A Potential Role for the Uterine Microbiome in Missed Abortions

Abstract

Purpose: Uterine microbial balance is an important factor affecting embryo implantation and pregnancy. Microbial balance can lead to diseases such as chronic endometritis, which can cause embryo implantation failure or miscarriage. This study aims to explore the composition of uterine microbiota and the potential role of microbiota in missed abortion. Methods: We enrolled 17 patients diagnosed with missed abortion which chromosomal abnormalities were excluded by chromosomal testing and 12 healthy pregnant patients at 6–8 weeks gestation. Endometrial fluid samples were collected and amplified after DNA was extracted. Microbiota components of the uterine environment were identified using the 16S rRNA sequencing. We used the microbiota diversity data to reflect bacterial species richness and evenness within populations, while beta-diversity were performed to measure the shared diversity between populations of bacteria. Results: Microbiomes were found in low abundance both in patients with missed abortion and those with normal pregnancies. There was a greater diversity of intrauterine microflora in patients who missed abortions compared to those who missed deliveries (p < 0.05). In terms of alpha diversity, no significant difference was observed between the two groups (p > 0.05), but there was a significant difference in terms of beta diversity. Moment array analysis by principal co-ordinates analysis (PCoA) did not show significant differences. The bacteria, Proteobacteria and Firmicutes, were significantly elevated in the patients with missed abortion than those in the normal pregnancy group. Conclusions: This study revealed the specificity of uterine microorganisms in patients with embryo arrest, and found that Proteobacteria and Firmicutes play an important role in this process. They may serve as biomarkers of microorganismal diversity in the uterine cavity in embryonic loss of fetus.