Vaginal microbiota in pregnancy: Role in induction of labor and seeding the neonate’s microbiota? (original) (raw)

The vaginal microbiota during pregnancy

Records of Pharmaceutical and Biomedical Sciences

Fetal development is considered to occur inside the microbiotafree intrauterine environment. Depending on recently published data resources, it is anticipated that the neonatal microbiome is established primarily throughout the amniotic membrane rupture, with extra microbiota introduced by the passage of he t fetus through the vaginal birth canal. Upon delivery, the neonate has been familiarized with the maternal microbiota of the vaginal ecosystem. Since the fetus is introduced to numerous bacterial environments during the early neonatal interval such as the vaginal canal, skin, and rectum, it is important to describe the potential influence of the maternal vaginal microbial community on neonates. Dynamic changes in the vaginal microbiome during the pregnancy including decreased vaginal diversity and Lactobacillus-dominance contribute to diminished risk of preterm birth as well as other adverse pregnancy outcomes. This minireview summarizes the composition of the vaginal microbiota during normal pregnancy as revealed by culture-independent highthroughput sequencing-based techniques such as 16S rRNA nextgeneration sequencing and metagenomic shotgun sequencing techniques.

The vaginal microbiome and preterm birth

Nature Medicine

pproximately 15 million preterm births at less than 37 weeks of gestation occur annually worldwide 1. Preterm birth (PTB) remains the second most common cause of neonatal death across the globe, and the most common cause of infant mortality in middle-and high-income economies 2. The consequences of PTB persist from early childhood into adolescence and adulthood 3,4. In the United States, striking population differences with respect to PTB exist, with women of African ancestry having a substantially larger burden of risk. The estimated annual cost of PTB in the United States alone is over US$26.2 billion 5. Despite these statistics, there remains a paucity of effective strategies for predicting and preventing PTB. Although maternal and fetal genetics, and gene-environment interactions, clearly play roles in determining the length of gestation, environmental factors, including the microbiome, are the most important contributors to PTB, particularly among women of African ancestry 6. Microbe-induced inflammation resulting from urinary tract infection, sexually transmitted infections, including trichomoniasis, or bacterial vaginosis is thought to be a cause of PTB 7,8. Ascension of microbes 7,9 from the lower reproductive tract to the placenta, fetal membranes and uterine cavity, and hematogenous spread of periodontal pathogens from the mouth, have also been invoked to explain the up to 40-50% of preterm births that are associated with microbial etiologies 10,11. A homogeneous Lactobacillus-dominated microbiome has long been considered the hallmark of health in the female reproductive tract. In contrast, a vaginal microbiome with high species diversity, as observed with bacterial vaginosis, has been associated with increased risk for acquisition and transmission of sexually

Characterisation of the vaginal Lactobacillus microbiota associated with preterm delivery

Scientific Reports, 2014

The presence of an abnormal vaginal microflora in early pregnancy is a risk factor for preterm delivery. There is no investigation on vaginal flora dominated by lactic acid bacteria and possible association with preterm delivery. We assessed the dominant vaginal Lactobacillus species in healthy pregnant women in early pregnancy in relation to pregnancy outcome. We observed 111 low risk pregnant women with a normal vaginal microflora 11 1 0 to 14 1 0 weeks of pregnancy without subjective complaints. Vaginal smears were taken for the identification of lactobacilli using denaturing gradient gel electrophoresis (DGGE). Pregnancy outcome was recorded as term or preterm delivery (limit 36 1 6 weeks of gestation). The diversity of Lactobacillus species in term vs. preterm was the main outcome measure. L. iners alone was detected in 11 from 13 (85%) women who delivered preterm. By contrast, L. iners alone was detected in only 16 from 98 (16%) women who delivered at term (p , 0.001). Fifty six percent women that delivered at term and 8% women that delivered preterm had two or more vaginal Lactobacillus spp. at the same time. This study suggests that dominating L. iners alone detected in vaginal smears of healthy women in early pregnancy might be associated with preterm delivery. OPEN SUBJECT AREAS: OUTCOMES RESEARCH MEDICAL RESEARCH

The vaginal microbiome during pregnancy and the postpartum period in a European population

Scientific reports, 2015

The composition and structure of the pregnancy vaginal microbiome may influence susceptibility to adverse pregnancy outcomes. Studies on the pregnant vaginal microbiome have largely been limited to Northern American populations. Using MiSeq sequencing of 16S rRNA gene amplicons, we characterised the vaginal microbiota of a mixed British cohort of women (n = 42) who experienced uncomplicated term delivery and who were sampled longitudinally throughout pregnancy (8-12, 20-22, 28-30 and 34-36 weeks gestation) and 6 weeks postpartum. We show that vaginal microbiome composition dramatically changes postpartum to become less Lactobacillus spp. dominant with increased alpha-diversity irrespective of the community structure during pregnancy and independent of ethnicity. While the pregnancy vaginal microbiome was characteristically dominated by Lactobacillus spp. and low alpha-diversity, unlike Northern American populations, a significant number of pregnant women this British population had ...

Racioethnic diversity in the dynamics of the vaginal microbiome during pregnancy

Nature Medicine

rowing evidence suggests that the impact of the vaginal microbiome extends to the health of pregnant women and their neonates in utero and beyond. The vaginal microbiome consists of a finite number of discrete microbial communities dominated by different bacterial taxa or combinations thereof 1,2. A vaginal microbiome with microbial communities dominated by species of Lactobacillus has been associated with adverse conditions of health of the female reproductive tract, whereas a microbiome dominated by complex microbial communities of Gardnerella, Atopobium, Dialister, Peptoniphilus, Lachnospiraceae members (bacterial vaginosis (BV)-associated bacterium 1 (BVAB1)) and other anaerobes 3-5 has been associated with a higher risk. A complex vaginal microbiome is associated with BV, the most common gynecological condition of women of reproductive age 6 , as well as a higher risk of sexually transmitted infection, pelvic inflammatory disease and adverse pregnancy outcomes including preterm birth (PTB) 3,5,7. More than 10% of neonates in the United States are delivered preterm (<37 weeks' gestation), and certain racial and ethnic groups have even higher rates 8-10. Women of African ancestry in the United States are significantly more likely than women of European ancestry to have a premature birth or experience very preterm delivery (<32 weeks' gestation). This health disparity could be due to differences in the vaginal microbiomes of these women as the population attributable risk of BV for spontaneous PTB at <32 weeks' gestation has been estimated to be ~40% 11. Although environmental factors, including socioeconomic status (for example, household income, access to care and so on) are known to contribute to these differences, genetic factors also play a role 12-14. Recent studies 1,2,15-23 show that the vaginal microbiomes of women of African ancestry are less likely to be dominated by species of Lactobacillus, and more likely to comprise primarily Gardnerella vaginalis, Atopobium vaginae, Sneathia amnii, BVAB1 and other anaerobes. Independent of the

The vaginal microbiome and the risk of preterm birth: a systematic review and network meta-analysis

Scientific Reports

Preterm birth is a major cause of neonatal morbidity and mortality worldwide. Increasing evidence links the vaginal microbiome to the risk of spontaneous preterm labour that leads to preterm birth. The aim of this systematic review and network meta-analysis was to investigate the association between the vaginal microbiome, defined as community state types (CSTs, i.e. dominance of specific lactobacilli spp, or not (low-lactobacilli)), and the risk of preterm birth. Systematic review using PubMed, Web of Science, Embase and Cochrane library was performed. Longitudinal studies using culture-independent methods categorizing the vaginal microbiome in at least three different CSTs to assess the risk of preterm birth were included. A (network) meta-analysis was conducted, presenting pooled odds ratios (OR) and 95% confidence intervals (CI); and weighted proportions and 95% CI. All 17 studies were published between 2014 and 2021 and included 38–539 pregnancies and 8–107 preterm births. Wome...

New Techniques to characterise the vaginal microbiome in pregnancy

AIMS Microbiology, 2016

Understanding of the vaginal microbiome in health and disease is essential to screen, detect and manage complications in pregnancy. One of the major complications of pregnancy is preterm birth, which is the leading worldwide cause of death and disability in children under five years of age. The aetiology of preterm birth is multifactorial, but a causal link has been established with infection. Despite the importance of understanding the vaginal microbiome in pregnancy in order to evaluate strategies to prevent and manage PTB, currently used culture based techniques provide limited information as not all pathogens are able to be cultured. The implementation of culture-independent high-throughput techniques and bioinformatics tools are advancing our understanding of the vaginal microbiome. New methods employing 16S rRNA and metagenomics analyses make possible a more comprehensive description of the bacteria of the human microbiome. Several studies on the vaginal microbiota of pregnant women have identified a large number of taxa. Studies also suggest reduced diversity of the microbiota in pregnancy compared to non-pregnant women, with a relative enrichment of the overall abundance of Lactobacillus species, and significant differences in the diversity of Lactobacillus spp. A number of advantages and disadvantages of these techniques are discussed briefly. The potential clinical importance of the new techniques is illustrated through recent reports where traditional culture-based techniques failed to identify pathogens in high risk complicated 56 AIMS Microbiology Volume 2, Issue 1, 55-68. pregnancies whose presence subsequently was established using culture-independent, highthroughput analyses.