Melatonin is a hormone produced by the pineal gland and it has antioxidant properties. This study aimed to evaluate the effects of melatonin on assisted reproductive technologies through a systematic review and a meta-analysis. Search strategies were used in PubMed and in other databases covering the last 15 years. After screening for eligibility, 17 articles were selected for the systematic review. For the meta-analysis statistics, two groups were formed, the treatment group (with melatonin) and the control group (without melatonin) for various assisted reproduction outcomes. The main results were that no statistical differences were found concerning the clinical pregnancy outcome (p = 0.64), but there was a statistical difference with respect to Mature Oocytes (MII) (p = 0.001), antral follicle count (p = 0.0002), and the fertilization rate (p ≤ 0.0001). Melatonin had beneficial effects such as the improvement in the fertilization rate, although the authors did not obtain significance in the clinical pregnancy rate.

Background: The vaginal microbiome is an important factor influencing clinical outcomes in women undergoing assisted reproductive techniques. Objective: Our review aimed to confirm that women with a favorable vaginal microbiome have better reproductive outcomes than women who have an unfavorable vaginal microbiome. Methods: This systematic review and meta-analysis included articles published in the last 10 years, identified through keyword searches in PubMed and MEDLINE using the MeSH terms “vaginal microbiome,” “reproduction,” and “human reproduction.” The search yielded 1735 records. Participants were categorized into women with a favorable microbiome and those with an unfavorable microbiome. To refine the taxonomic resolution at the species level, we additionally performed a bioinformatic analysis of a cohort of 56 women using multivariable association with linear models (MaAsLin2). Results: Women with a favorable microbiome had higher pregnancy rates compared to those with a less favorable microbiome (p = 0.0001, I2 = 0%, RR: 1.59). Live birth rates were also significantly higher in the favorable microbiome group than in the unfavorable microbiome group (p = 0.004, I2 = 0%, RR:1.41), with no evidence of heterogeneity. Women with an unfavorable microbiome had more miscarriages than women with a favorable microbiome (p = 0.04, I2 = 0%, RR: 0.65). Bioinformatic analysis showed that a high relative abundance of Lactobacillus crispatus increased the likelihood of pregnancy approximately sixfold. Conclusions: The favorable microbiome group, particularly participants with a high relative abundance of Lactobacillus crispatus, demonstrated better reproductive outcomes, with a higher clinical pregnancy rate, a higher live birth rate, and a lower rate of pregnancy loss, although there was a low-quality bias.

Most women suffering from tubal factor infertility do not have a history of pelvic inflammatory disease, but rather have asymptomatic upper genital tract infection. Investigating the impacts of such infections, even in the absence of clinically confirmed pelvic inflammatory disease, is critical to understanding the tubal factor of infertility. The aim of this study was to investigate whether the presence of endocervical bacteria is associated with tubal factors in women screened for infertility. This retrospective cross-sectional study involved 245 women undergoing hysterosalpingography (HSG), screened for endocervical colonization by Chlamydia trachomatis, Neisseria gonorrhea, Ureaplasma urealyticum and Mycoplasma hominis, as part of a routine female infertility investigation between 2016 and 2017. endocervical bacterial colonization by Chlamydia trachomatis, Ureaplasma urealiticum, Mycoplasma hominis and other bacteria corresponded to 3.7%, 9.0%; 5.7% and 9.8%, respectively. There was no colonization by Neisseria gonorrhea. The prevalence of tubal factor was significantly higher in patients with positive endocervical bacteria colonization, regardless of bacterial species. When evaluating bacteria species individually, the women who were positive for endocervical Mycoplasma hominis had significantly higher rates of tubal factor. Associations between endocervical bacterial colonization and tubal factor infertility were confirmed by multiple regression analysis adjusted for age and duration of infertility. Besides the higher prevalence of Mycoplasma and Ureaplasma infectious agents, the findings of this study suggest the possible association of endocervical bacterial colonization - not only Chlamydia trachomatis and Neisseria gonorrhea, but also Mycoplasma species with tubal performance.

Chronic endometritis (CE) is defined as a localized inflammation signaled by the infiltration of bacteria in the endometrial stroma. It has adverse implications in human reproduction, including recurrent implantation failure (RIF) and recurrent miscarriage¹ 1 Kitaya K, Takeuchi T, Mizuta S, Matsubayashi H, Ishikawa T. Endometritis: new time, new concepts. Fertil Steril. 2018;110(3):344-50. https://doi.org/10.1016/j.fertnstert.2018.04.012 https://doi.org/10.1016/j.fertnstert.201... –³ 3 Puente E, Alonso L, Laganà AS, Ghezzi F, Casarin J, Carugno J. Chronic endometritis: old problem, novel insights and future challenges. Int J Fertil Steril. 2020;13(4):250-6. https://doi.org/10.22074/ijfs.2020.5779 https://doi.org/10.22074/ijfs.2020.5779... .