Endometrial microbiota in infertile women with and without chronic endometritis as diagnosed using a quantitative and reference range-based method

Chronic inflammation occurs in the uterus of about 9% of infertile women in Hong Kong. This is related to higher levels of certain bacteria identified in our study.

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Volume 112, Issue 4, Pages 707–717.e1


Yingyu Liu, Ph.D., Elaine Yee-Ling Ko, B.Sc., Karen Ka-Wing Wong, M.Phil., Xiaoyan Chen, Ph.D., Wing-Ching Cheung, Ph.D., Tracy Sze-Man Law, MB.ChB., Jacqueline Pui-Wah Chung, MB.ChB., Stephen Kwok-Wing Tsui, Ph.D., Tin-Chiu Li, M.D., Ph.D., Stephen Siu-Chung Chim, Ph.D.



To systematically compare the endometrial microbiota in infertile women with and without chronic endometritis (CE), as diagnosed by a quantitative and reference range-based method.


Case-control observational study.


University-affiliated hospital.


One hundred and thirty infertile women.


Endometrial biopsy and fluid (uterine lavage, UL) collected precisely 7 days after LH surge, with plasma cell density (PCD) determined based on Syndecan-1 (CD138)-positive cells in the entire biopsy section and culture-independent massively parallel sequencing of the 16S ribosomal RNA gene performed on both the CE and non-CE endometrial fluid samples.

Main Outcome Measure(s)

Relative abundance of bacterial taxa.


Chronic endometriosis was diagnosed if the PCD was above the 95th percentile (>5.15 cells per 10 mm2) of the reference range in fertile control subjects. With this stringent diagnostic criterion, 12 women (9%) were diagnosed with CE. Sequencing was successfully performed on all endometrial samples obtained by UL) (CE, n = 12; non-CE, n = 118). The median relative abundance of Lactobacillus was 1.89% and 80.7% in the CE and non-CE microbiotas, respectively. Lactobacillus crispatus was less abundant in the CE microbiota (fold-change, range: 2.10–2.30). Eighteen non-Lactobacillus taxa including DialisterBifidobacteriumPrevotellaGardnerella, and Anaerococcus were more abundant in the CE microbiota (fold-change, 2.10–18.9). Of these, Anaerococcusand Gardnerella were negatively correlated in relative abundance with Lactobacillus (SparCC correlation magnitude, range: 0.142–0.177).


Chronic endometriosis was associated with a statistically significantly higher abundance of 18 bacterial taxa in the endometrial cavity.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders.