Methylcitrate in maternal urine during a pregnancy with a fetus affected with propionic acidaemia.

Patients homozygous for propionic acidaemia have high levels of methylcitric acid in urine while heterozygotes have normal levels. Methylcitric acid was determined by stable isotope dilution gas chromatography-mass spectrometry in maternal urine during a pregnancy with a fetus affected with propionic acidaemia. Although the levels increased linearly between 23 and 39 weeks of gestation, the levels were not significantly elevated above normal until after 30 weeks of gestation. Thus, determination of methylcitric acid in maternal urine is not of value for early prenatal diagnosis of propionic acidaemia.