Wassenaar, T. M., & Panigrahi, P. (2014). Is a foetus developing in a sterile environment? Letters in Applied Microbiology, 59(6), 572-579. https://doi.org/10.1111/lam.12334
Wassenaar TM, Panigrahi P. Is a foetus developing in a sterile environment? Lett Appl Microbiol. 2014;59(6):572-579. doi:10.1111/lam.12334
Wassenaar, T. M., and P. Panigrahi. "Is a foetus developing in a sterile environment?" Letters in Applied Microbiology, vol. 59, no. 6, 2014, pp. 572-579.
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Novel findings in microbiology question the long-standing paradigm that a healthy pregnancy implies a sterile uterus. It now seems that the placenta is frequently colonized with bacteria, and a placental microbiome has been identified. Recent literature findings are summarized here, and an attempt is made to separate pathological bacterial presence from a naturally occurring microbiome.
Liu T et al., 2025·iScience·Free full text on PubMed Central
There is growing interest in the use of microbial-seeding interventions to mitigate the impacts of prenatal antibiotics, C-section, and lack of breastfeeding on mother-child microbe sharing. However, the relative importance of maternal vaginal vs. fecal microbiota in this process is unclear. Analyzing 16S rRNA sequences from five US birth cohorts, we found that maternal vaginal and fecal microbiota became more similar as pregnancy progressed, and both niches influenced the child's fecal microbiota. The relative contribution of maternal vaginal microbiota increased when vaginal sampling occurred later in gestation. As children aged from birth to 5 years, their fecal microbiota increasingly resembled their mother's fecal microbiota as compared to vaginal microbiota. Patterns of sharing appeared to differ by prenatal antibiotic use, birth mode (C-section vs. vaginal), and breastfeeding. Our findings enhance understanding of niche-specific mother-child microbe sharing and may inform microbial-seeding interventions. Metagenomic studies are needed to identify specific shared strains.
Premature birth causes high rates of neonatal morbidity and mortality. There are multiple causes of preterm birth. This article reviews the evidence linking subclinical infection and premature birth. Although maternal genital tract colonization with specific organisms has been inconsistently associated with preterm birth and/or premature rupture of membranes, some infections have been consistently associated with preterm delivery. The association of histologic chorioamnionitis with prematurity is a consistent finding, but the mechanisms require further study. The relationship between histologic chorioamnionitis infection and the chorioamnionitis of prematurity requires additional research. A varying number of patients in "idiopathic" preterm labor have positive amniotic fluid cultures (0% to 30%), but it is not clear whether infection preceded labor or occurred as a result of labor. Evidence of subclinical infection as a cause of preterm labor is raised by finding elevated maternal serum C-reactive protein and abnormal amniotic fluid organic acid levels in some patients in preterm labor. Biochemical mechanisms for preterm labor in the setting of infection are suggested by both in vitro and in vivo studies of prostaglandins and their metabolites, endotoxin and cytokines. Some, but by no means all, antibiotic trials conducted to date have reported decreases in prematurity. These results support the hypothesis that premature birth results in part from infection caused by genital tract bacteria. In the next few years, research efforts must be prioritized to determine the role of infection and the appropriate prevention of this cause of prematurity.
Chen C et al., 2017·Nat Commun·Free full text on PubMed Central
Reports on bacteria detected in maternal fluids during pregnancy are typically associated with adverse consequences, and whether the female reproductive tract harbours distinct microbial communities beyond the vagina has been a matter of debate. Here we systematically sample the microbiota within the female reproductive tract in 110 women of reproductive age, and examine the nature of colonisation by 16S rRNA gene amplicon sequencing and cultivation. We find distinct microbial communities in cervical canal, uterus, fallopian tubes and peritoneal fluid, differing from that of the vagina. The results reflect a microbiota continuum along the female reproductive tract, indicative of a non-sterile environment. We also identify microbial taxa and potential functions that correlate with the menstrual cycle or are over-represented in subjects with adenomyosis or infertility due to endometriosis. The study provides insight into the nature of the vagino-uterine microbiome, and suggests that surveying the vaginal or cervical microbiota might be useful for detection of common diseases in the upper reproductive tract.Whether the female reproductive tract harbours distinct microbiomes beyond the vagina has been a matter of debate. Here, the authors show a subject-specific continuity in microbial communities at six sites along the female reproductive tract, indicative of a non-sterile environment.
Vitale SG et al., 2021·International Journal of Molecular Sciences·Free full text on PubMed Central
The human microbiome plays a crucial role in determining the health status of every human being, and the microbiome of the genital tract can affect the fertility potential before and during assisted reproductive treatments (ARTs). This review aims to identify and appraise studies investigating the correlation of genital microbiome to infertility. Publications up to February 2021 were identified by searching the electronic databases PubMed/MEDLINE, Scopus and Embase and bibliographies. Only full-text original research articles written in English were considered eligible for analysis, whereas reviews, editorials, opinions or letters, case studies, conference papers, and abstracts were excluded. Twenty-six articles were identified. The oldest studies adopted the exclusive culture-based technique, while in recent years PCR and RNA sequencing based on 16S rRNA were the most used technique. Regardless of the anatomical site under investigation, the Lactobacillus-dominated flora seems to play a pivotal role in determining fertility, and in particular Lactobacillus crispatus showed a central role. Nonetheless, the presence of pathogens in the genital tract, such as Chlamydia trachomatis, Gardnerella vaginalis, Ureaplasma species, and Gram-negative stains microorganism, affected fertility also in case of asymptomatic bacterial vaginosis (BV). We failed to identify descriptive or comparative studies regarding tubal microbiome. The microbiome of the genital tract plays a pivotal role in fertility, also in case of ARTs. The standardization of the sampling methods and investigations approaches is warranted to stratify the fertility potential and its subsequent treatment. Prospective tubal microbiome studies are warranted.
General Gynecology › Infections › Vaginal and Cervical Infections · Infections and the Reproductive Microbiome › Systemic and Emerging Infections › Infection in Pregnancy
PMID 25273890 25273890 DOI 10.1111/lam.12334 10.1111/lam.12334 Wassenaar et al. 2014, Wassenaar 2014
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Wassenaar, T. M., & Panigrahi, P. (2014). Is a foetus developing in a sterile environment? Letters in Applied Microbiology, 59(6), 572-579. https://doi.org/10.1111/lam.12334
Wassenaar TM, Panigrahi P. Is a foetus developing in a sterile environment? Lett Appl Microbiol. 2014;59(6):572-579. doi:10.1111/lam.12334
Wassenaar, T. M., and P. Panigrahi. "Is a foetus developing in a sterile environment?" Letters in Applied Microbiology, vol. 59, no. 6, 2014, pp. 572-579.
