目的:描述孕前与孕晚期女性口腔菌群的特征及差异。方法:本研究为回顾性队列研究。研究对象为2016年9月至2019年12月在上海市嘉定区妇幼保健院参与复旦孕前队列研究并随访至孕晚期的55例女性。采用16S rRNA测序技术检测55例女性、共110份（孕前与孕晚期各55份）唾液样本菌群，并进行菌群特点的相关因素分析。α多样性指数在孕前与孕晚期组间的差异比较采用配对n t检验或Wilcoxon配对符号秩和检验，不同特征组间比较使用n t检验、方差分析、Kruskal-Wallis检验或Mann-Whitney n U检验；以置换多元方差分析比较β多样性差异；采用LEfSe 1.0软件以线性判别分析效应值法分析标志性口腔微生物。n 结果:（1）与孕前相比，孕晚期口腔菌群Ace指数降低[730.64（632.40~911.00）与661.14（578.15~752.85），n T=1 077.000，n P=0.010]，β多样性差异亦有统计学意义（n F=12.539，n R2=0.104，n P=0.001）；孕晚期口腔单糖菌门G3菌属（n Saccharibacteria_TM7_G3）、普雷沃菌_7属（n Prevotella_7）、n Absconditabacteria_SR1_G1菌属、卟啉单胞菌属（n Porphyromonas）、瘤胃菌UCG014属（n Ruminococcaceae_UCG_014）、普雷沃菌属（n Prevotella）、消化链球菌属（n Peptostreptococcus）、普雷沃菌_2属（n Prevotella_2）、拟普雷沃菌属（n Alloprevotella）、微单胞菌属（n Parvimonas）、n Solobacterium菌属、缠结真杆菌属（n Eubacterium_nodatum_group）丰度更高（n P值均<0.05）。（2）单因素分析结果显示，孕晚期时，收入水平较低者、饭后或甜食后及时漱口者Shannon指数较低[分别为5.44（5.08~5.77）与5.75（5.44~6.12），5.36（4.91~5.48）与5.72（5.44~6.05），n U值分别为219.000和374.000，n P值均<0.05]。n 结论:孕前与孕晚期女性口腔菌群结构存在差异，孕晚期口腔致病菌及机会致病菌显著增加。“,”Objective:To summarize and compare the characteristics of oral microbiota in women during the preconception period and the third trimester.Methods:This retrospective cohort study involved 55 women who were recruited in the Preconceptional Offspring Trajectory Study (PLOTS) conducted by Fudan University and followed up to the third trimester in the Maternal and Child Health Care Hospital of Jiading District of Shanghai from September 2016 to December 2019. A total of 110 unstimulated saliva samples were collected in the preconception period (n n=55) and the third trimester (n n=55). Features of oral microbiota in the samples were analyzed by 16S rRNA gene-based sequencing. Moreover, the related factors were also analyzed. Paired n t test or Wilcoxon matched-pairs signed-ranks test were used to analyze the differences in α-diversity during preconception and the third trimester; n t test, analysis of variance (ANOVA), Kruskal-Wallis test and Mann-Whitney n U test for comparison between groups with different characteristics and permutational multivariate analysis of variance (PerMANOVA) for β-diversity were used; Linear discriminant analysis (LDA) effect size (LEfSe 1.0) was used to identify the iconic oral flora.n Results:(1) The Ace index of oral microbiota was significantly lower in the third trimester than that in the preconception period [661.14(578.15-752.85) vs 730.64 (632.40-911.00), n T=1 077.00, n P=0.010]. There was also a significance difference in β-diversity ( n F=12.539, n R2=0.104, n P=0.001). Some species such as n Saccharibacteria_TM7_G3, n Prevotella_7, n Absconditabacteria_SR1_G1, n Porphyromonas, Ruminococcaceae_UCG_014, n Prevotella, n Peptostreptococcus, n Prevotella_2, n Alloprevotella, n Parvimonas, n Solobacterium and n Eubacterium_nodatum_group in saliva were statistically more abundant in the third trimester than those in the preconception period (all n P<0.05). (2) The third-trimester Shannon index was lower among those with lower income [5.44 (5.08-5.77) vs 5.75 (5.44-6.12),n U=219.00, n P=0.029] and those with gargle habit after meal or dessert [5.36 (4.91-5.48) vs 5.72 (5.44-6.05), n U=374.00, n P=0.046].n Conclusions:The features of oral microbiota vary in women during the preconception period and the third trimester. There is a significant increase in the abundance of oral pathogenic and opportunistic bacteria in the third trimester.