Jun Zhang ^* Li Li ^* Mengjun Zhang ^* Jiaoning Fang ^* Zhimin Xu ^* Yijing Zheng ^* Zhi Lin ^* Mian Pan ^*

• Department of Obstetrics and Gynecology, Fujian Maternity and Child Health Hospital, Fujian, China

Preterm birth (PTB) is a major cause of infant morbidity and mortality. The aim of this study was to investigate the effect of vaginal microbiota and metabolites on the outcome of pregnant women. In this study, a total of 127 pregnant woman provided written informed consent prior to enrollment in accordance with the approved institutional guidelines, but only 45 pregnancies met the experimental requirements, and then blood and cervical vaginal fluid (CVF) samples were collected before delivery (at the 2 th week after cervical cerclage). Pregnant woman with preterm birth (PTB) exhibited high contents of white blood cell, neutrophil, the rate of neutrophil and lymphocyte (NLR) and systemic inflammation response index (SIRI) in the blood. Vaginal microbiome revealed that the proportion of beneficial bacteria (including Lactobacillus,[Ruminococcus] gnavus group, Megamonas, et al.) significantly decreased in the PTB group, and the proportion of harmful bacteria (including Desulfovibrionaceae, Helicobacter, Gardnerella, et al) significantly increased, which is strongly related to the biochemical parameters of blood (white blood cells, neutrophil, NLR, and SIRI). In addition, vaginal metabolomics-based liquid chromatography-Orbitrap-mass spectrometry/mass spectrometry (LC-Orbitrap-MS/MS) found that the alteration in vaginal metabolites in the pregnant woman with PTB, which is involved in starch and sucrose metabolism, arginine and praline metabolism, galactose metabolism, purine metabolism, arginine metabolism, tryptophan metabolism and N-Glycan biosynthesis, cysteine and methionine metabolism, taurine and hypotaurine metabolism, amino acid metabolism, propanoate metabolism, valine, leucine and isoleucine biosynthesis, glycine, serine and threonine metabolism, and steroid hormone biosynthesis. These results elaborated that distinct vaginal microbiome and metabolome profiles in women with preterm delivery following cervical cerclage, which provides valuable information for establishing the prediction models for PTB.