Endometrial microbiota and reproductive outcome in assisted reproductive technology program

Objective. To evaluate the effect of uterine microbiota on the success of embryo implantation in women undergoing assisted reproductive technology (ART). Patients and methods. The investigation enrolled 80 infertile patients who had undergone IVF programs. Group 1 included 50 patients who had embryos transferred in the stimulation cycle; Group 2 consisted of 30 patients with embryos transferred in the cryo cycle. The women’s mean age was 31.4±1.5 years. The outer walls of an embryo catheter removed from the uterine cavity after embryo transfer were microbiologically tested by culturomics using an expanded set of selective and non-selective culture media. Results. Twenty-seven bacterial species were isolated in Group 1 patients. Pregnancy occurred in 20 (40.0%) women. Lactobacilli, the most abundant bacteria, were detected in 85% of women. Among the opportunistic microorganisms (OMs) in 50.0% of patients, the most common species were Gardnerella vaginalis (G. vaginalis) and Enterococcus faecalis (E. faecalis) in 20.0% of women and Streptococcus anginosus (S. anginosus) in 15.0%. The isolation rate of Lactobacilli was lower in non-pregnant women (60.0%) than in pregnant women (73.3%). The OMs (46.6%), showed a preponderance of G. vaginalis (10.0%) and facultative anaerobic microorganisms, such as S. anginosus (10.0%), Staphylococcus haemolyticus (6.6%), an Actinomyces sp. (6.6%); Haemophilus influenzae (3.3%) is rarely isolated from the genitals. Twenty bacterial species were detected in Group 2 women. Pregnancy occurred in 13 (43.3%) patients. The most abundant bacteria Lactobacilli were isolated in 69.2% of women. The OMs (38.5%) displayed a preponderance of facultative anaerobic microorganisms, such as Escherichia coli and Staphylococcus epidermidis (S. epidermidis) with an equal rate (15.4%). In non-pregnant women (56.7%), the isolation rate of Lactobacilli was 64.7%. Facultative anaerobes, such as S. epidermidis (17.6%) and E. faecalis (11.8%), were most commonly isolated among the OM (41.2%). Bifidobacteria were found in 35.3% of women and Actinomyces neuii were detected in 5.9%. Conclusion. The investigation showed that the best implantation results among 33pregnant women were observed with uterine colonization by only Lactobacilli (42.4%). When the uterus was colonized by Lactobacilli in association with OM, the pregnancy rate was 36.4%, whereas it was 9.1% when it was colonized only by OM. In the absence of endometrial colonization, pregnancy also occurred in only 9.1% of cases.

infertility, assisted reproductive technologies, uterine microbiota, embryo implantation