Polat IH, Marin S, Ríos J, et al. - Via performing exploratory and confirmatory analyses, researchers examined the presence of vaginal metabolome expression of microbial invasion of the amniotic cavity in women diagnosed as having preterm labor using high-performance liquid chromatography. Vaginal amino acid concentrations were analyzed in 140 women with singleton pregnancies and a diagnosis of preterm labor at < 34 weeks’ gestation employing high-performance liquid chromatography. They obtained vaginal samples shortly after the amniocentesis performed at admission to rule out microbial invasion of the amniotic cavity. Data were normalized for the median of all the amino acid concentrations evaluated. In the exploratory cohort (2014–2015), microbial invasion of the amniotic cavity was noted in 17 of 76 women (22.3%) vs 14 of 72 (19.4%) in the confirmatory cohort (2016–2017). In the exploratory cohort, amino acid concentrations of vaginal taurine, lysine, and cysteine were significantly higher and concentrations of vaginal glutamate, aspartate, and the aspartate to asparagine ratio were significantly lower. The confirmatory cohort confirmed these significant differences. These findings may aid in developing noninvasive diagnostic tools of microbial invasion of the amniotic cavity with the aim of selecting women who would most likely benefit from an amniocentesis for this indication.