Quantitative metabolic profiles of 2nd and 3rd trimester human amniotic fluid using super(1)H HR-MAS spectroscopy

Object: To establish and compare normative metabolite concentrations in 2nd and 3rd trimester human amniotic fluid samples in an effort to reveal metabolic biomarkers of fetal health and development. Materials and methods: Twenty-one metabolite concentrations were compared between 2nd (15-27 weeks gestation, N = 23) and 3rd (29-39 weeks gestation, N = 27) trimester amniotic fluid samples using super(1)H high resolution magic angle spinning (HR-MAS) spectroscopy. Data were acquired using the electronic reference to access in vivo concentrations method and quantified using a modified semi-parametric quantum estimation algorithm modified for high-resolution ex vivo data. Results: Sixteen of 21 metabolite concentrations differed significantly between 2nd and 3rd trimester groups. Betaine (0.00846 plus or minus 0.00206 mmol/kg vs. 0.0133 plus or minus 0.0058mmol/kg, P < 0.002) and creatinine (0.0124 plus or minus 0.0058mmol/kg vs. 0.247 plus or minus 0.011mmol/kg, P < 0.001) concentrations increased significantly, while glucose (5.96 plus or minus 1.66mmol/kg vs. 2.41 plus or minus 1.69 mmol/kg, P < 0.001), citrate (0.740 plus or minus 0.217 mmol/kg vs. 0.399 plus or minus 0.137mmol/kg, P < 0.001), pyruvate (0.0659 plus or minus 0.0103mmol/kg vs. 0.0299 plus or minus 0.286mmol/kg, P < 0.001), and numerous amino acid (e.g. alanine, glutamate, isoleucine, leucine, lysine, and valine) concentrations decreased significantly with advancing gestation. A stepwise multiple linear regression model applied to 50 samples showed that gestational age can be accurately predicted using combinations of alanine, glucose and creatinine concentrations. Conclusion: These results provide key normative data for 2nd and 3rd trimester amniotic fluid metabolite concentrations and provide the foundation for future development of magnetic resonance spectroscopy (MRS) biomarkers to evaluate fetal health and development.