| Background and purpose:Preterm birth is one of the common perinatal complications and the main cause of perinatal death.The incidence of preterm birth is high,but the pathogenesis of preterm birth has not been clarified,and the symptoms of preterm birth are lack of specificity,and there are no clear screening and prevention methods.Studies have confirmed that preterm birth is associated with oral flora imbalance caused by periodontitis during pregnancy,and that oral-fecal transmission patterns play an important role in shaping health and disease during pregnancy.The imbalance of intestinal flora during pregnancy is closely related to adverse pregnancy outcomes such as gestational diabetes mellitus and preeclampsia,but there are few studies on its correlation with threatened preterm birth.In this study,starting from the intestinal flora of pregnant women,16 S r RNA high-throughput sequencing technology was used to analyze the change characteristics of the intestinal flora of pregnant women in the control group and the threatened preterm labor group.Combined with the final pregnancy outcome,different bacteria were screened out,and the relationship between different bacteria and host clinical parameters was explored,providing new insights for the screening and prevention of patients with threatened preterm labor clinically.Contents and methods:1.Specimen Collection: A total of 41 healthy pregnant women without preterm birth and pregnant women with preterm birth without preterm birth were selected from September 2020 to June 2021 in the Obstetrics clinic and inpatient department of the First Affiliated Hospital of Nanchang University.Fecal samples of similar gestational age were provided to track the pregnancy outcome.Clinical information such as age,BMI,CRP,gestational age at delivery,neonatal weight and Apgar score was collected.According to the gestational age at the time of delivery before and after 34 weeks,they were divided into three subgroups: early preterm delivery group(≥ 28 weeks but < 34 weeks),late preterm delivery group(≥ 34 weeks but < 37 weeks)and full-term delivery group(≥ 37 weeks but < 42 weeks).2.Specimen treatment: Bacterial DNA in feces was extracted,16 S r DNA V4 region gene amplification was performed,amplified products were sequenced using Illumina-Miseq platform,sequencing data processing and species annotation were performed.3.Data analysis: alpha diversity analysis,β diversity analysis and LFEse analysis were performed on the sequencing results,and displacement multivariate analysis of variance and Person correlation analysis were used to calculate the degree of correlation between intestinal flora changes and clinical parameters in the threatened preterm birth group and the control group.Results:1.Diversity analysis: The Shannon index and PD whole tree index of intestinal flora alpha diversity in threatened preterm delivery group were significantly higher than those in control group(P < 0.05),but there was no significant difference in alpha diversity in preterm delivery subgroup.Principal coordinate analysis of beta diversity analysis showed that there was significant difference in the overall structure of intestinal flora between the threatened preterm delivery group and the control group(P = 0.004),and the preterm delivery subgroup showed a tendency to gradually move away from the control group with the decrease of gestational week(P = 0.019).2.Comparison of phylum/genus levels: Phylum level analysis showed that Firmicutes,Proteobacteria,Actinobacteria,Bacteroidetes,Verrucomicrobia and Fusobacteria were relatively abundant in the intestinal flora of the threatened preterm delivery group,the control group and each preterm delivery subgroup.At the genus level,LEFse analysis showed that the relative abundance of Lactobacillus,Streptococcus,Neisseria,Haemophilus,Lautropia,porphyromonas,Clostridium,Prevotella,Rothia,Oscillospira,Granulicatella,Actinomyces and Bilophila in the threatened preterm delivery group had a higher relative abundance,while the relative abundance of Coprococcus and Gemmiger the control group was higher.Streptococcus,porphyromonas and Clostridium in the threatened preterm delivery group were similar to common oral pathogenic bacteria in the Human Oral Microbiome Database(HOMD).3.Correlation analysis of intestinal flora imbalance and host parameters: The changes of intestinal microflora between the threatened preterm delivery group and the control group were significantly correlated with gestational age,neonatal weight and Apgar score at delivery(P<0.05).In the preterm birth subgroup,maternal age,BMI at delivery,gestational age,CRP,neonatal weight and Apgar score were significantly correlated with changes in intestinal microbial community(P<0.05).The relative abundance of Hom D-anastomosed oral-intestinal bacteria enriched in the gut was negatively correlated with gestational age at delivery,neonatal weight,and Apgar score.Conclusion:1.The richness and evenness of intestinal flora in pregnant women with threatened preterm delivery were significantly increased,and the overall structure of bacterial flora was significantly different from that in the control group,and the diversity of bacterial flora was unbalanced.2.In the pregnant women with preterm birth,a high proportion of bacteria enriched in the gut are consistent with oral bacteria,which may result in oral-intestinal bacterial translocation.3.The imbalance of intestinal flora may be related to the clinical parameters reflecting the intrauterine conditions of the mother and fetus.The appearance of different bacteria and the change of bacterial diversity may provide the possibility for the early identification and treatment of threatened preterm labor. |
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