Inflammatory Proteins in the Amniotic Fluid, Plasma, and Cervicovaginal Fluid for the Prediction of Intra-Amniotic Infection/Inflammation and Imminent Preterm Birth in Preterm Labor

Absolute counts of leukocyte subsets in peripheral blood in pregnancies complicated by preterm prelabour rupture of membranes

BACKGROUND

This study aimed to assess variations in the absolute counts of various leukocyte subsets in the peripheral blood of women with pregnancies affected by preterm prelabour rupture of membranes (PPROM), in relation to the presence of intra-amniotic inflammation (IAI).

METHODS

The study included fifty-two women with singleton pregnancies experiencing PPROM. Absolute counts of different leukocyte subpopulations, such as granulocytes, monocytes, lymphocytes, T cells and their subsets, B cells and their subsets, and NK cells and their subsets, were measured in maternal peripheral blood samples using multicolour flow cytometry. IAI was identified by elevated concentrations of interleukin 6 (IL-6) in the amniotic fluid, which was collected through transabdominal amniocentesis.

RESULTS

Women with IAI exhibited higher absolute counts of leukocytes (p = 0.003), granulocytes (p = 0.008), and monocytes (p = 0.009). However, the presence of IAI did not significantly affect the absolute counts of lymphocytes or their subpopulations.

CONCLUSIONS

The study found that IAI is associated with changes in the absolute counts of leukocytes from the innate immunity compartment in the peripheral blood of women with pregnancies complicated by PPROM. Conversely, it does not significantly alter the counts of cells from the adaptive immune system. The changes observed may reflect the natural, temporal, and localised characteristics of IAI.

Correlation of amniotic fluid inflammatory markers with preterm birth: a meta-analysis

BACKGROUND

The relationship between amniotic fluid inflammatory biomarkers and preterm birth in second- or third-trimester pregnancy has been a focus, and understanding the correlation between these markers and preterm birth is important for early identification and intervention in preterm birth. The aim of this study was to explore potential inflammatory biomarkers in second- or third-trimester pregnancy amniotic fluid associated with preterm birth.

METHODS

On November 30, 2023, we searched literature involved the influence of second- or third-trimester pregnancy amniotic fluid inflammatory biomarkers on preterm birth through PubMed, Web of Science, Embase, Scope, CNKI, WanFang, VIP and China Biomedical Databases. The search languages were Chinese and English. Included outcomes indexes were combined utility analysis via R software.

RESULTS

A total of 11 articles were included in the combined utility analysis. This combined analysis revealed significant differences in several inflammatory biomarkers in amniotic fluid between the two groups (MD = 6.87, 95%CI: 0.26 - 13.47, P < 0.01); the difference in amniotic fluid IL-6 between the two groups (MD = 5.73, 95%CI: 3.13-8.32, P < 0.01); the difference in amniotic fluid IL-10 between the two groups (MD = 0.11, 95%CI: -3.26-3.48, P < 0.01); the difference in amniotic fluid CRP between the two groups (MD = 21.34, 95%CI: 11.69-30.89, P < 0.01); the difference in amniotic fluid MCP-1 between the two groups (MD = 312.14, 95%CI: 211.34-412.97, P < 0.01); the difference in the amniotic fluid MMP-9 between the two groups (MD = 0.86, 95%CI: -0.10-1.82, P < 0.01); and the difference in TNF-α in amniotic fluid between the two groups (MD = 22.78, 95%CI: -5.05-50.61, P < 0.01).

CONCLUSIONS

The inflammatory biomarkers IL-1β, IL-6, IL-10, CRP, TNFα, MCP-1 and MMP-9 in the amniotic fluid of patients in the second- or third-trimester pregnancy were all correlated with preterm birth.

Predictive potential of various plasma inflammation-, angiogenesis-, and extracellular matrix remodeling-associated mediators for intra-amniotic inflammation and/or microbial invasion of the amniotic cavity in preterm labor

PURPOSE

To determine whether various inflammatory-, angiogenic/anti-angiogenic-, and extracellular matrix remodeling-associated proteins in plasma, alone or in combination with conventional blood-based markers, can predict intra-amniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) in women with spontaneous preterm labor (PTL).

METHODS

A total of 193 singleton pregnant women with PTL (23-33 weeks) were included in this retrospective cohort study. Plasma samples were obtained at the time of amniocentesis. Amniotic fluid (AF) was cultured for microorganism detection and consequent MIAC diagnosis. IL-6 levels were determined in AF and used to identify IAI (AF IL-6 ≥ 2.6 ng/mL). Endostatin, haptoglobin, IGFBP-2/3, LBP, M-CSF, MMP-2/8, pentraxin 3, PlGF, S100A8/A9, and VEGFR-1 levels were assayed in plasma samples by ELISA. CRP levels and neutrophil-to-lymphocyte ratio (NLR) were measured.

RESULTS

Plasma LBP, MMP-8, and S100A8/A9 levels, CRP levels, and NLR were significantly higher, and plasma IGFBP-2 and MMP-2 levels were significantly lower in women with IAI/MIAC than in those without this condition, whereas no baseline variables differed significantly between the two groups. Using a stepwise regression analysis, a noninvasive prediction model for IAI/MIAC was developed, which included plasma LBP, MMP-2, and MMP-8 levels (area under the curve [AUC], 0.785). The AUC for this prediction model was significantly or borderline greater than that of any single factor included in the model.

CONCLUSIONS

IGFBP-2, LBP, MMP-2, MMP-8, and S100A8/A9 may represent valuable plasma biomarkers for predicting IAI/MIAC in women with PTL. Combination of LBP, MMP-2, and MMP-8 expression data can significantly improve the predictive potential for IAI/MIAC.

Identification and characterization of plasma proteins associated with intra-amniotic inflammation and/or infection in women with preterm labor

This study aimed to identify plasma proteins that could serve as potential biomarkers for microbial invasion of the amniotic cavity (MIAC) or intra-amniotic inflammation (IAI) in women with preterm labor (PTL). A retrospective cohort comprised singleton pregnant women with PTL (24-34 weeks) who underwent amniocentesis. Pooled plasma samples were analyzed by label-free liquid chromatography-tandem mass spectrometry for proteome profiling in a nested case-control study (concomitant MIAC/IAI cases vs. non-MIAC/IAI controls [n = 10 per group]). Eight target proteins associated with MIAC/IAI were further verified by immunoassays in a large cohort (n = 230). Shotgun proteomic analysis revealed 133 differentially expressed proteins (fold change > 1.5, P < 0.05) in the plasma of MIAC/IAI cases. Further quantification confirmed that the levels of AFP were higher and those of kallistatin and TGFBI were lower in the plasma of women with MIAC and that the levels of kallistatin and TGFBI were lower in the plasma of women with IAI than in those without these conditions. The area under the curves of plasma AFP, kallistatin, and TGFBI ranged within 0.67-0.81 with respect to each endpoint. In summary, plasma AFP, kallistatin, and TGFBI may represent valuable non-invasive biomarkers for predicting MIAC or IAI in women with PTL.

Amniotic fluid CD36 in pregnancies complicated by spontaneous preterm delivery: a retrospective cohort study

OBJECTIVE

The aim of this study was to evaluate CD36 concentrations in amniotic fluid in pregnancies complicated by spontaneous delivery with intact fetal membranes (preterm labor, PTL) and preterm prelabor rupture of membranes (PPROM) with respect to the presence of the intra-amniotic infection.

METHODS

A total of 80 women with PPROM and 71 with PTL were included in the study. Amniotic fluid samples were obtained by transabdominal amniocentesis. Amniotic fluid CD36 concentrations were assessed by enzyme-linked immunosorbent assay. Microbial colonization of the amniotic cavity (MIAC) was determined by the cultivation and non-cultivation approach. Intra-amniotic inflammation (IAI) was defined as an amniotic fluid bedside interleukin-6 concentration ≥3000 pg/mL. Intra-amniotic infection was characterized by the presence of both MIAC and IAI.

RESULTS

Women with PPROM with intra-amniotic infection had higher amniotic fluid CD36 concentrations than women without infection (with infection: median 346 pg/mL, IQR 262-384 vs. without infection: median 242 pg/mL, IQR 199-304; p = .006) A positive correlation between amniotic fluid CD36 concentrations and interleukin-6 concentrations was found (rho = 0.48; p < .0001). In PTL pregnancies, no statistically significant difference was found in the amniotic fluid level of CD36 between intra-amniotic infection, sterile IAI, and negative amniotic fluid.

CONCLUSIONS

The presence of intra-amniotic infection is characterized by higher amniotic fluid CD36 concentrations in pregnancies complicated by PPROM. An amniotic fluid CD36 cutoff value of 252.5 pg/mL was found to be optimal for the prediction of intra-amniotic infection. In PTL pregnancies, no statistically significant change in CD36 concentration was found with respect to the presence of intra-amniotic infection.

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.

Extracellular matrix-related and serine protease proteins in the amniotic fluid of women with early preterm labor: Association with spontaneous preterm birth, intra-amniotic inflammation, and microbial invasion of the amniotic cavity

PROBLEM

We aimed to determine whether altered levels of various extracellular matrix (ECM)-related and serine protease proteins in the amniotic fluid (AF) are associated with imminent spontaneous preterm birth (SPTB; ≤7 days) and intra-amniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) in women with early preterm labor (PTL).

METHOD OF STUDY

This retrospective cohort study included 252 women with singleton pregnancies undergoing transabdominal amniocentesis who demonstrated PTL (24-31 weeks). The AF was cultured for microorganism detection to characterize MIAC. IL-6 concentrations were determined in the AF samples to identify IAI (≥2.6 ng/mL). The following mediators were measured in the AF samples using ELISA: kallistatin, lumican, MMP-2, SPARC, TGFBI, and uPA.

RESULTS

Kallistatin, MMP-2, TGFBI, and uPA levels were significantly higher and SPARC and lumican levels were significantly lower in the AF of women who spontaneously delivered within 7 days than in the AF of those who delivered after 7 days; the levels of the first five mediators were independent of baseline clinical variables. In the multivariate analysis, elevated levels of kallistatin, MMP-2, TGFBI, and uPA and low levels of lumican and SPARC in the AF were significantly associated with IAI/MIAC and MIAC, even after adjusting for the gestational age at sampling. The areas under the curves of the aforementioned biomarkers ranged from 0.58 to 0.87 for the diagnoses of each of the corresponding endpoints.

CONCLUSION

ECM-related (SPARC, TGFBI, lumican, and MMP-2) and serine protease (kallistatin and uPA) proteins in the AF are involved in preterm parturition and regulation of intra-amniotic inflammatory/infectious responses in PTL.

Noninvasive prediction models of intra-amniotic infection in women with preterm labor

BACKGROUND

Among women with preterm labor, those with intra-amniotic infection present the highest risk of early delivery and the most adverse outcomes. The identification of intra-amniotic infection requires amniocentesis, perceived as too invasive by women and physicians. Noninvasive methods for identifying intra-amniotic infection and/or early delivery are crucial to focus early efforts on high-risk preterm labor women while avoiding unnecessary interventions in low-risk preterm labor women.

OBJECTIVE

This study modeled the best performing models, integrating biochemical data with clinical and ultrasound information to predict a composite outcome of intra-amniotic infection and/or spontaneous delivery within 7 days.

STUDY DESIGN

From 2015 to 2020, data from a cohort of women, who underwent amniocentesis to rule in or rule out intra-amniotic infection or inflammation, admitted with a diagnosis of preterm labor at <34 weeks of gestation at the Hospital Clinic and Hospital Sant Joan de Déu, Barcelona, Spain, were used. At admission, transvaginal ultrasound was performed, and maternal blood and vaginal samples were collected. Using high-dimensional biology, vaginal proteins (using multiplex immunoassay), amino acids (using high-performance liquid chromatography), and bacteria (using 16S ribosomal RNA gene amplicon sequencing) were explored to predict the composite outcome. We selected ultrasound, maternal blood, and vaginal predictors that could be tested with rapid diagnostic techniques and developed prediction models employing machine learning that was applied in a validation cohort.

RESULTS

A cohort of 288 women with preterm labor at <34 weeks of gestation, of which 103 (35%) had a composite outcome of intra-amniotic infection and/or spontaneous delivery within 7 days, were included in this study. The sample was divided into derivation (n=116) and validation (n=172) cohorts. Of note, 4 prediction models were proposed, including ultrasound transvaginal cervical length, maternal C-reactive protein, vaginal interleukin 6 (using an automated immunoanalyzer), vaginal pH (using a pH meter), vaginal lactic acid (using a reflectometer), and vaginal Lactobacillus genus (using quantitative polymerase chain reaction), with areas under the receiving operating characteristic curve ranging from 82.2% (95% confidence interval, ±3.1%) to 85.2% (95% confidence interval, ±3.1%), sensitivities ranging from 76.1% to 85.9%, and specificities ranging from 75.2% to 85.1%.

CONCLUSION

The study results have provided proof of principle of how noninvasive methods suitable for point-of-care systems can select high-risk cases among women with preterm labor and might substantially aid in clinical management and outcomes while improving the use of resources and patient experience.

Cervical microRNA expression and spontaneous preterm birth

BACKGROUND

Preterm birth remains a major public health issue affecting 10% of all pregnancies and increases risks of neonatal morbidity and mortality. Approximately 50% to 60% of preterm births are spontaneous, resulting from preterm premature rupture of membranes or preterm labor. The pathogenesis of spontaneous preterm birth is incompletely understood, and prediction of preterm birth remains elusive. Accurate prediction of preterm birth would reduce infant morbidity and mortality through targeted patient referral to hospitals equipped to care for preterm infants. Two previous studies have analyzed cervical microRNAs in association with spontaneous preterm birth and the length of gestation, but the extent to which microRNAs serve as predictive biomarkers remains unknown.

OBJECTIVE

This study aimed to examine associations between cervical microRNA expression and spontaneous preterm birth, with the specific goal of identifying a subset of microRNAs that predict spontaneous preterm birth.

STUDY DESIGN

We performed a prospective, nested, case-control study of 25 cases with spontaneous preterm birth and 49 term controls. Controls were matched to cases in a 2:1 ratio on the basis of age, parity, and self-identified race. Cervical swabs were collected at a mean gestational age of 17.1 (4.8) weeks of gestation, and microRNAs were analyzed using a quantitative polymerase chain reaction array. Normalized microRNA expression was compared between cases and controls, and a false discovery rate of 0.2 was applied to account for multiple comparisons. Histopathologic analysis of slides of cervical swab samples was performed to quantify leukocyte burden for adjustment in conditional regression models. We explored the use of Relief-based unsupervised identification of top microRNAs and support vector machines to predict spontaneous preterm birth. We performed microRNA enrichment analysis to explore potential biologic targets and pathways in which up-regulated microRNAs might be involved.

RESULTS

Of the 754 microRNAs on the polymerase chain reaction array, 346 were detected in ≥75% of participants' cervical swabs. Average cervical microRNA expression was significantly higher in cases of spontaneous preterm birth than in controls (P=.01). There were 95 significantly up-regulated individual microRNAs (>2-fold change) in cases of subsequent spontaneous preterm birth compared with term controls (P<.05; q<0.2). Notably, miR-143, miR-30e-3p, and miR-199b were all significantly up-regulated, which is consistent with the 1 previous study of cervical microRNA and spontaneous preterm birth. A Relief-based, novel variable (feature) selection machine learning approach had low-to-moderate prediction accuracy, with an area under the receiver operating curve of 0.71. Enrichment analysis revealed that identified microRNAs may modulate inflammatory cell signaling.

CONCLUSION

In this prospective nested case-control study of cervical microRNA expression and spontaneous preterm birth, we identified a global increase in microRNA expression and up-regulation of 95 distinct microRNAs in association with subsequent spontaneous preterm birth. Larger and more diverse studies are required to determine the ability of microRNAs to accurately predict spontaneous preterm birth, and mechanistic work to facilitate development of novel therapeutic interventions to prevent spontaneous preterm birth is warranted.

Cervicovaginal Cytokines to Predict the Onset of Normal and Preterm Labor: a Pseudo-longitudinal Study

Inflammatory processes associated with human parturition are still not completely understood, not only because the gap between inflammation and the onset of labor has been difficult to study but also because of the limited knowledge about the role of cervicovaginal fluid (CVF) cytokines during the sequence of labor. We aimed to determine whether CVF cytokines could predict the onset of normal and preterm labor. Chemokines and proinflammatory and anti-inflammatory cytokines in CVF were measured in a pseudo-longitudinal manner in healthy women between 12 and 41 weeks gestation with intact fetal membranes before and during the first stage of labor. Women were grouped into five stages, from the absence of uterine activity and cervical changes to regular uterine contractions with cervix dilation > 3 cm (active phase of labor). Of 144 women with spontaneous labor, 96 gave birth at term, 48 gave birth preterm, and both groups displayed similar cytokine concentrations. We found positive correlations between proinflammatory cytokines and the initial sequence of labor, using individual cytokines and score-based data by principal component analysis (IFN-γ, TNF-α, IL-1β, IL-6) as dependent variables. The risk of labor onset increased as the concentrations of IL-6 increased (hazard ratio = 202.09, 95% confidence interval = 24.57-1662.49, P < 0.001). The IL-6 concentration predicted the onset of labor within 12 days of sampling (area under the time-dependent ROC curve = 0.785, 95% confidence interval = 0.693-0.877). Here, we showed that regardless of gestational age, the onset of labor could be predicted by the IL-6 concentration in the CVF, since the initial sequence of spontaneous labor displayed an inflammatory response expressed by the increase in proinflammatory cytokines.

Breaking Down the Barrier: The Role of Cervical Infection and Inflammation in Preterm Birth

Approximately 40% of cases of spontaneous preterm birth (sPTB) are associated with ascending intrauterine infections. The cervix serves as a physical and immunological gatekeeper, preventing the ascent of microorganisms from the vagina to the amniotic cavity. The cervix undergoes remodeling during pregnancy. It remains firm and closed from the start until the late third trimester of pregnancy and then dilates and effaces to accommodate the passage of the fetus during delivery. Remodeling proceeds appropriately and timely to maintain the pregnancy until term delivery. However, risk factors, such as acute and chronic infection and local inflammation in the cervix, may compromise cervical integrity and result in premature remodeling, predisposing to sPTB. Previous clinical studies have established bacterial (i.e., chlamydia, gonorrhea, mycoplasma, etc.) and viral infections (i.e., herpesviruses and human papillomaviruses) as risk factors of PTB. However, the exact mechanism leading to PTB is still unknown. This review focuses on: (1) the epidemiology of cervical infections in pregnant patients; (2) cellular mechanisms that may explain the association of cervical infections to premature cervical ripening and PTB; (3) endogenous defense mechanisms of the cervix that protect the uterine cavity from infection and inflammation; and (4) potential inflammatory biomarkers associated with cervical infection that can serve as prognostic markers for premature cervical ripening and PTB. This review will provide mechanistic insights on cervical functions to assist in managing cervical infections during pregnancy.

The Role of Innate Immune System in the Human Amniotic Membrane and Human Amniotic Fluid in Protection Against Intra-Amniotic Infections and Inflammation

Intra-amniotic infection and inflammation (IAI) affect fetal development and are highly associated with preterm labor and premature rupture of membranes, which often lead to adverse neonatal outcomes. Human amniotic membrane (hAM), the inner part of the amnio-chorionic membrane, protects the embryo/fetus from environmental dangers, including microbial infection. However, weakened amnio-chorionic membrane may be breached or pathogens may enter through a different route, leading to IAI. The hAM and human amniotic fluid (hAF) respond by activation of all components of the innate immune system. This includes changes in 1) hAM structure, 2) presence of immune cells, 3) pattern recognition receptors, 4) cytokines, 5) antimicrobial peptides, 6) lipid derivatives, and 7) complement system. Herein we provide a comprehensive and integrative review of the current understanding of the innate immune response in the hAM and hAF, which will aid in design of novel studies that may lead to breakthroughs in how we perceive the IAI.

Elevated inflammatory mediators from the maternal-fetal interface to fetal circulation during labor

BACKGROUND

Elevated cytokines, like IL-1βand IL-6, are known to contribute to the pathogenesis of labor. However, the change of inflammatory mediators in maternal-fetal interface to fetal circulation is obscure.

STUDY DESIGN AND METHODS

We investigated the changes of inflammatory cytokines, chemokines and macrophage in maternal-fetal interface tissues and fetal circulation of women in labor vs. non-labor. Human myometrium, placenta, decidua, fetal membrane and umbilical blood were obtained from in-labor and non-in-labor women who eventually delivered live, singleton infants at term (>37 weeks gestation) by elective caesarean section. Luminex was used to measure the level of cytokines (TNF-α, IL-1β, IL-6, IL-8) and chemokines (MCP-1, GM-CSF, MIP-1α, MIP-1β) in each sample (tissue and umbilical blood). Macrophage infiltration was demonstrated by immunohistochemistry.

RESULTS

During labor, the level of cytokines TNF-α, IL-1β, IL-6 and IL-8 and chemokine MCP-1 and MIP-1β in myometrium is significantly higher (p < 0.05), than those obtained from non-laboring patients. This increase coincides with the influx of macrophage into the myometrium. In addition, IL-1β and IL-8 (p < 0.05) are also up regulated in fetal membrane during labor compared to non-labor. The cytokines do not change significantly in placenta and decidua tissue. In fetal circulation, IL-6 (p < 0.05) is up regulated in umbilical vein blood in labor group. IL-8 (p = 0.08) in umbilical vein also show an increasing trend during labor.

CONCLUSIONS

There are markedly elevated inflammatory mediators in maternal-fetal interface during labor. The increased maternal inflammatory factors released into the fetal circulation through placenta circulation at the time of labor. This increase coincides with the influx of macrophage into the pregnancy tissue, suggesting that the inflammatory response might play an important role in the onset of labor.