A Study Of The Correlation Between Vaginal Flora Diversity And Preterm Birth

Objective Preterm birth is an important cause of infant and child morbidity and mortality worldwide.In this study,we investigated the characteristics of vaginal flora changes in pregnant women with preterm and full-term deliveries by analyzing the vaginal microbiota of these women.Methods Eighty pregnant women who were hospitalized in the Maternal and Child Health Hospital of Anhui Medical University from December 2020 to July 2021 due to preterm labor were selected and followed up the pregnancy outcomes according to the routine obstetric procedures.28 of them were preterm laborers（P group）and 52 were delivered at full term（T group）.42 women with normal pregnancy tests at the same period were selected as the control group and followed up their gestational weeks of delivery（C group）.All of them delivered at full term.Two vaginal secretion specimens were collected from all the subjects,and vaginal microecological testing and high-throughput sequencing technology were used to detect vaginal flora,analyze the vaginal microecology,vaginal flora diversity index,community structure composition and relative abundance of phylum level flora between different groups,and draw the subject operating characteristic curve（ROC）to analyze the predictive value of the relative abundance of different species on preterm delivery.Results（1）The incidence of aerobic vaginitis（AV）and microecological disorders,hydrogen peroxide（H₂O₂）and leukocyte esterase（LE）positivity were higher in the preterm group than in the term group and the control group,and the differences were statistically significant（P<0.05）;the differences in bacterial vaginosis（BV）,vulvovaginal pseudomelanosis（VVC）,mixed vaginitis and salivary acid glycosidase（Sna Se）between the three groups were not statistically significant.（2）In the Alpha diversity analysis,the Shannon index and Simpson index of the preterm group were higher than those of the term group and the control group（P<0.05）.（3）When PCA principal component analysis was used to analyze the difference of Beta diversity of flora,the vaginal flora of preterm and term groups showed a trend of clustering distribution separately with significant differences;some samples of vaginal flora of term and control groups had significant similarity.（4）The analysis at the phylum level showed that the preterm group was mainly composed of the thick-walled phylum（64.42%）,the actinomycetes phylum（28.88%）and the anaphylae phylum（4.20%）;the term group was mainly composed of the thick-walled phylum（88.28%）and the actinomycetes phylum（10.12%）;the control group was mainly composed of the thick-walled phylum（95.16%）and the actinomycetes phylum（3.35%）.（5）At the genus classification level,the main genera in the full-term group were Lactobacillus spp.（85.04%）and Atopobium spp.（9.43%）;in the control group,the main genera were Lactobacillus spp.（94.42%）and Gardnerella spp.（3.19%）;in the preterm group,the main genera were Lactobacillus spp.（46.78%）,Gardnerella（25.78%）,Atopobacter spp.（2.41%）,Prevotella spp.（3.66%）,Streptococcus spp.（3.35%）,and Mycoplasma spp.（3.06%）.（6）The relative abundance of Actinomycetes phylum,Phylum Bacillus phylum,Prevotella spp.,Microbacterium spp.and Mycoplasma spp.were increased in the preterm group compared to the full-term group and the control group（H=0.506,8.135,11.196,11.482,6.423,all P<0.05）,and the relative abundance of Thick-walled Phylum and Lactobacillus spp.were significantly decreased in the preterm group compared to the full-term group and the control group（H=8.745,9.763,both P<0.05）.（7）The relative abundance of Gardnerella spp.combined with Prevotella spp.in the vagina predicted the occurrence of preterm labor with a maximum area under the curve（AUC）of 0.880,with a cut-off value of 0.009,a sensitivity of 80%and a specificity of85%.Conclusion There are differences in the composition of vaginal flora between pregnant women who delivered prematurely and those who delivered at term.Women who delivered prematurely are characterized by increased diversity of vaginal microflora and reduced levels of Lactobacillus,and the relative abundance of Gardnerella spp.combined with Prevotella spp.in the vagina has a predictive value for the occurrence of preterm labor.