Table 3: Methodology, findings, and main conclusions derived from metabolomics studies on amniotic fluid.

Population studyGestational age at examinationMetabolomic analysisMain resultsSignificance/take-home messagesReferenceAuthor, year

14 pregnancies with spina bifida fetuses versus 18 controls Second and third trimester (at amniocentesis and cesarean section)1H NMRAlterations in the concentrations of succinic acid, glutamine, creatine, creatinineMetabolomics can point out derangements in aminoacids metabolism in fetuses with spina bifida and help to diagnose it[40]Groenen et al., 2004

Healthy pregnanciesSecond trimester (16-17 ws)RP-LC, MS
1H NMR
60 metabolitesExtended metabolite database for detecting biomarkers of pregnancy disorders[39]Graça et al., 2008

51 healthy pregnancies versus 12 fetal malformations second trimester (15–24 ws)NMRGlucose, free lactate levels, succinate, gluconeogenic aminoacids, glutamine, glycine, urea, glutamine/glutamate ratiosMetabolomics may help detecting malformed fetuses (due to the changes in glycolysis and gluconeogenesis, and their kidney underdevelopment)[38]Graça et al., 2009

82 normal pregnancies
27 fetal malformation
22 metabolites, inclusion of new metabolites: ascorbate, α oxoisovalerate, creatinine, isoleucine, serine, threonineMetabolomics might be able to identify biomarkers of prenatal disorders
27 prediagnostic GDMSecond trimester1H NMRGlucose, amino acids, organic acids, creatinine, glycerophosphocholine (GPC) [37]Graça et al., 2010
12 preterm deliveryAllantoine, alanine, citrate, myoinositol
34 PROM
10 chromosomopathies
Minor metabolic profile changes
no relevant changes

2 studies including
16 + 40 PTL → at term
19 + 33 PTL without IAI
20 + 40 PTL with IAI
Second and third trimester (22–35 ws)LC/MS
GC/MS
Carbohydrates, amino acids, presence of xenobiotic compounds (salicylamide, bacterial products) Classification of patients at risk for PTL with 88.5% accuracy Metabolic profiling of amniotic fluid can be used to assess the risk of preterm delivery with or without IAI[41]Romero et al., 2010

36 controls
29 fetal malformations
37 prediagnostic GDM
34 preterm delivery
Second trimesterUPLC-MS
NMR
New results: changes in pyroglutamate, hippurate
No relevant changes
Potential of the tandem use of MS and NMR for metabolomics studies of urine and amniotic fluid in pregnant women[30]Graça et al., 2012

1H NMR: proton nuclear magnetic resonance spectroscopy; RP-LC: reverse phase liquid chromatography; MS: mass spectrometry; GDM: gestational diabetes mellitus; PROM: premature rupture of membranes; PTL: preterm labor; IAI: intraamniotic infection/inflammation; LC/MS: liquid chromatography/mass spectrometry; GC/MS: gas chromatography/mass spectrometry; UPLC-MS: ultra performance liquid chromatography-mass spectrometry; NMR: nuclear magnetic resonance spectroscopy.