Oral bacteria in placental tissues: increased molecular detection in pregnant periodontitis patients

The association between periodontal disease and risk of adverse maternal or neonatal outcomes: A systematic review and meta-analysis of analytical observational studies

Background and Aim

The aim of this meta-analysis was to find the association between periodontal disease (PD) and the risk of adverse pregnancy outcomes, including Pre-eclampsia (PE), premature rupture of the amniotic sac, gestational diabetes (GDM), or low birth weight (LBW) in pregnant women, which should be investigated in a systematic meta-analysis.

Methods

Studies that reported the association between PD and pregnancy or neonatal outcomes and were published from January 1990 to December 2022, were identified by an extensive search in PubMed (Medline), Scopus, Web of Sciences, and Medline (Elsevier). After retrieving the studies, the screening stage was performed based on their titles, abstracts, and full texts, and after selecting the final articles, their information was extracted and their quality was assessed using the Newcastle Ottawa Scale checklist.

Results

Pregnant women with PD had a 1.39 higher chance of developing GDM than those who did not have the infection (risk ratio [RR]: 1.39; 95% confidence interval [CI]: 1.21-1.61; I square: 49.67%; p: 0.03). Additionally, the pooled RR of LBW was 2.19, which indicates that pregnant women with PD had a 2.19-fold higher risk of LBW than pregnant women who do not have the infection (RR: 2.19; 95% CI: 1.82-2.64; I square: 0.00%; p: 0.65). The relationship between the risk of PE and the existence of PD was examined in 33 cohort and case-control studies for this meta-analysis. These results were combined, and the pooled RR was 1.43. This indicates that pregnant women with PD are 1.43 times more likely to experience PE than pregnant women without PD (RR: 1.43; 95% CI: 1.32-1.54; I square: 82.64%; p: 0.00).

Conclusion

According to the findings of the current meta-analysis, PD may contribute to a higher risk of poor maternal and newborn outcomes in pregnant women.

Dynamics of oral microbiome acquisition in healthy infants: A pilot study

Objectives

The human oral microbiota is one of the most complex bacterial communities in the human body. However, how newborns initially acquire these bacteria remains largely unknown. In this study, we examined the dynamics of oral microbial communities in healthy infants and investigated the influence of the maternal oral microbiota on the acquisition of the infant's oral microbiota. We hypothesized that the infant oral microbial diversity increases with age.

Methods

One hundred and sixteen whole-salivary samples were collected from 32 healthy infants and their biological mothers during postpartum and 9- and 15-month well-infant visits. Bacterial genomic DNA was extracted and sequenced by Human Oral Microbe Identification using Next Generation Sequencing (HOMINGS) methods. The Shannon index was used to measure the microbial diversity of the infant-mother dyads (alpha diversity). The microbial diversity between the mother-infant dyads (beta-diversity) was calculated using the weighted non-phylogenetic Bray-Curtis distance in QIIME 1.9.1. Core microbiome analysis was performed using MicrobiomeAnalyst software. Linear discriminant analysis coupled with effect size analysis was used to identify differentially abundant features between mother and infant dyads.

Results

A total of 6,870,571 16S rRNA reads were generated from paired mother-infant saliva samples. Overall, oral microbial profiles significantly differed between the mother and infant groups (p < 0.001). The diversity of the salivary microbiomes in the infants increased in an age-dependent manner, whereas the core microbiome of the mothers remained relatively stable during the study period. Breastfeeding and gender did not affect the microbial diversity in infants. Moreover, infants had a greater relative abundance of Firmicutes and a lower abundance of Actinobacteria, Bacteroidetes, Fusobacteria, and Proteobacteria than their mothers. The SparCC correlation analysis demonstrated constant changes in infants' oral microbial community network (p < 0.05).

Conclusions

This study provides new evidence that the oral cavities of infants are colonized by a distinct group of bacterial species at birth. The acquisition and diversity of changes in oral microbial composition are dynamic during the first year of an infant's life. Before reaching the second birthday, the composition of the oral microbial community could be more similar to that of their biological mothers.

Microbial profile of placentas from Tanzanian mothers with adverse pregnancy outcomes and periodontitis

AIM

To investigate microbial profiles in placentas from a population of East African mothers with and without adverse pregnancy outcomes and with regard to their periodontal status.

MATERIAL AND METHODS

Thirty-six placentas from pregnant women from Tanzania were classified into three groups according to both pregnancy outcome and the mother's periodontal health. The microbial composition in each group was then compared using 16S rRNA metagenomics. Additionally, placenta specimens were analyzed histologically for chorioamnionitis by a single pathologist blinded to the clinical data.

RESULTS

The greatest differences were observed in the group of mothers with periodontitis. The microbial load was low in all three groups of mothers. Periodontitis had a notable influence on the structure of the placental microbiota. Three phyla and 44 genera were associated with periodontitis, whereas only the Tenericutes phylum was associated with the adverse pregnancy variable. Streptococcaceae and Mycoplasmataceae families were associated with both periodontitis and adverse pregnancy outcomes. Finally, although the differences for chorioamnionitis were not significant, this intra-amniotic infection was more frequent in the placentas from mothers with periodontitis.

CONCLUSIONS

Our findings suggest that bacteria from the oral cavity may involve the feto-placental unit, and that periodontitis may be a modulating factor of the microbial community present in this niche.

Fulminant Sepsis and Perinatal Death at 23 Weeks Due to Fusobacterium nucleatum

Introduction: Fusobacterium nucleatum is a gram-negative anaerobe, a constituent of the oral microflora, responsible for chronic periodontal diseases. Case Report: We describe a preterm infant with premature rupture of membranes at 23 weeks of gestational age due to F. nucleatum. The newborn died soon after birth. Placental histopathology showed severe necrotizing chorioamnionitis and funisitis with gram-negative bacilli. After autopsy, F. nucleatum was microbiologically isolated from the lung. The mother had dental hygiene 1 day before delivery, presenting mild and diffuse gingivitis. At admission, she had leukocytosis, foul-smelling vaginal discharge, but no fever. Conclusion: This case highlights the possibility of F. nucleatum spreading from oral cavity after a dental procedure to the placenta with chorioamnionitis and fetal infection. This raises the question of whether dental procedures during pregnancy should be accompanied by prophylactic antibiotics.

Insight into the Relationship between Oral Microbiota and the Inflammatory Bowel Disease

Inflammatory bowel disease has been a growing concern of lots of people globally, including both adults and children. As a chronic inflammatory disease of the intestine, even though the etiology of inflammatory bowel disease is still unclear, the available evidence from clinic observations has suggested a close association with microorganisms. The oral microbiota possesses the characteristics of a large number and abundant species, second only to the intestinal microbiota in the human body; as a result, it successfully attracts the attention of researchers. The highly diverse commensal oral microbiota is not only a normal part of the oral cavity but also has a pronounced impact on the pathophysiology of general health. Numerous studies have shown the potential associations between the oral microbiota and inflammatory bowel disease. Inflammatory bowel disease can affect the composition of the oral microbiota and lead to a range of oral pathologies. In turn, there are a variety of oral microorganisms involved in the development and progression of inflammatory bowel disease, including Streptococcus spp., Fusobacterium nucleatum, Porphyromonas gingivalis, Campylobacter concisus, Klebsiella pneumoniae, Saccharibacteria (TM7), and Candida albicans. Based on the above analysis, the purpose of this review is to summarize this relationship of mutual influence and give further insight into the detection of flora as a target for the diagnosis and treatment of inflammatory bowel disease to open up a novel approach in future clinical practice.

Oral bacteria, oral health, and adverse pregnancy outcomes

The link between oral health and adverse pregnancy outcomes has been suggested by numerous epidemiological studies. More recent studies indicate the relationship between severity of periodontal disease and adverse pregnancy outcomes. Two virulence mechanisms are proposed: direct invasion of oral microorganisms or their components into the fetal-placenta unit and inflammatory mediators produced in the oral cavity affecting the fetal-placenta unit. While interventional periodontal therapy still yielded contradictory results, animal studies suggest that maternal supplementation of omega-3 fatty acids protects the fetus by suppressing inflammation as well as bacteria proliferation in the placenta. This article reviews the recent epidemiological, mechanistic, interventional, and therapeutic studies of oral health and adverse pregnancy outcomes.

The evidence for placental microbiome and its composition in healthy pregnancies: A systematic review

OBJECTIVE

To assess the available scientific evidence regarding the placental microbial composition of a healthy pregnancy, the quality of this evidence, and the potential relation between placental and oral microbiome.

MATERIALS AND METHODS

Data sources: MEDLINE and EMBASE up to August 1, 2019.

STUDY ELIGIBILITY CRITERIA

Human subjects; healthy women; term deliveries; healthy normal birth weight; assessment of microorganisms (bacteria) in placental tissue; full research papers in English. The quality of the included studies was assessed by a modified Joanna Briggs Institute checklist for analytical cross-sectional studies.

RESULTS

57 studies passed the inclusion criteria. Of these, 33 had a high risk of quality bias (e.g., insufficient infection control, lack of negative controls, poor description of the healthy cases). The remaining 24 studies had a low (N = 12) to moderate (N = 12) risk of bias and were selected for in-depth analysis. Of these 24 studies, 22 reported microorganisms in placental tissues, where Lactobacillus (11 studies), Ureaplasma (7), Fusobacterium (7), Staphylococcus (7), Prevotella (6) and Streptococcus (6) were among the most frequently identified genera. Methylobacterium (4), Propionibacterium (3), Pseudomonas (3) and Escherichia (2), among others, although frequently reported in placental samples, were often reported as contaminants in studies that used negative controls.

CONCLUSIONS

The results support the existence of a low biomass placental microbiota in healthy pregnancies. Some of the microbial taxa found in the placenta might have an oral origin. The high risk of quality bias for the majority of the included studies indicates that the results of individual papers should be interpreted with caution.

Oral microbiota in the oral-genitourinary axis: identifying periodontitis as a potential risk of genitourinary cancers

Periodontitis has been proposed as a novel risk factor of genitourinary cancers: although periodontitis and genitourinary cancers are two totally distinct types of disorders, epidemiological and clinical studies, have established associations between them. Dysbiosis of oral microbiota has already been established as a major factor contributing to periodontitis. Recent emerging epidemiological evidence and the detection of oral microbiota in genitourinary organs indicate the presence of an oral-genitourinary axis and oral microbiota may be involved in the pathogenesis of genitourinary cancers. Therefore, oral microbiota provides the bridge between periodontitis and genitourinary cancers. We have carried out this narrative review which summarizes epidemiological studies exploring the association between periodontitis and genitourinary cancers. We have also highlighted the current evidence demonstrating the capacity of oral microbiota to regulate almost all hallmarks of cancer, and proposed the potential mechanisms of oral microbiota in the development of genitourinary cancers.

Linking periodontitis and adverse pregnancy outcomes through CD14+ CD16+ monocytes

One of the prevalent medical issues that deserve global attention is adverse pregnancy outcomes and preterm low birth weight deliveries which have a significant impact on neonatal health. Periodontitis has been implicated as a significant risk factor for adverse effects in pregnancy. Elevated levels of periodontal pathogenic bacteria and proinflammatory cytokines which are pathognomonic features of periodontitis are believed to cause placental infection and premature rupture of the amniotic membrane consequently leading to preterm delivery. The role of CD14+CD16+ monocytes as a causal link between periodontitis and adverse pregnancy outcomes has not been researched so far, although an elevation of these cells has been independently demonstrated in both conditions. With the available background information, this hypothesis attempts to derive a mechanistic link between periodontitis and adverse pregnancy outcomes through the participation of CD14+CD16+ monocytes.

Connection between Periodontitis-Induced Low-Grade Endotoxemia and Systemic Diseases: Neutrophils as Protagonists and Targets

Periodontitis is considered a promoter of many systemic diseases, but the signaling pathways of this interconnection remain elusive. Recently, it became evident that certain microbial challenges promote a heightened response of myeloid cell populations to subsequent infections either with the same or other pathogens. This phenomenon involves changes in the cell epigenetic and transcription, and is referred to as ''trained immunity''. It acts via modulation of hematopoietic stem and progenitor cells (HSPCs). A main modulation driver is the sustained, persistent low-level transmission of lipopolysaccharide from the periodontal pocket into the peripheral blood. Subsequently, the neutrophil phenotype changes and neutrophils become hyper-responsive and prone to boosted formation of neutrophil extracellular traps (NET). Cytotoxic neutrophil proteases and histones are responsible for ulcer formations on the pocket epithelium, which foster bacteremia and endoxemia. The latter promote systemic low-grade inflammation (SLGI), a precondition for many systemic diseases and some of them, e.g., atherosclerosis, diabetes etc., can be triggered by SLGI alone. Either reverting the polarized neutrophils back to the homeostatic state or attenuation of neutrophil hyper-responsiveness in periodontitis might be an approach to diminish or even to prevent systemic diseases.

Transfer of oral bacteria to the fetus during late gestation

The fetus develops in a privileged environment, as the placenta serves as both a gateway for nutrients and a barrier for pathogen transfer to the fetus. Regardless, recent evidence suggests the presence of bacterial DNA in both placenta and fetus, and we have reported that DNA and protein from small numbers of bacteria gain access to the fetus from the maternal bloodstream. Other routes of environmental bacterial transfer from the mother to fetus remain unknown, as well as the physiological relevance of their presence. In these experiments, we examine multiple routes by which bacterial cellular components can enter the fetus and the fetal response to influx of bacterial DNA and protein. We inoculated maternal sheep with genetically-labeled S. aureus (Staphylococcus aureus) using three routes: intravenously, orally, and intra-vaginally. The inoculum did not produce sepsis or fever in the ewes, therefore mimicking incidental exposure to bacteria during pregnancy. 3-5 days post inoculation, we assessed the presence of bacterial components in the fetal tissues and analyzed fetal brain tissue to identify any alterations in gene expression. Our results demonstrate that components of bacteria that were introduced into the maternal mouth were detected in the fetal brain and that they stimulated changes in gene expression. We conclude that an oral route of transmission is relevant for transfer of bacterial cellular components to the fetus.

NETs Are Double-Edged Swords with the Potential to Aggravate or Resolve Periodontal Inflammation

Periodontitis is a general term for diseases characterised by inflammatory destruction of tooth-supporting tissues, gradual destruction of the marginal periodontal ligament and resorption of alveolar bone. Early-onset periodontitis is due to disturbed neutrophil extracellular trap (NET) formation and clearance. Indeed, mutations that inactivate the cysteine proteases cathepsin C result in the massive periodontal damage seen in patients with deficient NET formation. In contrast, exaggerated NET formation due to polymorphonuclear neutrophil (PMN) hyper-responsiveness drives the pathology of late-onset periodontitis by damaging and ulcerating the gingival epithelium and retarding epithelial healing. Despite the gingival regeneration, periodontitis progression ends with almost complete loss of the periodontal ligament and subsequent tooth loss. Thus, NETs help to maintain periodontal health, and their dysregulation, either insufficiency or surplus, causes heavy periodontal pathology and edentulism.

Do the clinical criteria used to diagnose periodontitis affect the association with prematurity?

In recent years, several studies have examined the possible relationship between periodontal disease in pregnant women and preterm birth. One of the difficulties facing these studies is the heterogeneity of the clinical criteria used to define periodontitis. The aim of this cross-sectional study was to determine the degree of association between maternal periodontitis and preterm birth according to different consensus definitions of periodontal disease. In a study of 146 mothers (60 with preterm births and 86 with term deliveries) at the Sant Joan de Déu Maternal and Children's Hospital in Barcelona, a periodontal examination was carried out within 2 days of birth and the presence of periodontal disease was evaluated using the main clinical classifications published in the literature. The prevalence of periodontitis ranged from 25.4 to 52.1%, depending on the criteria used for its definition. Using the most restrictive criteria, pregnant women with periodontitis had a higher risk of preterm birth (OR: 7.49; p < 0.001) and premature rupture of membranes (OR: 2.49; p = 0.017). Premature infants born to mothers with periodontitis presented a tendency toward low weight, adjusted for gestational age (OR: 3.32; p = 0.065). Our findings suggest that the association between periodontitis and preterm birth is influenced by the definitions of periodontitis used.

Periodontal disease and adverse pregnancy outcomes

Periodontal diseases are considered not only to affect tooth-supporting tissues but also to have a cause-and-effect relationship with various systemic diseases and conditions, such as adverse pregnancy outcomes. Mechanistic studies provide strong evidence that periodontal pathogens can translocate from infected periodontium to the feto-placental unit and initiate a metastatic infection. However, the extent and mechanisms by which metastatic inflammation and injury contribute to adverse pregnancy outcomes still remain unclear. The presence of oral bacteria in the placenta of women with term gestation further complicates our understanding of the biology behind the role of periodontal pathogens in pregnancy outcomes. Epidemiological studies demonstrate many methodological inconsistencies and flaws that render comparisons difficult and conclusions insecure. Therefore, despite the fact that a number of prospective studies show a positive association between periodontal diseases and various adverse pregnancy outcomes, the evidence behind it is still weak. Future well-designed explanatory studies are necessary to verify this relationship and, if present, determine its magnitude. The majority of high-quality randomized controlled trials reveal that nonsurgical periodontal therapy during the second trimester of gestation does not improve pregnancy outcomes. From a biological standpoint, this can be partially explained by the fact that therapy rendered at the fourth to sixth months of pregnancy is too late to prevent placental colonization by periodontal pathogens and consequently incapable of affecting pathogen-induced injury at the feto-placental unit. Thus, interventions during the preconception period may be more meaningful. With the increase in our understanding on the potential association between periodontal disease and adverse pregnancy outcomes, it is clear that dental practitioners should provide periodontal treatment to pregnant women that is safe for both the mother and the unborn child. Although there is not enough evidence that the anti-infective therapy alters pregnancy outcomes, it improves health-promoting behavior and periodontal condition, which in turn advance general health and risk factor control.

The periodontopathic bacteria in placenta, saliva and subgingival plaque of threatened preterm labor and preterm low birth weight cases: a longitudinal study in Japanese pregnant women

OBJECTIVES

This study determined the quantity of periodontopathic bacteria in saliva, subgingival plaque, and placenta on the threatened preterm labor (TPL) and preterm low birth weight (PLBW) subjects in order to identify specific periodontal pathogens with high association to adverse pregnancy outcomes.

METHODS

We used real-time PCR with TaqMan probe and ELISA to detect the amount of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, and Prevotella intermedia in subgingival plaque, saliva, and placenta tissue, in addition to serum IgG titers against these bacteria in 28 patients with TPL and 36 healthy pregnant women.

RESULTS

Thirteen of 64 births delivered PLBW infants. All 6 periodontopathic bacteria were detected in the placenta samples. The amount of F. nucleatum and detection frequency of T. denticola in placental samples was significantly higher in the TPL group than in the healthy group. Meanwhile, the age, anti-P. gingival IgG in serum, amount of P. gingivalis and T. forsythia in plaque samples, detection frequency of P. intermedia in saliva, and percentage of pocket probing depth ≥ 5 mm were higher in TPL-PLBW births than those in TPL-Healthy delivery (HD) group and/or in H-HD group. Ordinal logistic regression analysis revealed that the presence of F. nucleatum in placental tissues was significantly associated with TPL, while the maternal age was significantly associated with PLBW in TPL.

CONCLUSION

Our findings suggested all 6 bacteria may access the placenta. The increased presence of F. nucleatum in placenta might be related to TPL, while advanced maternal age might be associated with PLBW in TPL.

CLINICAL RELEVANCE

Periodontal therapy should be applied to reduce the deep periodontal pocket sites and the colonization of periodontal pathogens in high-risk population.

Placental colonization with periodontal pathogens: the potential missing link

Observational studies demonstrate that women with severe periodontitis have a higher risk of adverse pregnancy outcomes like preterm birth and low birthweight. Standard treatment for periodontitis in the form of scaling and root planing during the second trimester failed to reduce the risk of preterm or low birthweight. It is premature to dismiss the association between periodontitis and adverse pregnancy outcomes because one explanation for the failure of scaling and root planing to reduce the risk of adverse pregnancy outcomes is that periodontal pathogens spread to the placental tissue prior to periodontal treatment. In the placenta, orally derived organisms could cause direct tissue damage or mediate a maternal immune response that impairs the growth of the developing fetus. Sequencing studies demonstrate the presence of organisms derived from the oral microbiome in the placenta, but DNA-based sequencing studies should not be the only technique to evaluate the placental microbiome because they may not detect important shifts in the metabolic capability of the microbiome. In humans, polymerase chain reaction and histology have detected periodontal pathogens in placental tissue in association with multiple adverse pregnancy outcomes. We conclude that both placental and oral microbiomes may play a role in periodontitis-associated adverse pregnancy outcomes. However, the measure to determine the association between periodontal pathogens in the placenta and adverse pregnancy outcomes should be the amount and prevalence, not the mere presence of such microorganisms. Placental colonization with periodontal pathogens thus potentially represents the missing link between periodontitis and adverse pregnancy outcomes.

Population-Based Estimation of Dental Caries and Periodontal Disease Rates of Gravid and Recently Postpartum Women in Lilongwe, Malawi

Objectives  The objective of this study was to determine the rate of dental caries and periodontal disease among gravid and recently postpartum women at five delivery centers within and surrounding Lilongwe, Malawi. Study Design  We partnered with obstetric specialists, community health workers, and dentists to perform dental history interviews and dental examinations during the study period from December 2012 to May 2014. Dental examinations were performed according to World Health Organization standards to assess periodontal and oral health status. Results  Among the 387 gravid and recently postpartum women, the rate of dental caries was 69.3% and the rate of composite dental disease (caries and periodontal disease) was 76.7%. The majority (69.5%) of women examined had a decayed-missing-filled (DMF) index greater than or equal to one; the average DMF Index was 2.48. The majority of women had never seen a dentist (62.8%). However, most did perform oral hygiene, two or more times per day (90.2%); most women reported brushing with toothpaste (88.1%). Conclusion  When assessing this population for dental caries and periodontal disease, the rate of dental disease was high. Therefore, this may be an ideal setting to test for impactful interventions aimed at reducing caries and periodontal disease.

Talk to your gut: the oral-gut microbiome axis and its immunomodulatory role in the etiology of rheumatoid arthritis

Microbial communities inhabiting the human body, collectively called the microbiome, are critical modulators of immunity. This notion is underpinned by associations between changes in the microbiome and particular autoimmune disorders. Specifically, in rheumatoid arthritis, one of the most frequently occurring autoimmune disorders worldwide, changes in the oral and gut microbiomes have been implicated in the loss of tolerance against self-antigens and in increased inflammatory events promoting the damage of joints. In the present review, we highlight recently gained insights in the roles of microbes in the etiology of rheumatoid arthritis. In addition, we address important immunomodulatory processes, including biofilm formation and neutrophil function, which have been implicated in host-microbe interactions relevant for rheumatoid arthritis. Lastly, we present recent advances in the development and evaluation of emerging microbiome-based therapeutic approaches. Altogether, we conclude that the key to uncovering the etiopathogenesis of rheumatoid arthritis will lie in the immunomodulatory functions of the oral and gut microbiomes.

The association between periodontal disease and adverse pregnancy outcomes in Northern Tanzania: a cross-sectional study

Background

For the past two decades, studies have investigated the relationship between periodontal disease and adverse pregnancy outcomes such as pre-eclampsia, preterm birth, low birth weight and preterm premature rupture of membranes.

Objectives

To determine the prevalence of periodontal disease and associated adverse pregnancy outcomes among women delivering at the Kilimanjaro Christian Medical Centre (KCMC).

Methods

This cross-sectional study was based on the use of patients' files, clinical examinations and oral interviews with mothers who delivered at the KCMC. Pregnant women with singleton babies (N=1117) who delivered at the KCMC were recruited for the study. Intra-oral examination was performed within five days of birth. The Community Periodontal Index was used to assess periodontal disease

Results

The prevalence of periodontal disease was 14.2%. Periodontal disease was significantly associated with higher odds of pre-eclampsia [adjusted Odds Ratio 95% Confidence Interval (aOR=4.12;95%CI:2.20–7.90)], low birth weight (aOR=2.41;95%-CI:1.34–4.33) and preterm birth (aOR=2.32;95%CI:1.33–4.27). There was no significant association between periodontal disease and preterm premature rupture of membranes (aORs 1.83;95%CI:0.75–4.21) and eclampsia (3.71;95%CI:0.80–17.13).

Conclusion

Maternal periodontal disease is a potential independent risk indicator for pre-eclampsia, low birth weight, and preterm birth. Periodontal assessment and therapy should form part of the preventive antenatal care provided to women in developing countries.

Periodontal Disease and Pregnancy Outcomes: Overview of Systematic Reviews

Periodontal disease is very common during pregnancy. Although it has been linked to adverse pregnancy outcomes, systematic reviews have reached discrepant conclusions on these links. Therefore, we conducted a systematic overview of systematic reviews studying the association between periodontal disease and adverse pregnancy outcomes. We searched 6 online databases up to November 2016 and hand-searched references and citations of eligible papers. Systematic reviews of studies comparing pregnancy outcomes among women with and without periodontal disease were eligible for inclusion. Primary outcomes were maternal mortality, preterm birth, and perinatal mortality. Two reviewers extracted data and assessed risk of bias of individual systematic reviews. Findings are described in tabular and narrative form. Twenty-three systematic reviews (including between 3 and 45 studies) were included. None reported the association between periodontal disease and maternal or perinatal mortality. Systematic reviews with the lowest risk of bias consistently demonstrated positive associations between periodontal disease and preterm birth (relative risk, 1.6; 95% confidence interval, 1.3 to 2.0; 17 studies, 6,741 participants), low birth weight (LBW; relative risk, 1.7; 95% CI, 1.3 to 2.1; 10 studies, 5,693 participants), preeclampsia (odds ratio, 2.2; 95% CI, 1.4 to 3.4; 15 studies, 5,111 participants), and preterm LBW (relative risk 3.4; 95% CI, 1.3 to 8.8; 4 studies, 2,263 participants). Based on these figures, estimated population-attributable fractions for periodontal disease were 5% to 38% for preterm birth, 6% to 41% for LBW, and 10% to 55% for preeclampsia. In terms of limitations, as several primary studies did not adjust for confounding, meta-analyses may have overestimated the strength of the associations under study. Due to substantial overlap in included primary studies, we could not aggregate results across reviews. Consistent evidence from systematic reviews with low risk of bias indicates that pregnant women with periodontal disease are at increased risk of developing preeclampsia and delivering a preterm and/or LBW baby (PROSPERO: CRD42015030132).

Knowledge Transfer Statement: This study highlights that periodontal disease is an important risk factor for several common adverse pregnancy outcomes. Clinicians should be aware of this link to guide risk selection. Research is needed to develop novel preventive and treatment strategies.

Porphyromonas gingivalis and adverse pregnancy outcome

Porphyromonas gingivalis is a Gram-negative, anaerobic bacterium considered to be an important pathogen of periodontal disease that is also implicated in adverse pregnancy outcome (APO). Until recently, our understanding of the role of P. gingivalis in APO has been limited and sometimes contradictory. The purpose of this review is to provide an overview of past and current research on P. gingivalis that addresses some of the controversies concerning the role of this organism in the pathogenesis of APO.

Association of periodontitis with preterm birth and low birth weight: a comprehensive review

It is estimated that six million perinatal deaths occur every year worldwide, with premature birth being the main cause. Scientific evidence has shown that there is an association between periodontal health during pregnancy and adverse outcomes of labor, although interventional studies based on the treatment of periodontitis have failed to document an impact on reducing the incidence of preterm birth (PB) or low birth weight (LBW). Two pathogenic mechanisms have been proposed to explain this association. The direct pathway is based on the presence of gram-negative anaerobic bacteremia originating in the gingival biofilm, whereas the indirect pathway involves the production of pro-inflammatory markers which enter the bloodstream from the gingival submucosa. The result is the same: the development of an immune inflammatory response and/or the local suppression of growth factors in the fetal-placental unit, which in turn triggers labor. In the present review, we describe current concepts pertinent to PB and LBW, chronic and aggressive periodontitis, and the most frequent aspects of periodontal pathology during pregnancy. We evaluate the scientific evidence available to date, and offer a detailed description of the two pathways proposed to explain the association of maternal periodontitis with preterm and LBW delivery.

Role of Maternal Periodontitis in Preterm Birth

In the last two decades, many studies have focused on whether periodontitis is a risk factor for preterm birth (PTB). However, both epidemiological investigation and intervention trials have reached contradictory results from different studies. What explains the different findings, and how should future studies be conducted to better assess this risk factor? This article reviews recent epidemiological, animal, and in vitro studies as well as intervention trials that evaluate the link between periodontitis and PTB. Periodontitis may act as a distant reservoir of microbes and inflammatory mediators and contribute to the induction of PTB. Animal studies revealed that maternal infections with periodontal pathogens increase levels of circulating IL-1β, IL-6, IL-8, IL-17, and TNF-α and induce PTB. In vitro models showed that periodontal pathogens/byproducts induce COX-2, IL-8, IFN-γ, and TNF-α secretion and/or apoptosis in placental tissues/cells. The effectiveness of periodontal treatment to prevent PTB is influenced by the diagnostic criteria of periodontitis, microbial community composition, severity of periodontitis, treatment strategy, treatment efficiency, and the period of treatment during pregnancy. Although intervention trials reported contradictory results, oral health maintenance is an important part of preventive care that is both effective and safe throughout pregnancy and should be supported before and during pregnancy. As contradictory epidemiological and intervention studies continue to be published, two new ideas are proposed here: (1) severe and/or generalized periodontitis promotes PTB and (2) periodontitis only promotes PTB for pregnant women who are young or HIV-infected or have preeclampsia, pre-pregnancy obesity, or susceptible genotypes.