis, and (5) reconfirmation of the former results. Stable isotope dilution method will be applicable for other inherited disorders of organic acid.