Metabolic profiling of amniotic fluid by proton nuclear magnetic resonance spectroscopy: correlation with fetal maturation and other clinical variables.

Proton NMR spectroscopy at 600 MHz was performed on 70 specimens of human amniotic fluid, representing pregnancies at different stages of maturation and with different fetomaternal complications. Spectra with good signal-to-noise characteristics were obtained in 3.5 min of acquisition time, directly on untreated fluid, with presaturation to suppress the intense water resonance. Metabolites that generally gave rise to well-resolved resonances included lactate, glucose, creatinine, choline derivatives, citrate, acetate, alanine, glycine, glutamate, succinate, and others. For three of these metabolites--creatinine, glucose, and lactate--the peak intensities correlated well with results of conventional chemical analysis. The NMR spectra of third-trimester specimens were readily distinguishable from those of second-trimester specimens, and several peak intensities correlated with fetal maturation during the third trimester. Significant correlations with maternal preeclampsia and fetal open spina bifida were also observed.