Abstract

The aim of this prospective study was to compare the endometrial microbiome between pregnant and non-pregnant women after frozen embryo transfer (FET) with euploid embryos. Endometrial biopsies were collected from 30 women during the mid-luteal phase in a natural cycle. FET was performed with euploid embryos up to 3 months after the biopsy. Endometrial microbiota composition was analysed using 16S rRNA (v4-v5 region) next generation sequencing (NGS). The analysis of different clinical outcomes after the biopsy (no pregnancy (n = 14), and ultrasound confirmed pregnancy (n = 16)) revealed differences in the endometrial microbiome composition. In total, 271 distinct bacterial species and 668 bacterial genera were identified. The number of unique species found in non-pregnant women was 62 (22.88%), while in the patients who became pregnant after FET it was 39 (14.39%). Among them, bacteria with high frequency of occurrence such as Bacteroides spp., Cutibacterium granulosum, Isoptericola spp., Acetomicrobium spp., Marivivens spp. and Syntrophomonas spp. were found only in non-pregnant patients, while Bosea spp. was present only in pregnant women. The analysis of bacteria relative abundance revealed that Lactobacillus genus was not significantly different between the studied groups. In contrast, Serratia marcescens, Staphylococcus spp., Glutamicibacter spp. and Delftia spp. were significantly enriched in the non-pregnant group. In conclusion, specific bacteria taxa had higher relative abundance in the endometrium of patients with implantation failure after FET with euploid embryos. We hypothesize that an appropriate treatment for optimization of endometrial microbiome content in women with diagnosed microbiome dysbiosis could be beneficial for improvement of pregnancy rates.

摘要

这项前瞻性研究的目的是比较整倍体胚胎冷冻胚胎移植（FET）后孕妇和非孕妇的子宫内膜微生物组。子宫内膜活检是从自然周期黄体中期的 30 名女性身上采集的。活检后 3 个月内对整倍体胚胎进行 FET。使用 16S rRNA（v4-v5 区域）下一代测序 (NGS) 分析子宫内膜微生物群组成。活检后不同临床结果的分析（未怀孕（n  = 14）和超声确认怀孕（n = 14） = 16))揭示了子宫内膜微生物组组成的差异。总共鉴定出 271 个不同的细菌种类和 668 个细菌属。在非妊娠女性中发现的独特物种数量为 62 种（22.88%），而在 FET 后怀孕的患者中发现的独特物种数量为 39 种（14.39%）。其中，出现频率较高的细菌有拟杆菌属、颗粒角质杆菌、异翅目杆菌属、醋微菌属、马里维氏菌属等。和互养单胞菌属。仅在非怀孕患者中发现，而Bosea spp。仅存在于孕妇中。细菌相对丰度分析表明，乳酸菌研究组之间的属没有显着差异。相反，粘质沙雷氏菌、葡萄球菌属、谷氨酸杆菌属。和代尔夫特亚属。在非妊娠组中显着富集。总之，在整倍体胚胎 FET 植入失败的患者子宫内膜中，特定细菌类群的相对丰度较高。我们假设，对诊断为微生物群失调的女性进行适当的优化子宫内膜微生物群含量的治疗可能有利于提高妊娠率。