Effects Of Uterine Microbiome On Pregnancy Outcome In Infertile Women

Objective:The purpose of this study was to compare the distribution of uterine and cervical microflora in infertile women undergoing in vitro fertilization and embryo transfer（IVF-ET）,to analyze the relationship between uterine cavity and cervical microflora and vaginal microecology,to analyze the effect of uterine cavity and cervical microflora on pregnancy outcome,and to discuss the factors affecting the distribution of uterine microflora.Methods:A total of 139 IVF-ET cycles were included in this study.Endometrial receptivity was evaluated by fore-dimensional ultrasound in the morning of embryo transfer day.Vaginal microecological examination was done before embryo transfer.After embryo transfer,endometrial fluid and cervical mucus were collected from the tip and outer sheath of the transplanted catheter for microbial culture.Matrix-assisted laser desorption/ionization time of flight mass spectrometry was used to identify intrauterine and cervical microbes respectively.According to the results of microbial identification by mass spectrometry and whether the dominant bacteria were Lactobacillus,they were divided into 3 groups.Results:1.Identification of uterine microbiome and its grouping:The positive rate of uterine microbiota identified by MALDI-TOF MS was 74.10%.The top four bacteria in uterine cavity and cervix were Lactobacillus（51.09%&46.40%）,Streptococcus（14.13%&17.60%）,Staphylococcus（13.04%&14.40%）and Corynebacterium（6.52%&6.40%）.In uterine cavity,there were 47,25 and 67 cycles in the Lactobacillus dominant group,the non-Lactobacillus dominant group and the negative group respectively.In cervix,each group had 58,35 and 46 cycles respectively.2.Uterine microbiome and vaginal microecology:In uterine cavity,the proportion of normal vaginal flora density in the non-Lactobacillus dominant group was significantly lower than that in the Lactobacillus dominant group and the negative group（P<0.0167）.Compared with Lactobacillus dominant group,the proportion of vaginal dominant Lactobacillus and Nugent score of 0～3 was significantly decreased in the non-Lactobacillus dominant group of uterine cavity,while the proportion of Nugent score of 4～6 and the vaginal microecological disorders was significantly increased（P<0.0167）.Compared with both Lactobacillus dominant group and the negative group,the proportion of normal vaginal flora density,vaginal dominant Lactobacillus and Nugent score of 0～3 was significantly decreased in the non-Lactobacillus dominant group of cervix,while the proportion of Nugent score of 4～6 was significantly increased（P<0.0167）.3.Uterine microbiome and pregnancy outcome:In both uterine cavity and cervix,the positive rate of HCG rate in the non-Lactobacillus dominant group was significantly lower than that in the Lactobacillus dominant group（P<0.0167）.In uterine cavity,the implantation rate,clinical pregnancy rate and live birth rate in the non-Lactobacillus dominant group was lower than that in the Lactobacillus dominant group（P<0.0167）.For those who had Lactobacillus in uterine cavity,clinical pregnancy rate and live birth rate were significantly higher than those without Lactobacillus（P<0.05）.Gardner bacteria were detected in uterine cavity,and the live birth rate was significantly lower than that of those non detected（P<0.05）.When the vaginal microecology was not dysregulated,the live birth rate of the Lactobacillus dominant group in uterine cavity was significantly higher than that of the non-Lactobacillus dominant group and the negative group（P<0.0167）.Logistic analysis showed that vaginal microecology and the distribution of uterine cavity microbial community were related to the clinical pregnancy rate and live birth rate in each group of uterine cavity,and their effects on clinical pregnancy rate and live birth rate were interactive（P<0.05）.Vaginal microecology was correlated with the live birth rate of each group of cervix（P<0.05）.4.The factors influencing the distribution of uterine microflora:The thickness of endometrium on the day of transplantation in the non-Lactobacillus dominant group was thicker than that in the negative group（P<0.05）.The E₂ level on transplantation day in the non-Lactobacillus dominant group was significantly higher than that in the Lactobacillus dominant group and the negative groups（P<0.0167）.Compared with the Lactobacillus dominant group and negative group,there was a significant decrease in the proportion of FET cycles in the non-Lactobacillus dominant group and a significant increase in the proportion of ET cycles（P<0.0167）.Compared with the Lactobacillus dominant group,the percentage of vaginal microecological dysbiosis cycles was significantly increased in the non-Lactobacillus dominant group（P<0.0167）.Logistic regression analysis shows that,taking the non-Lactobacillus dominant group as reference group,normal vaginal microecological in the Lactobacillus dominant group was 3.614times the probability of vaginal microecological disorders[OR=3.614,95%CI=（1.442,9.056）,P=0.006].The risk of E₂ reduction on transplantation day of the Lactobacillus dominant group was 0.999 times of that of the non-Lactobacillus dominant group[OR=0.999,95%CI=（0.999,1.000）,P=0.008].The probability of E₂ increase on transplantation day of the negative group was 0.999 times of that of the non-Lactobacillus dominant group[OR=0.999,95%CI=（0.998,1.000）,P=0.002].Conclusions:The presence of the non-Lactobacillus dominant genus in uterine cavity is associated with adverse pregnancy outcome.IVF-ET live birth rate increased when the intrauterine microorganism was dominated by Lactobacillus and the vaginal microecology was not dysregulated.Vaginal microecological disorders or excessive E₂ on transplant days may increase the risk of uterine non-Lactobacillus detection.