Interpretations
Disruption of balance of vaginal microbiota causes invades of several facultative or strict anaerobes, including Gardneralla vaginalis, Mycoplasma hominis, Prevotella spp., Fusobacterium spp ., Ureoplasma spp., and Porphyromonas spp. and replacement ofLactobacilli 26–28. Aligning with the aforementioned results, we identified a significantly higher abundance of Bacteroidetes in COVID-19 group. In particular, Prevotella timonensis was only identified in women with COVID-19 (0.04%). Likewise, Dialister propionicifaciens appeared in the COVID-19 group (0.02%). The SARS-CoV-2 infection triggers the production of prostaglandins and pro-inflammatory mediators to confer ischemia resulting in widespread tissues 29,30. Notably, we determined an increase of anaerobic species such as Gardnerella vaginalis , Anaerococcus tetradius , Fusobacterium nucleatum , Prevotella timonensis abundance in women with severe disease. Based on these results, we postulated that ischemia in genito-urinary compartments could be a predisposing factor for overgrowth of anaerobes in vaginal microbiota.
Pregnant women are more susceptible to SARS-CoV-2 infection due to physiological, mechanical, and immunological changes during pregnancy2,31. Data supported that pregnancy is a risk factor for severe disease related to COVID-19 4,32. Recently, in a large population-based cohort study, fetal death and preterm birth occurred more frequently in women with SARS-CoV-2 infection than non-infected women (adjusted odds ratio (aOR), 2.21; 95% confidence interval (CI), 1.58 – 3.11; P< 0.001 and OR, 2.17; 95% CI, 1.96 – 2.4; P<0.001, respectively) 1. In the study, the prevalence of preterm birth (15.3%) was high, especially in the severe COVID-19 (2 out of 3 preterm birth), as compared to the prevalence reported before COVID-19 (9.6%) 33. Even with the small sample size of our study, the rate of preterm birth increased in women with severe COVID-19 disease than those with asymptomatic or mild disease, aligning with a recent meta-analysis34. The abundance of Ureaplasma andMycoplasma species increased the risk of preterm delivery through chorioamnionitis, salpingitis, bacterial vaginosis, and postpartum endometritis 20,35. We found that Mycoplasma hominis (8% vs. 0%; P=0.01) and Ureaplasma spp. (2.09% vs. 0.04%, p=0.001) showed significantly higher abundance in moderate or severe cases compared to those of the healthy controls. Of note, the abundance of Ureaplasma spp. was significantly higher in women with moderate or severe disease than those of asymptomatic or mild disease (p=0.005). We claim in light of these findings and previous evidence from microbiota studies that the subsequent preterm birth in women with severe disease could be a consequence of impaired vaginal composition.