Microbial invasion of the amniotic cavity (MIAC) is only identified by amniocentesis, an invasive procedure that limits its clinical translation. Here, we aimed to evaluate whether the vaginal metabolome discriminates the presence/absence of MiAc in women with preterm labor (ptL) and intact membranes. We conducted a case-control study in women with symptoms of PTL below 34 weeks who underwent amniocentesis to discard MIAC. MIAC was defined as amniotic fluid positive for microorganisms identified by specific culture media. The cohort included 16 women with MIAC and 16 control (no MIAC). Both groups were matched for age and gestational age at admission. Vaginal fluid samples were collected shortly after amniocentesis. Metabolic profiles were analyzed by nuclear magnetic resonance (nMR) spectroscopy and compared using multivariate and univariate statistical analyses to identify significant differences between the two groups. The vaginal metabolomics profile of MiAc showed higher concentrations of hypoxanthine, proline, choline and acetylcholine and decreased concentrations of phenylalanine, glutamine, isoleucine, leucine and glycerophosphocholine. in conclusion, metabolic changes in the NMR-based vaginal metabolic profile are able to discriminate the presence/absence of MiAc in women with ptL and intact membranes. these metabolic changes might be indicative of enhanced glycolysis triggered by hypoxia conditions as a consequence of bacterial infection, thus explaining the utilization of alternative energy sources in an attempt to replenish glucose. Maternal and fetal medicine is moving toward individualized patient-care aiming to identify the most appropriate clinical management for each woman. In women with preterm labor (PTL), early spontaneous preterm deliveries (PTD) are more likely related to microbial invasion of the amniotic cavity (MIAC) and intra-amniotic inflammation (IAI) 1. Diagnosis of MIAC help clinicians to identify women with high-risk of delivering in the following days 2. This information may be used to efficiently plan antenatal management 3 by transfer to facilities with Neonatal Intensive Care Units (NICU), administration of antenatal steroids 4 , magnesium sulfate 5 and, probably, with specific antibiotics 6 according to the microorganism isolated. Furthermore, additional information about MIAC may not only render antenatal strategies, such as tocolysis, questionable, but may also help neonatologists improve neonatal management. Nowadays, amniocentesis is the only procedure to identify MIAC since it can occur without a clinical suspicion. Despite the very low rate of complications associated with amniocentesis 7 , the invasive nature of this