Comparison of metabolite levels in second and third trimester human amniotic fluid samples using proton magnetic resonance spectroscopy

Objective: The objective of this study was to evaluate proton magnetic resonance as an analytical tool in the investigation of metabolites in third trimester human amniotic fluid by comparison with literature values, including second trimester data. Methods: Normal human amniotic fluid from the third trimester has been examined using proton magnetic resonance spectroscopy at moderate field strength (300 MHz). Several small molecules were identified and quantitated using an external, added standard. The mean values of the concentrations were compared with second trimester data obtained using nuclear magnetic resonance as well as with clinical chemistry literature values. Results: Third trimester concentrations were significantly lower for alanine, citrate, and glucose compared with second trimester. Acetate, creatine/creatinine, and lactate levels were not different. Histidine, tyrosine, and valine present in second trimester fluids at detectable amounts were very low and often not distinguishable from spectral baseline noise, Lactate was proposed as a possible internal standard for quantitation. Conclusions: Proton magnetic resonance was shown to be an analytical tool of human amniotic fluid. The described technique did not allow for proper resolution in order to differentiate creatine/creatinine, The ratios of the mean concentrations between trimester samples using maleate and lactate as intensity references were in close agreement.