J Assist Reprod Genet
. 2024 Apr;41(4):929-938. doi: 10.1007/s10815-024-03066-0. Epub 2024 Feb 22.
Impact of vaginal microecological differences on pregnancy outcomes and endometrial microbiota in frozen embryo transfer cycles
Purpose: This prospective study investigates the correlation between vaginal microecology and pregnancy outcomes and explores their impact onendometrial microbiota composition during frozen embryo transfer (FET) cycles. Additionally, the impact of transvaginal Lactobacillussupplementation on reproductive outcomes in patients with previous failed cycles was assessed.
Methods: A total of 379 patients undergoing FET at a reproductive medicine center were categorized into clinical pregnancy (CP), miscarriage (MISC),and non-pregnant (NP) groups. Vaginal specimens were collected for microecological evaluation prior to embryo transfer. Endometrial microbiotasamples were obtained during embryo transfer for 16S rRNA gene sequencing analysis to assess endometrial microbiota composition. Vaginalmicroecological indicators, including pH, Lactobacillus dominance, and leukocyte esterase activity, were measured. Transvaginal Lactobacillussupplementation was investigated in 60 patients with previous failed cycles.
Results: Vaginal microecology significantly correlated with pregnancy outcomes, with normal microecology associated with a higher clinicalpregnancy rate. Vaginal pH and leukocyte esterase activity were significantly associated with clinical pregnancy. Furthermore, vaginalmicroecological differences significantly impacted endometrial microbiota composition. However, no significant differences were observed inendometrial microbiota composition among the CP, MISC, and NP groups. Notably, transvaginal Lactobacillus supplementation increased the clinicalpregnancy rate without affecting the miscarriage rate.
Conclusion: This study highlights that normal vaginal microecology, characterized by lower pH and leukocyte esterase negativity, is associated with ahigher likelihood of clinical pregnancy following FET. Importantly, vaginal microecological differences influence endometrial microbiotacomposition. Moreover, transvaginal Lactobacillus supplementation appears promising in improving clinical pregnancy rates in patients withprevious failed cycles. These findings contribute to a better understanding of the interplay between vaginal and endometrial microbiota and offerpotential interventions to enhance reproductive success in assisted reproductive technologies.