Reassessing the association between bacterial vaginosis and preterm birth: A systematic review and meta-analysis

BACKGROUND

For the past three decades, researchers have proposed an association between bacterial vaginosis (BV) and preterm birth. This association has been questioned since treating BV with antibiotics during pregnancy hasn't led to a decreased risk of preterm birth.

OBJECTIVE

To re-assess the connection between BV and preterm birth by reviewing existing literature.

SEARCH STRATEGY

A systematic search was conducted on PubMed and Web of Science using the keywords "bacterial vaginosis" and "preterm birth" up to November 2020. The protocol followed PRISMA guidelines and was registered with PROSPERO (CRD42022337806).

SELECTION CRITERIA

Studies were included if they: 1) explored the link BV and preterm birth, 2) used diagnostic criteria based on Nugent, Amsel or Spiegel methods, 3) defined preterm birth at <37, 35, or 32 weeks, and 4) involved patients without impending preterm labor symptoms when sampled.

DATA COLLECTION AND ANALYSIS

Data were extracted and analyzed by region, BV diagnosis method, study period, and quality score.

MAINS RESULTS

A total of 28 studies were included in the analysis (comprising 50,466 patients). There was a significant link between BV and preterm birth, with an overall OR of 1.60 [95% CI, 1.36-1.89]. Heterogeneity was high (I²=67%). The elevated risk remained consistent across geographic areas, diagnostic procedures, study periods, and study quality scale (Newcastle-Ottawa score).

CONCLUSION

Our meta-analysis confirms the association between bacterial vaginosis and preterm birth. However, the connection appears to be weaker than previously documented. This observation may offer insight into the ineffectiveness of BV treatments in reducing preterm birth risk.

The microbiome biomarkers of pregnant women's vaginal area predict preterm prelabor rupture in Western China

Introduction

Intraamniotic infection is crucial in preterm prelabor rupture of membranes(PPROM), a clinical condition resulting from the invasion of vaginal opportunistic microbes into the amniotic cavity. Although previous studies have suggested potential associations between infection and PPROM, the role of vaginalopportunistic bacteria in PPROM has received limited attention.

Methods

This study aimed to confirm the vaginal bacterial etiology of PPROM. We investigated vaginal microbiotas using automatic analysis of vaginal discharge, microbiological tests, and 16s rRNA genehigh-throughput sequencing.

Results

The research findings revealed that the proportion of parabasal epitheliocytes, leukocytes, toxic leukocytes, and bacteria with diameters smaller than 1.5 um was significantly higher in the PPROM group than that in the normal full-term labor (TL) group. The top three vaginal opportunistic bacterial isolates in all participants were 9.47% Escherichia coli, 5.99% Streptococcus agalactiae, and 3.57% Enterococcus faecalis. The bacterial resistance differed, but all the isolates were sensitive to nitrofurantoin. Compared with the vaginal microbiota dysbiosis (VMD) TL (C) group, the VMD PPROM (P) group demonstrated more operational taxonomic units, a high richness of bacterial taxa, and a different beta-diversity index. Indicator species analysis revealed that Lactobacillus jensenii, Lactobacillus crispatus, and Veillonellaceae bacterium DNF00626 were strongly associated with the C group. Unlike the C group, the indicator bacteria in the P group were Enterococcus faecalis, Escherichia coli, and Streptococcus agalactiae.

Discussion

These findings provide solidevidence that an abnormal vaginal microbiome is a very crucial risk factorclosely related to PPROM. There were no unique bacteria in the vaginalmicrobiota of the PPROM group; however, the relative abundance of bacteria inthe abnormal vaginal flora of PPROM pregnancies differed. Antibiotics should bereasonably selected based on drug sensitivity testing. The findings presented in this paper enhance our understanding of Streptococcus agalactiae, Enterococcus faecalis, and Escherichia coli vaginal bacterial etiology of PPROM in Western China.

Risk factors for preterm birth: an umbrella review of meta-analyses of observational studies

BACKGROUND

Preterm birth defined as delivery before 37 gestational weeks is a leading cause of neonatal and infant morbidity and mortality. The aim of this study is to summarize the evidence from meta-analyses of observational studies on risk factors associated with PTB, evaluate whether there are indications of biases in this literature, and identify which of the previously reported associations are supported by robust evidence.

METHODS

We searched PubMed and Scopus until February 2021, in order to identify meta-analyses examining associations between risk factors and PTB. For each meta-analysis, we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. Evidence was graded as robust, highly suggestive, suggestive, and weak.

RESULTS

Eighty-five eligible meta-analyses were identified, which included 1480 primary studies providing data on 166 associations, covering a wide range of comorbid diseases, obstetric and medical history, drugs, exposure to environmental agents, infections, and vaccines. Ninety-nine (59.3%) associations were significant at P < 0.05, while 41 (24.7%) were significant at P < 10-6. Ninety-one (54.8%) associations had large or very large heterogeneity. Evidence for small-study effects and excess significance bias was found in 37 (22.3%) and 12 (7.2%) associations, respectively. We evaluated all associations according to prespecified criteria. Seven risk factors provided robust evidence: amphetamine exposure, isolated single umbilical artery, maternal personality disorder, sleep-disordered breathing (SDB), prior induced termination of pregnancy with vacuum aspiration (I-TOP with VA), low gestational weight gain (GWG), and interpregnancy interval (IPI) following miscarriage < 6 months.

CONCLUSIONS

The results from the synthesis of observational studies suggest that seven risk factors for PTB are supported by robust evidence. Routine screening for sleep quality and mental health is currently lacking from prenatal visits and should be introduced. This assessment can promote the development and training of prediction models using robust risk factors that could improve risk stratification and guide cost-effective preventive strategies.

TRIAL REGISTRATION

PROSPERO 2021 CRD42021227296.

Primary prevention with vaginal chlorhexidine before 16 weeks reduces the incidence of preterm birth: results of the Preterm Labor Prevention Using Vaginal Antiseptics study

BACKGROUND

Preterm labor is one of the leading causes of perinatal death and is currently considered a syndrome with many causes. One of the most important causes of preterm birth is ascending infection from bacterial vaginosis. Chlorhexidine has proven to be effective against bacterial vaginosis and against bacterial biofilms without affecting gestation.

OBJECTIVE

We aimed to evaluate the effectiveness of a universal primary prevention strategy for preterm birth using intravaginal chlorhexidine applied before 16 weeks (Preterm Labor Prevention Using Vaginal Antiseptics study).

STUDY DESIGN

We performed a prospective observational study with 2 cohorts of pregnant women that were assigned either to prevention of preterm birth by means of intravaginal chlorhexidine (Cum Laude Chlorhexidine, chlorhexidine digluconate 0.2%) before 16 weeks (n=413), or to no treatment following the usual hospital protocol (n=704). Primary outcomes were the incidence of spontaneous preterm birth before 34 and 37 weeks; the incidence of preterm birth before 34 and 37 weeks, including inductions for premature rupture of membranes; and the incidence of preterm birth before 34 and 37 weeks, including any indication for termination of pregnancy. Both cohorts were compared using Mann-Whitney and Fisher tests. Finally, a multivariable analysis, including the odds ratio was performed, adjusting for clinical parameters, to evaluate the importance of the different determinants in the prediction of preterm birth.

RESULTS

In pregnancies treated with chlorhexidine, the incidences of spontaneous preterm birth; preterm birth, including induction for premature rupture of membranas; and preterm birth, including any indication for termination of pregnancy were at 34 and 37 weeks: 0% and 0%, 0.24% and 1.69, and 2.90% and 3.15%, respectively; whereas in nontreated pregnancies, these incidences were 9% and 11%, 12% and 23%, and 35% and 43%, respectively. According to the multivariable analysis, the incidence of preterm birth among women treated with chlorhexidine before 16 weeks was halved (Odds ratio, 0.52; P<.05).

CONCLUSION

Universal treatment with vaginal chlorhexidine before 16 weeks reduces the incidence of preterm birth, especially before 34 weeks.

Risk factors for preterm labor: An Umbrella Review of meta-analyses of observational studies

Preterm birth defined as delivery before 37 gestational weeks, is a leading cause of neonatal and infant morbidity and mortality. Understanding its multifactorial nature may improve prediction, prevention and the clinical management. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risks factors associated with PTB, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by robust evidence. We included 1511 primary studies providing data on 170 associations, covering a wide range of comorbid diseases, obstetric and medical history, drugs, exposure to environmental agents, infections and vaccines. Only seven risk factors provided robust evidence. The results from synthesis of observational studies suggests that sleep quality and mental health, risk factors with robust evidence should be routinely screened in clinical practice, should be tested in large randomized trial. Identification of risk factors with robust evidence will promote the development and training of prediction models that could improve public health, in a way that offers new perspectives in health professionals.

Antibiotic use during pregnancy and the risk of preterm birth: a population-based Swedish cohort study

OBJECTIVES

To assess the impact of gestational antibiotics on the risk of preterm birth, since a healthy maternal microbiome may be protective.

METHODS

Population-based cohort study including all first pregnancies in Sweden (2006-16). The association between gestational and recent pre-conception systemic antibiotics and preterm birth was assessed by multivariable logistic regression presented as ORs and 95% CIs, adjusted for comorbidities (hypo- and hyperthyroidism, hypertension, or diabetes mellitus pre-gestation), trimester, antibiotic class and treatment duration.

RESULTS

Compared with non-users, antibiotic exposure was associated with increased risks of preterm birth in mothers with comorbidities (OR = 1.32, 95% CI 1.18-1.48) and without (OR = 1.09, 95% CI 1.06-1.13). Pre-conception use showed no association, while risk was increased for first and second trimester use and decreased for third trimester use. The increased risks were seen for the following antibiotic groups in mothers without and with comorbidities, respectively: macrolides, lincosamides and streptogramins (OR = 1.63, 95% CI 1.45-1.83; OR = 2.48, 95% CI 1.72-3.56); quinolones (OR = 1.60, 95% CI 1.32-1.94; OR = 2.11, 95% CI 1.12-4.03); non-penicillin β-lactams (OR = 1.15, 95% CI 1.07-1.24; OR = 1.39, 95% CI 1.07-1.83); other antibacterials (OR = 1.09, 95% CI 1.03-1.14; 1.38, 95% CI 1.16-1.63); and penicillins (OR = 1.04, 95% CI 1.01-1.08; 1.23, 95% CI 1.09-1.40). Antibiotic indications were not available, which could also affect preterm birth.

CONCLUSIONS

Antibiotic use during pregnancy was associated with an increased risk of preterm birth, especially in mothers with chronic diseases.

Screening for Vaginal and Endocervical Infections in the First Trimester of Pregnancy? A Study That Ignites an Old Debate

Objectives: Vaginal and endocervical infections are considered a global health problem, especially after recent evidence of their association with preterm delivery and other adverse obstetric outcomes. Still, there is no consensus on the efficacy of a screening strategy for these infections in the first trimester of pregnancy. This study evaluated their prevalence and whether screening and treatment resulted as effective in reducing pregnancy and perinatal complications. Methods: A single-center prospective observational study was designed; a sample size of 400 first-trimester pregnant women was established and they were recruited between March 2016–October 2019 at the Puerta de Hierro University Hospital (Spain). They were screened for vaginal and endocervical infections and treated in case of abnormal flora. Pregnancy and delivery outcomes were compared between abnormal and normal flora groups by univariate analysis. Results: 109 patients had an abnormal flora result (27.2%). The most frequently detected infection was Ureaplasma urealyticum (12.3%), followed by Candida spp. (11.8%), bacterial vaginosis (5%), Mycoplasma hominis (1.2%) and Trichomonas vaginalis (0.8%). Patients with abnormal flora had a 5-fold increased risk of preterm premature rupture of membranes (5.3% vs. 1.1% of patients with normal flora, Odds Ratio 5.11, 95% Confidence Interval 1.20–21.71, p = 0.028). No significant differences were observed regarding preterm delivery or neonatal morbidity. Conclusions: Considering the morbimortality related to prematurity and that the results of our study suggest that the early treatment of abnormal flora could improve perinatal outcomes, the implementation of a screening program during the first trimester should be considered.

Systematic review and meta-analysis of the papillomavirus prevalence in breast cancer fresh tissues

BACKGROUND

Although widely studied, the role of HPV in the genesis of breast carcinomas remains elusive due to the diversity of results across studies, possibly caused by the wide methodological heterogeneity, some of them with inadequate methods.

OBJECTIVE

To verify the association between HPV and breast cancer through the meta-analysis of studies that used the best-recognized techniques for viral detection and tissue conservation.

METHODS

A systematic review and meta-analysis restricted to studies that detected HPV by PCR in fresh and frozen tissue from breast cancer were conducted to obtain greater homogeneity. PubMed, Scopus, Science Direct, Cochrane Library, and SciELO were searched until December 14, 2019. Search terms included "breast cancer" and "HPV" without language restrictions. Eleven studies were included in the meta-analysis. The pooled relative risks and 95% confidence interval (95% CI) were calculated, and heterogeneity was assessed using the I-squared (I2).

RESULTS

The selected studies had very low heterogeneity (2%). There is a 2.15 times higher combined relative risk (95% CI = 1.60-2.89) of detecting HPV in breast cancer than in cancer-free breast controls with a statistically significant p-value (p < 0.0001).

CONCLUSION

Our data support the association of DNA-HPV with breast carcinomas. Further studies are needed to find out which breast cancer subtypes this association is most frequent.

Clinical and biochemical markers of spontaneous preterm birth in singleton and multiple pregnancies

AIM

The aim of this study was to compare the clinical characteristics of singleton and twin pregnancies that resulted in spontaneous preterm births (sPTB) and to evaluate the prognostic value of phosphorylated insulin-like growth factor binding protein-1 (phIGFB-1) and placental alpha macroglobulin-1(PAMG-1) for sPTB prediction in symptomatic women.

PATIENTS AND METHODS

The study included 420 women and included two parts. Firstly, we performed a retrospective cohort study comparing pregnancy and neonatal outcomes in 170 women with singleton pregnancies and spontaneous preterm birth before 37 weeks of gestation with 150 women with twin pregnancies who delivered at the same gestational age. In order to obtain the link between clinical and biochemical predictors of preterm labor we organized the second part of the research. The second part was a prospective observational study in 100 women with singleton and twin pregnancies between 24 and 33 + 6 weeks of gestation and symptoms of threatening preterm labor and intact membranes. We assessed the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for phIGFBP-1 and PAMG-1 in terms of sPTB within 7 days and 14 days after testing.

RESULTS

The rate of preterm premature rupture of membranes was higher in singleton pregnancies (67.1 versus 42.8%, p = 0.034). Cervical shortening in multiples was diagnosed at an earlier mean gestational age than in singleton pregnancies (30.1 ± 4.3 versus 35.9 ± 3.1 weeks, p = 0.013). In the singleton pregnancies group, the rate of microbial cervical colonization and the rate of bacterial vaginosis were significantly higher than in twin pregnancies (49.4 versus 15.3%, p < 0.001; 32.9 versus 12.0%, p = 0.007, respectively). Premature twins had a longer oxygen dependency period, while the singletons were more predisposed to infectious morbidity. The study showed low sensitivity of phIGFBP-1 for sPTB, while the sensitivity of the PAMG-1 test was higher (sensitivity 60% and 90% within 7 days after testing and 50 versus 75% within 14 days after testing). Both tests showed a high NPV for sPTB (93.3% for phIGFBP-1 versus 98.9% for PAMG-1). The NPV for preterm labor in twins was also high for both tests (93% for phIGFBP-1 and 96% for PAMG-1).

CONCLUSION

Cervical shortening is the main risk factor of sPTB in women with twin pregnancies; sPTB among singletons is associated with ascendent infection, involving fetal membranes. The PAMG-1 test showed high PPV and NPV for sPTB in symptomatic women and could be a reliable prognostic tool in clinical obstetrics. High NPV was observed for phIGFBP-1 and PAMG-1 in twin pregnancies.

Current Resources for Evidence-Based Practice, March 2020

An extensive review of new resources to support the provision of evidence-based care for women and infants. The current column includes a discussion of the concept of overdiagnosis and implications for research and commentaries on reviews focused on exogenous progestogen to maintain pregnancies and cancer risk among children conceived using fertility treatments.