Placental inflammation

Comprehensive assessment of placental inflammation: Novel approach in predicting retinopathy of prematurity

The purpose of this study was to determine the independent association between placental inflammation and the development of retinopathy of prematurity (ROP). This retrospective cohort study included 591 neonates born with a gestational age (GA) ≤32 weeks and/or a birthweight (BW) ≤1500 g. Clinical data were retrospectively collected, and placentas were reexamined for acute (e.g. chorioamnionitis and funisitis) and chronic placental inflammation (e.g. chorioamnionitis, villitis of unknown etiology and chronic deciduitis). Severe acute chorioamnionitis was defined as the presence of confluent polymorphonuclear leukocytes or subchorionic microabscesses. Outcomes explored were GA, BW, small for gestational age (SGA), mechanical ventilation duration, postnatal corticosteroids, sepsis, necrotizing enterocolitis, and ROP. Acute histological chorioamnionitis and funisitis were associated with lower GA, lower SGA rates, increased duration of mechanical ventilation and increased ROP rates, while chronic chorioamnionitis and villitis were associated with higher GA and increased SGA rates. BW was significantly lower in neonates with chronic deciduitis. Subanalysis of placentas without maternal and fetal vascular malperfusion also showed increased rates of severe acute chorioamnionitis (42 % vs. 21 %), funisitis (61 % vs. 35 %) in neonates with ROP. Multivariable regression analysis revealed two placental inflammatory factors to be independently associated with ROP: severe acute chorioamnionitis (OR 2.1; 95 % CI 1.1-3.8) and funisitis (OR 1.7; 95 % CI 1.0-2.9). Structured placental evaluation of the presence of severe acute chorioamnionitis and funisitis is valuable in predicting the development of ROP. This increased risk of ROP development could be integrated into the neonatal treatment approach of high-risk neonates in a very early stage in order to reduce ROP.

Deep learning for fetal inflammatory response diagnosis in the umbilical cord

INTRODUCTION

Inflammation of the umbilical cord can be seen as a result of ascending intrauterine infection or other inflammatory stimuli. Acute fetal inflammatory response (FIR) is characterized by infiltration of the umbilical cord by fetal neutrophils, and can be associated with neonatal sepsis or fetal inflammatory response syndrome. Recent advances in deep learning in digital pathology have demonstrated favorable performance across a wide range of clinical tasks, such as diagnosis and prognosis. In this study we classified FIR from whole slide images (WSI).

METHODS

We digitized 4100 histological slides of umbilical cord stained with hematoxylin and eosin (H&E) and extracted placental diagnoses from the electronic health record. We build models using attention-based whole slide learning models. We compared strategies between features extracted by a model (ConvNeXtXLarge) pretrained on non-medical images (ImageNet), and one pretrained using histopathology images (UNI). We trained multiple iterations of each model and combined them into an ensemble.

RESULTS

The predictions from the ensemble of models trained using UNI achieved an overall balanced accuracy of 0.836 on the test dataset. In comparison, the ensembled predictions using ConvNeXtXLarge had a lower balanced accuracy of 0.7209. Heatmaps generated from top accuracy model appropriately highlighted arteritis in cases of FIR 2. In FIR 1, the highest performing model assigned high attention to areas of activated-appearing stroma in Wharton's Jelly. However, other high-performing models assigned attention to umbilical vessels.

DISCUSSION

We developed models for diagnosis of FIR from placental histology images, helping reduce interobserver variability among pathologists. Future work may examine the utility of these models for identifying infants at risk of systemic inflammatory response or early onset neonatal sepsis.

Utero-placental (vascular) development throughout pregnancy in women with polycystic ovary syndrome: the Rotterdam Periconceptional Cohort

Objective

To study utero-placental vascular development from the first trimester onward in pregnant women with polycystic ovary syndrome (PCOS) and successful live births, compared with pregnant women without PCOS, after in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment or natural conception.

Design

Prospective periconceptional cohort study in a single tertiary hospital.

Subjects

Participants with ongoing pregnancies with available serial three-dimensional ultrasound scans were divided into 3 groups: women with PCOS; subfertile group, pregnancies who conceived via IVF/ICSI without PCOS; and fertile group, pregnancies who conceived naturally without PCOS.

Exposure

PCOS diagnosis.

Main Outcome Measures

During the first-trimester, placental volume (PV) and utero-placental vascular volume (uPVV) were measured offline in three-dimensional ultrasound volumes obtained at 7, 9, and 11 weeks' gestational age (GA) using Virtual Organ Analysis and Virtual Reality. Serial measurements were obtained from uterine artery pulsatility and resistance indices (UtA PI and UtA RI) measured by pulsed-wave Doppler ultrasound as well as mean arterial pressure at 7, 9, 11, 13, 22, and 32 weeks' GA. Similarly, the umbilical artery PI and RI were measured at 22 and 32 weeks' GA.

Results

We included 206 pregnancies in our study (PCOS n = 41; subfertile n = 63; fertile n = 102). Significantly negative associations were observed between PCOS and placental measurements (PV, uPVV, and their ratio) at 11 weeks' GA with both the subfertile and fertile group as reference (e.g., uPVV 11 weeks' GA: betaPCOS-fertile -0.18 ∛cm3 [95% confidence interval: -0.30; -0.06]). UtA PI and RI were significantly lower throughout pregnancy in women with PCOS compared with the subfertile and fertile group. Women with PCOS showed a negative association with umbilical artery PI and RI at 32 weeks' GA compared with the subfertile and fertile group as reference.

Conclusion

Women with PCOS show decreased first-trimester placental development at 11 weeks' GA compared with pregnancies without PCOS in the subfertile and fertile group. Additionally, these women also display lower UtA PI and UtA RI compared with women without PCOS. These results support the hypothesis that PCOS impacts early placental development, potentially contributing to adverse pregnancy outcomes. Further research should focus on the underlying pathophysiology and the modifying role of IVF/ICSI treatment.

Placental histopathology in early-onset fetal growth restriction with use of sildenafil, a secondary analysis of the Dutch STRIDER study

OBJECTIVES

Placental pathology lesions are common in early-onset fetal growth restriction (eoFGR). Therapeutic interventions to improve eoFGR outcomes are needed. In the international STRIDER trials (Sildenafil Therapy In Dismal prognosis Early-onset intrauterine growth Restriction) sildenafil didn't improve perinatal outcomes of eoFGR. We aimed to study the underlying placental pathology in the Dutch STRIDER trial and the effects of sildenafil on placental histopathology by describing the associations with sildenafil treatment, placental-dysfunction serum biomarkers and markers of oxidative stress.

METHODS

The Dutch STRIDER trial was a randomized controlled trial of sildenafil versus placebo in 216 singleton pregnancies complicated by eoFGR, included between 20+0- and 29+6-weeks' gestation. In 158 cases, placental histology was available. Lesions were classified independently by three perinatal pathologists blinded for clinical data, according to the international criteria of the Amsterdam Placental Workshop Group Consensus Statement. Blood samples taken at inclusion were analyzed for free thiols (FT), placental growth factor (PlGF) and soluble FMS-like tyrosine kinase-1 (sFlt-1, n = 85).

RESULTS

The 'big four' placental lesions (maternal and fetal vascular malperfusion, and chronic or acute inflammatory lesions) were equally distributed in both groups. However, massive perivillous fibrin deposition (MPFD) and chronic histiocytic intervillositis (CHIV) were less common in the sildenafil-treated group compared to the placebo-treated group (p = 0.026 and p = 0.043). FT, PlGF and sFlt-1 at inclusion were not discriminative for placental lesions.

CONCLUSIONS

Sildenafil had no effect on common placental lesions. The lower incidence of MPFD and CHIV after sildenafil exposure merits more research on the interaction between sildenafil and the immune system.

Chronic Inflammation Offers Hints About Viable Therapeutic Targets for Preeclampsia and Potentially Related Offspring Sequelae

The combination of hypertension with systemic inflammation during pregnancy is a hallmark of preeclampsia, but both processes also convey dynamic information about its antecedents and correlates (e.g., fetal growth restriction) and potentially related offspring sequelae. Causal inferences are further complicated by the increasingly frequent overlap of preeclampsia, fetal growth restriction, and multiple indicators of acute and chronic inflammation, with decreased gestational length and its correlates (e.g., social vulnerability). This complexity prompted our group to summarize information from mechanistic studies, integrated with key clinical evidence, to discuss the possibility that sustained or intermittent systemic inflammation-related phenomena offer hints about viable therapeutic targets, not only for the prevention of preeclampsia, but also the neurobehavioral and other developmental deficits that appear to be overrepresented in surviving offspring. Importantly, we feel that carefully designed hypothesis-driven observational studies are necessary if we are to translate the mechanistic evidence into child health benefits, namely because multiple pregnancy disorders might contribute to heightened risks of neuroinflammation, arrested brain development, or dysconnectivity in survivors who exhibit developmental problems later in life.

Prenatal chronic inflammation and children's executive function development

Fetal inflammation, typically measured indirectly through prenatal maternal cytokine markers, has been shown to impact early childhood executive functions (EFs), which are central to later cognitive and life outcomes. Here, we assessed the impact of prenatal inflammation on EF developmental trajectories using direct placenta histopathology measures in 131 mothers who predominantly self-identified as Black (90.8% Black; 0.8% Asian American, 1.5% biracial, 0.8% Latinx, 3.1% White, 3.1% Missing). We found that placental measures of inflammation were associated with limited gain in EF development from 3 to 5 years old. In follow up analyses, we addressed whether screening questionnaires in infancy might aid in classification of infants as higher risk for subsequent EF problems. We found that parent responses to the Ages & Stages Questionnaire and the Infant/Toddler Sensory Profile at 12 months predict the development of EF abilities in children exposed to chronic inflammation. These findings open promising opportunities for early screening of children at risk for poor executive functioning in children exposed to prenatal inflammation.

Impacts of heat exposure in utero on long-term health and social outcomes: a systematic review

BACKGROUND

Climate change, particularly global warming, is amongst the greatest threats to human health. While short-term effects of heat exposure in pregnancy, such as preterm birth, are well documented, long-term effects have received less attention. This review aims to systematically assess evidence on the long-term impacts on the foetus of heat exposure in utero.

METHODS

A search was conducted in August 2019 and updated in April 2023 in MEDLINE(PubMed). We included studies on the relationship of environmental heat exposure during pregnancy and any long-term outcomes. Risk of bias was assessed using tools developed by the Joanna-Briggs Institute, and the evidence was appraised using the GRADE approach. Synthesis without Meta-Analysis (SWiM) guidelines were used.

RESULTS

Eighteen thousand six hundred twenty one records were screened, with 29 studies included across six outcome groups. Studies were mostly conducted in high-income countries (n = 16/25), in cooler climates. All studies were observational, with 17 cohort, 5 case-control and 8 cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals ranged in age from neonates to adults, and the elderly. Increasing heat exposure during pregnancy was associated with decreased earnings and lower educational attainment (n = 4/6), as well as worsened cardiovascular (n = 3/6), respiratory (n = 3/3), psychiatric (n = 7/12) and anthropometric (n = 2/2) outcomes, possibly culminating in increased overall mortality (n = 2/3). The effect on female infants was greater than on males in 8 of 9 studies differentiating by sex. The quality of evidence was low in respiratory and longevity outcome groups to very low in all others.

CONCLUSIONS

Increasing heat exposure was associated with a multitude of detrimental outcomes across diverse body systems. The biological pathways involved are yet to be elucidated, but could include epigenetic and developmental perturbations, through interactions with the placenta and inflammation. This highlights the need for further research into the long-term effects of heat exposure, biological pathways, and possible adaptation strategies in studies, particularly in neglected regions. Heat exposure in-utero has the potential to compound existing health and social inequalities. Poor study design of the included studies constrains the conclusions of this review, with heterogenous exposure measures and outcomes rendering comparisons across contexts/studies difficult.

TRIAL REGISTRATION

PROSPERO CRD 42019140136.

Clinical chorioamnionitis at term: definition, pathogenesis, microbiology, diagnosis, and treatment

Clinical chorioamnionitis, the most common infection-related diagnosis in labor and delivery units, is an antecedent of puerperal infection and neonatal sepsis. The condition is suspected when intrapartum fever is associated with two other maternal and fetal signs of local or systemic inflammation (eg, maternal tachycardia, uterine tenderness, maternal leukocytosis, malodorous vaginal discharge or amniotic fluid, and fetal tachycardia). Clinical chorioamnionitis is a syndrome caused by intraamniotic infection, sterile intraamniotic inflammation (inflammation without bacteria), or systemic maternal inflammation induced by epidural analgesia. In cases of uncertainty, a definitive diagnosis can be made by analyzing amniotic fluid with methods to detect bacteria (Gram stain, culture, or microbial nucleic acid) and inflammation (white blood cell count, glucose concentration, interleukin-6, interleukin-8, matrix metalloproteinase-8). The most common microorganisms are Ureaplasma species, and polymicrobial infections occur in 70% of cases. The fetal attack rate is low, and the rate of positive neonatal blood cultures ranges between 0.2% and 4%. Intrapartum antibiotic administration is the standard treatment to reduce neonatal sepsis. Treatment with ampicillin and gentamicin have been recommended by professional societies, although other antibiotic regimens, eg, cephalosporins, have been used. Given the importance of Ureaplasma species as a cause of intraamniotic infection, consideration needs to be given to the administration of antimicrobial agents effective against these microorganisms such as azithromycin or clarithromycin. We have used the combination of ceftriaxone, clarithromycin, and metronidazole, which has been shown to eradicate intraamniotic infection with microbiologic studies. Routine testing of neonates born to affected mothers for genital mycoplasmas could improve the detection of neonatal sepsis. Clinical chorioamnionitis is associated with decreased uterine activity, failure to progress in labor, and postpartum hemorrhage; however, clinical chorioamnionitis by itself is not an indication for cesarean delivery. Oxytocin is often administered for labor augmentation, and it is prudent to have uterotonic agents at hand to manage postpartum hemorrhage. Infants born to mothers with clinical chorioamnionitis near term are at risk for early-onset neonatal sepsis and for long-term disability such as cerebral palsy. A frontier is the noninvasive assessment of amniotic fluid to diagnose intraamniotic inflammation with a transcervical amniotic fluid collector and a rapid bedside test for IL-8 for patients with ruptured membranes. This approach promises to improve diagnostic accuracy and to provide a basis for antimicrobial administration.

Placental characteristics and neonatal weights among women with malaria-preeclampsia comorbidity and healthy pregnancies

BACKGROUND

Malaria and preeclampsia are leading causes of maternal morbidity and mortality in sub-Saharan Africa. They contribute significantly to poor perinatal outcomes like low neonatal weight by causing considerable placental morphological changes that impair placental function. Previous studies have described the effects of either condition on the placental structure but the structure of the placenta in malaria-preeclampsia comorbidity is largely understudied despite its high burden. This study aimed to compare the placental characteristics and neonatal weights among women with malaria-preeclampsia comorbidity versus those with healthy pregnancies.

METHODOLOGY

We conducted a retrospective cohort study among 24 women with malaria-preeclampsia comorbidity and 24 women with healthy pregnancies at a County Hospital in Western Kenya. Neonatal weights, gross and histo-morphometric placental characteristics were compared among the two groups.

RESULTS

There was a significant reduction in neonatal weights (P<0.001), placental weights (P = 0.028), cord length (P<0.001), and cord diameter (P<0.001) among women with malaria-preeclampsia comorbidity compared to those with healthy pregnancies. There was also a significant reduction in villous maturity (P = 0.016) and villous volume density (P = 0.012) with increased villous vascularity (P<0.007) among women with malaria-preeclampsia comorbidity compared to those with healthy pregnancies.

CONCLUSION

Placental villous maturity and villous volume density are significantly reduced in patients with malaria-preeclampsia comorbidity with a compensatory increase in villous vascularity. This leads to impaired placental function that contributes to lower neonatal weights.

Analysis of the microbiome in maternal, intrauterine and fetal environments based on 16S rRNA genes following different durations of membrane rupture

The incidence of chorioamnionitis and neonatal sepsis increases with the increasing time of rupture of membranes. Changes in the amount and categories of microbiomes in maternal and fetal environments after membrane rupture have yet to be discussed. In order to determine the microbiome diversity and signature in the maternal, intrauterine, and fetal environments of different durations following membrane rupture, we collected samples of fetal membrane, amniotic fluid, cord blood and maternal peripheral blood from singleton pregnant women and divided them into five groups according to the duration of membrane rupture. DNA was isolated from the samples, and the V3V4 region of bacterial 16S rRNA genes was sequenced. We found that the alpha diversity of the fetal membrane microbiome increased significantly 12 h after membrane rupture, while the beta diversity of the amniotic fluid microbiome increased 24 h after membrane rupture. In cord blood, the mean proportion of Methylobacterium and Halomonadaceae reached the highest 12 h after membrane rupture, and the mean proportion of Prevotella reached the highest 24 h after membrane rupture. The LEfSe algorithm showed that Ruminococcus, Paludibaculum, Lachnospiraceae, and Prevotella were detected earlier in cord blood or maternal blood and then detected in fetal membranes or amniotic fluid, which may suggest a reverse infection model. In conclusion, the microbes may invade the placenta 12 h after membrane rupture and invaded the amniotic cavity 24 h after membrane rupture. In addition to the common ascending pattern of infection, the hematogenous pathway of intrauterine infection should also be considered among people with rupture of membranes.

Smoking during pregnancy is associated with the placental proteome

Maternal smoking during pregnancy (MSDP) is a significant risk factor for the development of foetal, neonatal, and childhood morbidities. We hypothesized that infants exposed to MSDP have a distinct proteomic expression in their term placentas compared to infants without such an exposure. A total of 39 infants exposed (cord blood cotinine levels of >1 ng/mL) and 44 infants not exposed to MSDP were included in the study. Women with chronic disease, body mass index of > 30, or a history of uterine surgery were excluded. Total proteome abundance was analysed with quantitative mass spectrometry. For univariate analysis of differences in placental protein levels between groups, ANOVA with multiple testing corrections by the Benjamini-Hochberg method was used. For multivariate analysis, we used principal component analysis, partial least squares, lasso, random forest, and neural networks. The univariate analyses showed four differentially abundant proteins (PXDN, CYP1A1, GPR183, and KRT81) when heavy and moderate smoking groups were compared to non-smokers. With the help of machine learning, we found that an additional six proteins (SEPTIN3, CRAT, NAAA, CD248, CADM3, and ZNF648) were discriminants of MSDP. The placental abundance of these ten proteins together explained 74.1% of the variation in cord blood cotinine levels (p = 0.002). Infants exposed to MSDP showed differential abundance of proteins in term placentas. We report differential placental abundance of several proteins for the first time in the setting of MSDP. We believe that these findings supplement the current understanding of how MSDP affects the placental proteome.

Assisted reproductive technology (ART) and epigenetic modifications in the placenta

Assisted reproductive technology (ART) has become common amongst couples with infertility issues. ART is known to be successful, but epidemiological data indicates that ART is associated with placental disorders. Additionally, reports show increased risks of short- and long-term complications in children born to mothers undergoing ART. However, the mechanisms responsible for these events are obscure. The placenta is considered as a key organ for programming of diseases and ART procedures are suggested to alter the placental function and intrauterine growth trajectories. Epigenetic changes in maternal and foetal tissues are suggested to be the underlying mechanisms for these outcomes. Epigenetic regulation is known to evolve following fertilisation and before implantation and subsequently across gestation. During these critical periods of epigenetic 'programming', DNA methylation and chromatin remodelling influence the placental structure and function by regulating the expression of various genes. ART treatment coinciding with epigenetic 'programming' events during gametogenesis and early embryo development may alter the programming phases leading to long-term consequences. Thus, disruptions in placental development observed in ART pregnancies could be associated with altered epigenetic regulation of vital genes in the placenta. The review summarises available literature on the influence of ART procedures on epigenetic changes in the placenta.

Placental pathology is necessary to understand common pregnancy complications and achieve an improved taxonomy of obstetrical disease

The importance of a fully functioning placenta for a good pregnancy outcome is unquestioned. Loss of function can lead to pregnancy complications and is often detected by a thorough placental pathologic examination. Placental pathology has advanced the science and practice of obstetrics and neonatal-perinatal medicine by classifying diseases according to underlying biology and specific patterns of injury. Many past obstacles have limited the incorporation of placental findings into both clinical studies and day-to-day practice. Limitations have included variability in the nomenclature used to describe placental lesions, a shortage of perinatal pathologists fully competent to analyze placental specimens, and a troubling lack of understanding of placental diagnoses by clinicians. However, the potential use of placental pathology for phenotypic classification, improved understanding of the biology of adverse pregnancy outcomes, the development of treatment and prevention, and patient counseling has never been greater. This review, written partly in response to a recent critique published in a major obstetrics-gynecology journal, reexamines the role of placental pathology by reviewing current concepts of biology; explaining the most recent terminology; emphasizing the usefulness of specific diagnoses for obstetrician-gynecologists, neonatologists, and patients; previewing upcoming changes in recommendations for placental submission; and suggesting future improvements. These improvements should include further consideration of overall healthcare costs, cost-effectiveness, the clinical value added of placental assessment, improvements in placental pathology education and practice, and leveraging of placental pathology to identify new biomarkers of disease and evaluate novel therapies tailored to specific clinicopathologic phenotypes of both women and infants.

Perinatal Cerebral Ischemic Lesion and SARS-CoV-2 Infection during Pregnancy: A Case Report and a Review of the Literature

Perinatal stroke is related to possible differences in predisposing factors and outcomes between acutely and retrospectively diagnosed cases. In most cases, there are different risk factors and infections that could play an important role. Thus far, different clinical manifestations have been reported in children presenting with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), ranging from asymptomatic status to severe disease sustained by an immune-mediated inflammatory response. SARS-CoV-2 has been associated with severe neurological diseases including seizures and encephalitis in both adults and children. However, there are still few reports regarding the possible relation between SARS-CoV-2 infection of mothers during pregnancy and the neurologic outcome of the newborns. We described the case of a newborn diagnosed with a perinatal stroke, born at 35 weeks of gestation from a mother presenting with SARS- CoV-2 infection during the last months of pregnancy. We also added a brief review of the literature with similar cases. Close monitoring and early intervention in young children born to infected mothers would be highly recommended for the potential neurodevelopmental risk.

Congenital Herpes Simplex Virus: A Histopathological View of the Placenta

Congenital Herpes simplex virus (HSV) infection is considered a common pregnancy pathology that is not always easy to diagnose. This study aimed to present the spectrum of placental histopathological lesions in pregnancies complicated by HSV infection. MEDLINE and Google Scholar databases were searched using the keywords "HSV" and "placental histopathology" up to June 20, 2022. Study inclusion required presenting placental histopathological anomalies in pregnant women diagnosed with HSV infection antenatally, during labor, or postnatally. Herein, we briefly present placental pathogenesis conditions, which have been correlated with congenital HSV infection, providing clinicians with a short review describing herpetic placental pathology.

The correlation between placental histology and microbiologic infection in the diagnosis of chorioamnionitis in preterm delivery

INTRODUCTION

This study sought to investigate the correlation between histologically proven chorioamnionitis and placental bacteriologic infection in preterm births.

METHODS

Women who gave birth before 34 + 0 weeks' gestation at a tertiary medical center between the years 2018-2019 were identified by a database review. Data was collected on clinical characteristics and findings on placental histology, cultures, and polymerase chain reaction. The correlation between histologically confirmed chorioamnionitis and bacteriologic infection was evaluated.

RESULTS

Of 183 placentas included in the study, 88 (48.1%) were histologically positive for chorioamnionitis and 95 (51.9%) were negative. Baseline characteristics were similar in the patients with and without chorioamnionitis. Concordance rates between the histology and microbiology results in the two groups were 51.1% and 64.2%, respectively. Similar types of bacterial microorganisms were isolated in both groups, though at different rates. On chi-square analysis of association, a positive microbiological study had a sensitivity of 51.1%, specificity of 64.2%, and positive predictive value of 56.9% for predicting histologically confirmed chorioamnionitis. Histologically confirmed chorioamnionitis was associated with higher antepartum white blood cell count (14.2 ± 4.6 vs 12.3 ± 3.3 K/μL; p = 0.01), higher rate of clinically suspected chorioamnionitis (10.2% vs 1.1%, p = 0.02), and higher rate of neonatal adverse composite outcome (36.4% vs. 22.1%, p = 0.009).

DISCUSSION

The correlation between histologic and bacteriologic placental findings in the setting of early premature delivery is not high, nor is the clinical yield of placental bacteriology. The discordant results might be explained by early stage of bacterial infection, hard-to-cultivate bacterial species, noninfectious conditions, or contamination of the placental surfaces during passage through the vaginal tract.

Value of Placental Examination in the Diagnostic Evaluation of Stillbirth

ObjectiveThe aim was to assess the contribution of placental examination in the etiologic investigation of stillbirth. Materials and Methods: A retrospective review of stillbirths that occurred after 14 weeks gestation was conducted for a one-year period. Twin pregnancies and fetuses without placentas were excluded. According to the fetoplacental examination, stillbirths were classified into etiologic groups. Results: A total of 147 stillbirths were selected. They were associated with placental, materno-fetal, fetal and multiple causes in 89 cases (61%), 23 cases (16%), 14 cases (9%) and 13 cases (9%), respectively. Unexplained stillbirths were observed in 8 cases (5%). Placental abnormalities were identified in 132/147 cases (90%). They were consistent with vascular, inflammatory and developmental lesions in 82/132 cases (61%), 28/132 cases (21%) and 18/132 cases (13%), respectively. Conclusion: Placental lesions were the main causes of stillbirth and were predominantly of vascular type including chronic villous hypoxia-ischemia and funicular anomalies.

Diffuse and Localized SARS-CoV-2 Placentitis: Prevalence and Pathogenesis of an Uncommon Complication of COVID-19 Infection During Pregnancy

Coronavirus disease 2019 (COVID-19) infection in pregnancy has been associated with preterm delivery and preeclampsia. A less frequent and underrecognized complication is extensive placental infection which is associated with high rates of perinatal morbidity and mortality. The frequency, early pathogenesis, and range of lesions associated with this infection are poorly understood. We conducted a population-based study of placental pathology from all mothers with COVID-19 (n=271) over an 18-month period delivering within our health system. The overall prevalence of diffuse severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) placentitis, as defined by typical histology and immunohistochemical (IHC) staining for SARS-CoV-2 spike protein, was 14.8/1000, but increased to 59/1000 in preterm births. We also identified 3 cases with isolated small foci of localized SARS-CoV-2 placentitis, characterized by focal perivillous fibrin and intervillositis, which illustrate the early pathogenesis and suggest that infection may be contained in some cases. Two other placental lesions were more common in mothers with COVID-19, high-grade maternal vascular malperfusion in preterm deliveries and high-grade chronic villitis at term (5/5 cases tested of the latter were negative by IHC for SARS-CoV-2). Additional investigation of diffuse and localized SARS-CoV-2 placentitis by IHC showed loss of BCL-2, C4d staining in surrounding villi, and an early neutrophil-predominant intervillous infiltrate that later became dominated by monocyte-macrophages. We propose a model of focal infection of syncytiotrophoblast by virally infected maternal leukocytes leading to loss of BCL-2 and apoptosis. Infection is then either contained by surrounding fibrinoid (localized) or initiates waves of aponecrosis and immune activation that spread throughout the villous parenchyma (diffuse).

Downregulation of transcriptional activity, increased inflammation, and damage in the placenta following in utero Zika virus infection is associated with adverse pregnancy outcomes

Zika virus (ZIKV) infection during pregnancy causes serious adverse outcomes to the developing fetus, including fetal loss and birth defects known as congenital Zika syndrome (CZS). The mechanism by which ZIKV infection causes these adverse outcomes and specifically, the interplay between the maternal immune response and ZIKV replication has yet to be fully elucidated. Using an immunocompetent mouse model of transplacental ZIKV transmission and adverse pregnancy outcomes, we have previously shown that Asian lineage ZIKV disrupts placental morphology and induces elevated secretion of IL-1β. In the current manuscript, we characterized placental damage and inflammation during in utero African lineage ZIKV infection. Within 48 hours after ZIKV infection at embryonic day 10, viral RNA was detected in placentas and fetuses from ZIKA infected dams, which corresponded with placental damage and reduced fetal viability as compared with mock infected dams. Dams infected with ZIKV had reduced proportions of trophoblasts and endothelial cells and disrupted placental morphology compared to mock infected dams. While placental IL-1β was increased in the placenta, but not the spleen, within 3 hours post infection, this was not caused by activation of the NLRP3 inflammasome. Using bulk mRNAseq from placentas of ZIKV and mock infected dams, ZIKV infection caused profound downregulation of the transcriptional activity of genes that may underly tissue morphology, neurological development, metabolism, cell signaling and inflammation, illustrating that in utero ZIKV infections causes disruption of pathways associated with CZS in our model.

Pathologist interobserver variability in diagnosing acute ascending intrauterine infection

The histologic diagnosis of acute ascending intrauterine infection permits a higher-efficacy identification of both subclinical infection and clinical chorioamnionitis, but procedures for placental pathology need to adopt a unified approach and work toward reproducible grading and staging systems. We conducted a retrospective chart review of 696 placental records from single and multiple deliveries between January 2011 and February 2020. Then, we compared original diagnoses with diagnoses based on Redline criteria, which is an internationally recognized system of staging and grading. Of the 696 cases available for review, 255 had complete medical records. Findings showed a strong degree of agreement (90%-100%) between original investigators' histological diagnoses of acute ascending intrauterine infection and a review by researchers using Redline criteria. Although interobserver agreement was good, more education is needed on Redline criteria to avoid missed cases (primarily Stage 1), support protocols for pathologists and obstetricians/gynecologists in determining which cases need to be investigated, and the development of reporting standards for acute ascending intrauterine infection and feedback mechanisms during follow-up.

Microfluidic Organs-on-a-Chip for Modeling Human Infectious Diseases

Infectious diseases present tremendous challenges to human progress and public health. The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the associated coronavirus disease 2019 (COVID-19) pandemic continue to pose an imminent threat to humanity. These infectious diseases highlight the importance of developing innovative strategies to study disease pathogenesis and protect human health. Although conventional in vitro cell culture and animal models are useful in facilitating the development of effective therapeutics for infectious diseases, models that can accurately reflect human physiology and human-relevant responses to pathogens are still lacking. Microfluidic organs-on-a-chip (organ chips) are engineered microfluidic cell culture devices lined with living cells, which can resemble organ-level physiology with high fidelity by rebuilding tissue-tissue interfaces, mechanical cues, fluidic flow, and the biochemical cellular microenvironment. They present a unique opportunity to bridge the gap between in vitro experimental models and in vivo human pathophysiology and are thus a promising platform for disease studies and drug testing. In this Account, we first introduce how recent progress in organ chips has enabled the recreation of complex pathophysiological features of human infections in vitro. Next, we describe the progress made by our group in adopting organ chips and other microphysiological systems for the study of infectious diseases, including SARS-CoV-2 viral infections and intrauterine bacterial infections. Respiratory symptoms dominate the clinical manifestations of many COVID-19 patients, even involving the systemic injury of many distinct organs, such as the lung, the gastrointestinal tract, and so forth. We thus particularly highlight our recent efforts to explore how lung-on-a-chip and intestine-on-a-chip might be useful in addressing the ongoing viral pandemic of COVID-19 caused by SARS-CoV-2. These organ chips offer a potential platform for studying virus-host interactions and human-relevant responses as well as accelerating the development of effective therapeutics against COVID-19. Finally, we discuss opportunities and challenges in the development of next-generation organ chips, which are urgently needed for developing effective and affordable therapies to combat infectious diseases. We hope that this Account will promote awareness about in vitro organ microphysiological systems for modeling infections and stimulate joint efforts across multiple disciplines to understand emerging and re-emerging pandemic diseases and rapidly identify innovative interventions.

Maternal omega-3 fatty acids maintained positive maternal lipids and cytokines profile, and improved pregnancy outcomes of C57BL/6 mice

Omega (n)-3 polyunsaturated fatty acids (PUFA) are known to regulate lipid metabolism and inflammation; however, the regulation of maternal lipid metabolism and cytokines profile by n-3 PUFA during different gestation stages, and its impact on fetal sustainability is not known. We investigated the effects of maternal diet varying in n-3 PUFA prior to, and during gestation, on maternal metabolic profile, placental inflammatory cytokines, and fetal outcomes. Female C57BL/6 mice were fed either a high, low or very low (9, 3 or 1% w/w n-3 PUFA) diet, containing n-6:n-3 PUFA of 5:1, 20:1 and 40:1, respectively for two weeks before mating, and throughout pregnancy. Animals were sacrificed prior to mating (NP), and during pregnancy at gestation days 6.5, 12.5 and 18.5. Maternal metabolic profile, placental cytokines and fetal outcomes were determined. Our results show for the first time that a maternal diet high in n-3 PUFA prevented dyslipidemia in NP mice, and maintained the expected lipid profile during pregnancy. However, females fed the very low n-3 PUFA diet became hyperlipidemic prior to pregnancy, and carried this profile into pregnancy. Maternal diet high in n-3 PUFA maintained maternal plasma progesterone and placental pro-inflammatory cytokines profile, and sustained fetal numbers throughout pregnancy, while females fed the low and very-low n-3 PUFA diet had fewer fetuses. Our findings demonstrate the importance of maternal diet before, and during pregnancy, to maintain maternal metabolic profile and fetus sustainability. These findings are important when designing dietary strategies to optimize maternal metabolism during pregnancy for successful pregnancy outcome.

Amniotic fluid interleukin 6 and interleukin 8 are superior predictors of fetal lung injury compared with maternal or fetal plasma cytokines or placental histopathology in a nonhuman primate model

BACKGROUND

Intra-amniotic infection or inflammation is common in early preterm birth and associated with substantial neonatal lung morbidity owing to fetal exposure to proinflammatory cytokines and infectious organisms. Amniotic fluid interleukin 8, a proinflammatory cytokine, was previously correlated with the development of neonatal bronchopulmonary dysplasia, but whether amniotic fluid cytokines or placental pathology more accurately predicts neonatal lung pathology and morbidity is unknown. We have used a pregnant nonhuman primate model of group B Streptococcus infection to study the pathogenesis of intra-amniotic infection, bacterial invasion of the amniotic cavity and fetus, and microbial-host interactions. In this nonhuman primate model, we have studied the pathogenesis of group B Streptococcus strains with differing potential for virulence, which has resulted in a spectrum of intra-amniotic infection and fetal lung injury that affords the opportunity to study the inflammatory predictors of fetal lung pathology and injury.

OBJECTIVE

This study aimed to determine whether fetal lung injury is best predicted by placental histopathology or the cytokine response in amniotic fluid or maternal plasma.

STUDY DESIGN

Chronically catheterized pregnant monkeys (Macaca nemestrina, pigtail macaque) at 116 to 125 days gestation (term at 172 days) received a choriodecidual inoculation of saline (n=5), weakly hemolytic group B Streptococcus strain (n=5, low virulence), or hyperhemolytic group B Streptococcus strain (n=5, high virulence). Adverse pregnancy outcomes were defined as either preterm labor, microbial invasion of the amniotic cavity, or development of the fetal inflammatory response syndrome. Amniotic fluid and maternal and fetal plasma samples were collected after inoculation, and proinflammatory cytokines (tumor necrosis factor alpha, interleukin beta, interleukin 6, interleukin 8) were measured by a multiplex assay. Cesarean delivery was performed at the time of preterm labor or within 1 week of inoculation. Fetal necropsy was performed at the time of delivery. Placental pathology was scored in a blinded fashion by a pediatric pathologist, and fetal lung injury was determined by a semiquantitative score from histopathology evaluating inflammatory infiltrate, necrosis, tissue thickening, or collapse scored by a veterinary pathologist.

RESULTS

The principal findings in our study are as follows: (1) adverse pregnancy outcomes occurred more frequently in animals receiving hyperhemolytic group B Streptococcus (80% with preterm labor, 80% with fetal inflammatory response syndrome) than in animals receiving weakly hemolytic group B Streptococcus (40% with preterm labor, 20% with fetal inflammatory response syndrome) and in controls (0% preterm labor, 0% fetal inflammatory response syndrome); (2) despite differences in the rate of adverse pregnancy outcomes and fetal inflammatory response syndrome, fetal lung injury scores were similar between animals receiving the weakly hemolytic group B Streptococcus strains and animals receiving the hyperhemolytic group B Streptococcus strains; (3) fetal lung injury score was significantly correlated with peak amniotic fluid cytokines interleukin 6 and interleukin 8 but not tumor necrosis factor alpha or interleukin 1 beta; and (4) fetal lung scores were poorly correlated with maternal and fetal plasma cytokine levels and placental pathology.

CONCLUSION

Amniotic fluid interleukin 6 and interleukin 8 levels were superior predictors of fetal lung injury than placental histopathology or maternal plasma cytokines. This evidence supports a role for amniocentesis in the prediction of neonatal lung morbidity owing to intra-amniotic infection, which cannot be provided by cytokine analysis of maternal plasma or placental histopathology.

Organ-on-a-chip technology for the study of the female reproductive system

Over the past decade, organs-on-a-chip and microphysiological systems have emerged as a disruptive in vitro technology for biopharmaceutical applications. By enabling new capabilities to engineer physiological living tissues and organ units in the precisely controlled environment of microfabricated devices, these systems offer great promise to advance the frontiers of basic and translational research in biomedical sciences. Here, we review an emerging body of interdisciplinary work directed towards harnessing the power of organ-on-a-chip technology for reproductive biology and medicine. The focus of this topical review is to provide an overview of recent progress in the development of microengineered female reproductive organ models with relevance to drug delivery and discovery. We introduce the engineering design of these advanced in vitro systems and examine their applications in the study of pregnancy, infertility, and reproductive diseases. We also present two case studies that use organ-on-a-chip design principles to model placental drug transport and hormonally regulated crosstalk between multiple female reproductive organs. Finally, we discuss challenges and opportunities for the advancement of reproductive organ-on-a-chip technology.

Four major patterns of placental injury: a stepwise guide for understanding and implementing the 2016 Amsterdam consensus

The Amsterdam classification system defines four major patterns of placental injury, maternal vascular malperfusion, fetal vascular malperfusion, acute chorioamnionitis, and villitis of unknown etiology, and lists the histologic findings that characterize each. However, there continues to be uncertainty regarding specific definitions, histologic mimics, grading and staging, and what combination of findings is required to diagnose each pattern of injury in a reproducible fashion. The purpose of this review is to clarify some of these issues by suggesting a stepwise approach to more fully realize the potential of this new classification system. In our view, the critical steps for correctly identifying and communicating each pattern of injury are (1) familiarity with the underlying pathophysiology and known clinical associations, (2) incorporation of important gross findings, (3) learning to recognize underlying architectural alterations and defining features at low power, (4) using higher magnification to narrow the differential diagnosis and assess severity (grading) and duration (staging), and (5) adopting a template for generating standardized placental reports that succinctly provide useful information for patient care and research applications.

RNA Sequencing Reveals Distinct Immune Responses in the Chorioamniotic Membranes of Women with Preterm Labor and Microbial or Sterile Intra-amniotic Inflammation

Preterm labor precedes premature birth, the leading cause of neonatal morbidity and mortality worldwide. Preterm labor can occur in the context of either microbe-associated intra-amniotic inflammation (i.e., intra-amniotic infection) or intra-amniotic inflammation in the absence of detectable microorganisms (i.e., sterile intra-amniotic inflammation). Both intra-amniotic infection and sterile intra-amniotic inflammation trigger local immune responses that have deleterious effects on fetal life. Yet, the extent of such immune responses in the fetal tissues surrounding the amniotic cavity (i.e., the chorioamniotic membranes) is poorly understood. By using RNA sequencing (RNA seq) as a discovery approach, we found that there were significant transcriptomic differences involving host response to pathogens in the chorioamniotic membranes of women with intra-amniotic infection compared to those from women without inflammation. In addition, the sterile or microbial nature of intra-amniotic inflammation was associated with distinct transcriptomic profiles in the chorioamniotic membranes. Moreover, the immune response in the chorioamniotic membranes of women with sterile intra-amniotic inflammation was milder in nature than that induced by microbes and involved the upregulation of alarmins and inflammasome-related molecules. Lastly, the presence of maternal and fetal inflammatory responses in the placenta was associated with the upregulation of immune processes in the chorioamniotic membranes. Collectively, these findings provide insight into the immune responses against microbes or alarmins that take place in the fetal tissues surrounding the amniotic cavity, shedding light on the immunobiology of preterm labor and birth.

COVID-19 and Pregnancy: Vertical Transmission and Inflammation Impact on Newborns

The COVID-19 pandemic is ongoing and we are still compiling new findings to decipher and understand SARS-CoV-2 infection during pregnancy. No reports encompass any conclusive confirmation of vertical transmission. Nevertheless, cases of fetal distress and multiple organ failure have been reported, as well as rare cases of fetal demise. While clinicians and scientists continue to seek proof of vertical transmission, they miss the greater point, namely the cause of preterm delivery. In this review, we suggest that the cause might not be due to the viral infection but the fetal exposure to maternal inflammation or cytokine storm that translates into a complication of COVID-19. This statement is extrapolated from previous experience with infections and inflammation which were reported to be fatal by increasing the risk of preterm delivery and causing abnormal neonatal brain development and resulting in neurological disorders like atypical behavioral phenotype or autistic syndrome. Given the potentially fatal consequences on neonate health, we highlight the urgent need for an animal model to study vertical transmission. The preclinical model will allow us to make the link between SARS-COV-2 infection, inflammation and long-term follow-up of child brain development.

Modeling of Artificial 3D Human Placenta

The placenta is the main organ that allows the fertilized oocyte to develop and mature. It allows the fetus to grow in the prenatal period by transferring oxygen and nutrients between the mother and the fetus. It acts as a basic endocrine organ which creates the physiological changes related to pregnancy and birth in the mother. Removal of wastes and carbon dioxide from the fetus is also achieved by the placenta. It prevents the rejection of the fetus and protects the fetus from harmful effects. Research on the human placenta focuses on understanding the placental structure and function to illuminate the complex structure of this important organ with technological advances. The structure and function of the placental barrier have been investigated with in vitro studies in 2D/3D, and various results have been published comparatively. In this review, we introduce the nature of the placenta with its 3D composition which has been called niche. Different cell types and placental structures are presented. We describe the systems and approaches used in the creation of current 3D placenta, placental transfer models as 3D placental barriers, and micro-engineered 3D placenta on-a-chip to explore complicated placental responses to nanoparticle exposure.

The Prenatal Hormone Milieu in Autism Spectrum Disorder

Though the etiology of autism spectrum disorder (ASD) remains largely unknown, recent findings suggest that hormone dysregulation within the prenatal environment, in conjunction with genetic factors, may alter fetal neurodevelopment. Early emphasis has been placed on the potential role of in utero exposure to androgens, particularly testosterone, to theorize ASD as the manifestation of an "extreme male brain." The relationship between autism risk and obstetric conditions associated with inflammation and steroid dysregulation merits a much broader understanding of the in utero steroid environment and its potential influence on fetal neuroendocrine development. The exploration of hormone dysregulation in the prenatal environment and ASD development builds upon prior research publishing associations with obstetric conditions and ASD risk. The insight gained may be applied to the development of chronic adult metabolic diseases that share prenatal risk factors with ASD. Future research directions will also be discussed.

The pivotal roles of the NOD-like receptors with a PYD domain, NLRPs, in oocytes and early embryo development†

Nucleotide-binding oligomerization domain (NOD)-like receptors with a pyrin domain (PYD), NLRPs, are pattern recognition receptors, well recognized for their important roles in innate immunity and apoptosis. However, several NLRPs have received attention for their new, specialized roles as maternally contributed genes important in reproduction and embryo development. Several NLRPs have been shown to be specifically expressed in oocytes and preimplantation embryos. Interestingly, and in line with divergent functions, NLRP genes reveal a complex evolutionary divergence. The most pronounced difference is the human-specific NLRP7 gene, not identified in rodents. However, mouse models have been extensively used to study maternally contributed NLRPs. The NLRP2 and NLRP5 proteins are components of the subcortical maternal complex (SCMC), which was recently identified as essential for mouse preimplantation development. The SCMC integrates multiple proteins, including KHDC3L, NLRP5, TLE6, OOEP, NLRP2, and PADI6. The NLRP5 (also known as MATER) has been extensively studied. In humans, inactivating variants in specific NLRP genes in the mother are associated with distinct phenotypes in the offspring, such as biparental hydatidiform moles (BiHMs) and preterm birth. Maternal-effect recessive mutations in KHDC3L and NLRP5 (and NLRP7) are associated with reduced reproductive outcomes, BiHM, and broad multilocus imprinting perturbations. The precise mechanisms of NLRPs are unknown, but research strongly indicates their pivotal roles in the establishment of genomic imprints and post-zygotic methylation maintenance, among other processes. Challenges for the future include translations of findings from the mouse model into human contexts and implementation in therapies and clinical fertility management.

Inhibition of the NLRP3 inflammasome can prevent sterile intra-amniotic inflammation, preterm labor/birth, and adverse neonatal outcomes†

Sterile intra-amniotic inflammation is commonly observed in patients with spontaneous preterm labor, a syndrome that commonly precedes preterm birth, the leading cause of perinatal morbidity and mortality worldwide. However, the mechanisms leading to sterile intra-amniotic inflammation are poorly understood and no treatment exists for this clinical condition. Herein, we investigated whether the alarmin S100B could induce sterile intra-amniotic inflammation by activating the NLRP3 inflammasome, and whether the inhibition of this pathway could prevent preterm labor/birth and adverse neonatal outcomes. We found that the ultrasound-guided intra-amniotic administration of S100B induced a 50% rate of preterm labor/birth and a high rate of neonatal mortality (59.7%) without altering the fetal and placental weights. Using a multiplex cytokine array and immunoblotting, we reported that S100B caused a proinflammatory response in the amniotic cavity and induced the activation of the NLRP3 inflammasome in the fetal membranes, indicated by the upregulation of the NLRP3 protein and increased release of active caspase-1 and mature IL-1β. Inhibition of the NLRP3 inflammasome via the specific inhibitor MCC950 prevented preterm labor/birth by 35.7% and reduced neonatal mortality by 26.7%. Yet, inhibition of the NLRP3 inflammasome at term did not drastically obstruct the physiological process of parturition. In conclusion, the data presented herein indicate that the alarmin S100B can induce sterile intra-amniotic inflammation, preterm labor/birth, and adverse neonatal outcomes by activating the NLRP3 inflammasome, which can be prevented by inhibiting such a pathway. These findings provide evidence that sterile intra-amniotic inflammation could be treated by targeting the NLRP3 inflammasome.

Zinc Oxide Exerts Anti-Inflammatory Properties on Human Placental Cells

Background: An aberrant and persistent inflammatory state at the fetal-maternal interface is considered as a key contributor in compromised pregnancies. Decidual endothelial cells (DECs) play a pivotal role in the control of the local decidual inflammation. The aim of the current study was to determine whether dietary supplement with zinc oxide (ZnO), due to its very low adverse effects, may be useful for modulating the inflammatory response in the first trimester of pregnancy. Methods: The anti-inflammatory properties of ZnO in pregnancy were evaluated by in vitro tests on endothelial cells isolated from normal deciduas and on a trophoblast cell line (HTR8/Svneo). The effects of this treatment were analyzed in terms of adhesion molecule expression and inflammatory cytokine secretion, by real time-quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). Results: Our data showed that ZnO was able to reduce the inflammatory response of DECs, in terms of vascular cell adhesion molecule-1 (VCAM-1), interleukin (IL)-8, IL-6, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) expression induced by TNF-α stimulation. This compound exerted no effect on intracellular adhesion molecule-1 (ICAM-1) exocytosis induced by TNF-α on stimulated trophoblast cells, but significantly reduced their IL-6 expression. Conclusion: According to these results, it can be suggested that the ZnO supplement, through its modulation of the pro-inflammatory response of DECs, can be used in pregnancy for the prevention of local decidual inflammation.

Probiotic Enterococcus faecalis Symbioflor 1 ameliorates pathobiont-induced miscarriage through bacterial antagonism and Th1-Th2 modulation in pregnant mice

The bacterium-bacterium interaction between pathogenic and probiotic Enterococcus as well as the bacterium-host interaction between Enterococcus and intestinal epithelium has drawn increasing attentions, but the influence of those interactions on host pregnancy remains largely unexplored. In the present study, we evaluated the effects of probiotic E. faecalis Symbioflor 1 or/and pathogenic E. faecalis OG1RF on the miscarriage of pregnant mice. Using in vitro assays of competition and exclusion and displacement, antagonistic property of E. faecalis Symbioflor 1 against E. faecalis OG1RF was observed, and the former inhibited the translocation of the later in vivo. The rate of miscarriage induced by E. faecalis OG1RF challenge was significantly reduced by 28% with E. faecalis Symbioflor 1 intervention; and the tissue integrity of ileum, colon, uterus, and placenta and placental blood cell density in pregnant mice were drastically improved by such probiotic intervention. Compared with the controls, probiotic intervention significantly upregulated the level of IL-10 and TGF-β, downregulated levels of IFN-γ, and increased progesterone level that reversed the trend of being Th1 predominance state reported for adverse pregnancy outcome at early pregnancy stage. In conclusion, E. faecalis Symbioflor 1 decreased the translocation of E. faecalis OG1RF, prevented pathogen-induced tissue damage, and changed Th1-Th2 homeostasis toward Th2 predominance during early pregnancy resulting in decreased miscarriage. KEY POINTS: •The mechanism of how probiotic E. faecalis Symbioflor 1 improves pregnancy of mice • Influence of interactions of pathogenic and probiotic Enterococcus on host pregnancy • E. faecalis Symbioflor 1 change Th1-Th2 homeostasis toward Th2 predominance.

Villitis of unknown etiology (VUE): effect on placental size and association with clinical parameters

Objectives: Villitis of unknown etiology (VUE) is an inflammatory placental lesion with immune-mediated pathogenesis, diagnosed by histopathological examination. It is one of the three placental lesions which tend to recur in subsequent pregnancies, the other two being chronic histiocytic intervillositis and massive fibrin deposition. The frequency of VUE and its association with maternal, obstetric and neonatal complications are variability reported in the literature. The aim of this study is to determine the frequency of VUE in the population studied and to observe the association of specific subtypes of villitis with clinical features, placental morphometric and microscopic parameters.Methods: Placentas where villitis was observed, were obtained from the pathology database from January 2013 to June 2018. VUE was graded as low grade (LG), high grade (HG) and basal villitis (BV) and subcategorized based on extent and cell type. Its association with selected maternal, neonatal and placental parameters was evaluated.Results: A total of 1603 placentas were received and 163 singleton placentas with villitis (10%) were reported. LG and HG villitis was observed in 58% and 25% cases respectively. Basal villitis was seen in 24% and pure basal villitis without involvement of parenchymal villi was seen in 16.6%. While there was near equal distribution of focal (n = 45) and multifocal (n = 50) LG villitis, diffuse HG villitis (n = 32) was more common than patchy HG villitis (n = 9). Overall villitis was more common in preterm pregnancies (59.5%) with most of them being basal villitis and low-grade villitis (64.2%, p value .029). None of the other maternal and neonatal parameters had any significance. Placental dimensions (length and breadth) showed a significant negative association with VUE, especially high-grade and multifocal low-grade villitis.Conclusion: VUE was a common finding in preterm births and its novel association with placental size opens avenues for further research on alternative mechanisms involved in the association between villitis, placental function and adverse pregnancy outcomes.

Gasdermin D: Evidence of pyroptosis in spontaneous preterm labor with sterile intra-amniotic inflammation or intra-amniotic infection

PROBLEM

Pyroptosis, inflammatory programmed cell death, is initiated through the inflammasome and relies on the pore-forming actions of the effector molecule gasdermin D. Herein, we investigated whether gasdermin D is detectable in women with spontaneous preterm labor and sterile intra-amniotic inflammation or intra-amniotic infection.

METHOD OF STUDY

Amniotic fluid samples (n = 124) from women with spontaneous preterm labor were subdivided into the following groups: (a) those who delivered at term (n = 32); and those who delivered preterm (b) without intra-amniotic inflammation (n = 41), (c) with sterile intra-amniotic inflammation (n = 32), or (d) with intra-amniotic infection (n = 19), based on amniotic fluid IL-6 concentrations and the microbiological status of amniotic fluid (culture and PCR/ESI-MS). Gasdermin D concentrations were measured using an ELISA kit. Multiplex immunofluorescence staining was also performed to determine the expression of gasdermin D, caspase-1, and interleukin-1β in the chorioamniotic membranes. Flow cytometry was used to detect pyroptosis (active caspase-1) in decidual cells from women with preterm labor and birth.

RESULTS

(a) Gasdermin D was detected in the amniotic fluid and chorioamniotic membranes from women who underwent spontaneous preterm labor/birth with either sterile intra-amniotic inflammation or intra-amniotic infection, but was rarely detected in those without intra-amniotic inflammation. (b) Amniotic fluid concentrations of gasdermin D were higher in women with intra-amniotic infection than in those with sterile intra-amniotic inflammation, and its expression in the chorioamniotic membranes was associated with caspase-1 and IL-1β (inflammasome mediators). (c) Decidual stromal cells and leukocytes isolated from women with preterm labor and birth are capable of undergoing pyroptosis given their expression of active caspase-1.

CONCLUSION

Pyroptosis can occur in the context of sterile intra-amniotic inflammation and intra-amniotic infection in patients with spontaneous preterm labor and birth.

Protective effect of metformin on a rat model of lipopolysaccharide-induced preeclampsia

Recent in vitro and clinical studies have found that metformin (MET) may play a preventive or therapeutic role in preeclampsia (PE) and may be a candidate drug for the prevention and/or treatment of PE. In this study, we used lipopolysaccharide (LPS) to induce a PE-like rat model and investigated the intervention effect of MET from the perspectives of clinical manifestations, placental morphology, serum marker for placental injury, systemic inflammatory response and oxidative/nitrative stress, and placental nuclear factor-κB (NF-κB) signaling. The results showed that MET improved LPS-induced hypertension, proteinuria, fetal growth restriction (FGR) and stillbirth, alleviated placental injury and decreased maternal serum marker alpha-fetoprotein (MS-AFP) level; MET suppressed LPS-induced TNF-α and IL-6 productions, reduced oxidative/nitrative stress as evidenced by increased superoxide dismutase (SOD) activity, decreased inducible nitric oxide synthase (iNOS) activity, and decreased levels of malondialdehyde (MDA) and nitric oxide (NO); MET inhibited LPS-induced NF-κB activation in placentas. Based on these findings, it can be concluded that MET is beneficial to the PE-like rat model by protecting placentas from injury, suppressing systemic inflammatory response and oxidative/nitrative stress, and inhibiting placental NF-κB signaling pathway. MET is a promising drug for prevention and/or treatment of PE.

Placental and intra-amniotic inflammation are associated with altered fetal immune responses at birth

INTRODUCTION

High-grade placental inflammation is associated with preterm birth and poor neonatal outcomes. Recent reports suggest that low-grade placental inflammation is common in uncomplicated pregnancies. The relationship between placental inflammation and innate immune anti-microbial responses is unknown. In this study we sought to identify any association between placental inflammation and fetal immune responses.

METHODS

Cord blood samples collected from late preterm and full-term Caesarean section deliveries (n = 44) were exposed to various immune challenges (resiquimod, LPS, PGN, poly (I:C), cGAMP, and 5'ppp-dsRNA) and production of inflammatory mediators (G-CSF, IFN-γ, IL-1β, IL-6, IL-8, IL-10, and TNF-α) was measured by multiplex assay. Hospital histology reports were used to assess the extent of inflammation in the placenta.

RESULTS

Almost half (47.7%) of placentae examined here showed histological evidence of inflammation. Resiquimod, LPS, and PGN elicited strong inflammatory responses in neonatal cord blood, while poly (I:C), cGAMP, and 5'ppp-dsRNA elicited weaker responses. Fetuses with evidence of chorioamnionitis and fetal inflammatory reaction in their placentae had significantly increased immune responses to cGAMP and 5'ppp-dsRNA (ligands for STING and RIG-I, respectively) and significantly decreased immune responses to poly (I:C) (a TLR3 agonist). Interestingly, STING, RIG-I, and TLR3 are all involved in viral response pathways, suggesting that fetuses exposed to chorioamnionitis or fetal inflammatory reaction might respond differently to viruses postnatally.

CONCLUSION

Our data suggest that low-level placental inflammation is associated with altered innate cytokine responses at birth.

Placental inflammation, lifestyle, maternal and early child sensitisation to allergens - the assessment of lifestyle and allergic disease during infancy birth cohort

AIM

To investigate (i) whether maternal sensitisation to allergens, and lifestyle can influence the risk of acute and chronic inflammation of the placenta, in the forms of chorioamnionitis and villitis, respectively, and (ii) whether these placental inflammations are associated with the outcome of sensitisation for the child during preschool age.

METHODS

Placentas from term uncomplicated pregnancies (n = 275) in the assessment of lifestyle and allergic disease during infancy study were analysed for the presence of acute chorioamnionitis and chronic villitis. Stepwise logistic regression was performed to estimate the relative risk of placental inflammation in relation to maternal allergic sensitisation and lifestyle, and the association between placental inflammation and sensitisation of the child up to five years of age.

RESULTS

Parity and delivery at home were independently associated with chorioamnionitis, home delivery only with the low grade. Maternal allergic sensitisation was associated with increased risk of villitis in the bivariable model, however, not in the multivariable model. No significant associations were detected between placental inflammation and the outcome of sensitisation to allergens at five years of age.

CONCLUSION

Our data do not support the hypothesis that the increased risk for sensitisation of a child when the mother is allergic is mediated via placental inflammation.

Clinical chorioamnionitis at term IX: in vivo evidence of intra-amniotic inflammasome activation

Background The inflammasome has been implicated in the mechanisms that lead to spontaneous labor at term. However, whether the inflammasome is activated in the amniotic cavity of women with clinical chorioamnionitis at term is unknown. Herein, by measuring extracellular ASC [apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (CARD)], we investigated whether there is in vivo inflammasome activation in amniotic fluid of patients with clinical chorioamnionitis at term with sterile intra-amniotic inflammation and in those with intra-amniotic infection. Methods This was a retrospective cross-sectional study that included amniotic fluid samples collected from 76 women who delivered after spontaneous term labor with diagnosed clinical chorioamnionitis. Intra-amniotic inflammation was defined as an elevated amniotic fluid interleukin (IL)-6 concentration ≥2.6 ng/mL, and intra-amniotic infection was diagnosed by the presence of microbial invasion of the amniotic cavity (MIAC) accompanied by intra-amniotic inflammation. Patients were classified into the following groups: (1) women without intra-amniotic inflammation or infection (n=16); (2) women with MIAC but without intra-amniotic inflammation (n=5); (3) women with sterile intra-amniotic inflammation (n=15); and (4) women with intra-amniotic infection (n=40). As a readout of in vivo inflammasome activation, extracellular ASC was measured in amniotic fluid by enzyme-linked immunosorbent assay. Acute inflammatory responses in the amniotic fluid and placenta were also evaluated. Results In clinical chorioamnionitis at term: (1) amniotic fluid concentrations of ASC (extracellular ASC is indicative of in vivo inflammasome activation) and IL-6 were greater in women with intra-amniotic infection than in those without intra-amniotic inflammation, regardless of the presence of MIAC; (2) amniotic fluid concentrations of ASC and IL-6 were also higher in women with sterile intra-amniotic inflammation than in those without intra-amniotic inflammation, regardless of the presence of MIAC; (3) amniotic fluid concentrations of IL-6, but not ASC, were more elevated in women with intra-amniotic infection than in those with sterile intra-amniotic inflammation; (4) a positive and significant correlation was observed between amniotic fluid concentrations of ASC and IL-6; (5) no differences were observed in amniotic fluid ASC and IL-6 concentrations between women with and without MIAC in the absence of intra-amniotic inflammation; (6) women with intra-amniotic infection had elevated white blood cell counts and reduced glucose levels in amniotic fluid compared to the other three study groups; and (7) women with intra-amniotic infection presented higher frequencies of acute maternal and fetal inflammatory responses in the placenta than those with sterile intra-amniotic inflammation. Conclusion The intra-amniotic inflammatory response, either induced by alarmins or microbes, is characterized by the activation of the inflammasome - as evidenced by elevated amniotic fluid concentrations of extracellular ASC - in women with clinical chorioamnionitis at term. These findings provide insight into the intra-amniotic inflammatory response in women with clinical chorioamnionitis at term.

Pilot study demonstrates that placental histology can provide an additional tool for diagnosing early-onset neonatal sepsis

AIM

We explored whether placental histology could help to diagnose early-onset neonatal sepsis (EONS), guide clinical decision-making 48 hours after birth and reduce antibiotic use.

METHODS

This study comprised 109 infants born at less than 32 weeks of gestation, who were admitted to the neonatal intensive care unit of Isala, Zwolle, The Netherlands, between January 2013 and December 2013. EONS was defined as clinical symptoms plus raised serial C-reactive protein (CRP) >10 mg/L and a positive (proven EONS) or a negative (suspected EONS) blood culture. Placentas were studied for a histological inflammatory response and scored according to Redline's criteria.

RESULTS

A histological inflammatory response was seen in 15/88 (17%) placentas and this occurred significantly more often in infants with a high suspicion of EONS (p < 0.05). No histological inflammatory response was seen if maternal risk factors for EONS were absent, despite a raised CRP level. Based on placental histology, the duration of antibiotic therapy was reduced from more than five days to 48 hours in 20/27 infants (74%).

CONCLUSION

Histological examination of the placenta helped to diagnose EONS and guide clinical decision-making 48 hours after birth and led to a clinically relevant reduction in antibiotic use.

Inflammasome activation during spontaneous preterm labor with intra-amniotic infection or sterile intra-amniotic inflammation

PROBLEM

The inflammasome is implicated in the mechanisms that lead to spontaneous preterm labor (PTL). However, whether there is inflammasome activation in the amniotic cavity of women with PTL and intra-amniotic infection (IAI) or sterile intra-amniotic inflammation (SIAI) is unknown.

METHOD OF STUDY

Amniotic fluid samples were collected from women with PTL who delivered at term (n = 31) or preterm without IAI or SIAI (n = 35), with SIAI (n = 27), or with IAI (n = 17). As a readout of inflammasome activation, extracellular ASC (apoptosis-associated speck-like protein containing a CARD) was measured in amniotic fluid by ELISA and the expression of ASC, caspase-1, and interleukin (IL)-1β was detected in the chorioamniotic membranes by multiplex immunofluorescence. Acute inflammatory responses in amniotic fluid and the placenta were also evaluated.

RESULTS

(a) Amniotic fluid concentrations of ASC and IL-6 were higher in women with PTL and IAI or SIAI than in those who delivered preterm or at term without intra-amniotic inflammation; (b) amniotic fluid concentrations of ASC and IL-6 were lower in women with PTL and SIAI than in those with IAI; (c) there was a significant nonlinear correlation between ASC and IL-6 amniotic fluid concentrations; (d) the expression of inflammasome-related proteins (ASC, caspase-1, and IL-1β) in the chorioamniotic membranes was increased in women with PTL and IAI or SIAI than in those who delivered preterm or at term without intra-amniotic inflammation; (e) inflammasome activation in the chorioamniotic membranes was weaker in women with PTL and SIAI than in those with IAI; (f) women with PTL and IAI had elevated amniotic fluid white blood cell counts compared to those without this clinical condition; and (g) severe acute placental inflammatory lesions were observed in women with PTL and IAI and in a subset of women with PTL and SIAI.

CONCLUSION

Inflammasome activation occurs in the settings of intra-amniotic infection and sterile intra-amniotic inflammation during spontaneous preterm labor.

The frequency and type of placental histologic lesions in term pregnancies with normal outcome

Objective To determine the frequency and type of histopathologic lesions in placentas delivered by women with a normal pregnancy outcome. Methods This retrospective cohort study included placental samples from 944 women with a singleton gestation who delivered at term without obstetrical complications. Placental lesions were classified into the following four categories as defined by the Society for Pediatric Pathology and by our unit: (1) acute placental inflammation, (2) chronic placental inflammation, (3) maternal vascular malperfusion and (4) fetal vascular malperfusion. Results (1) Seventy-eight percent of the placentas had lesions consistent with inflammatory or vascular lesions; (2) acute inflammatory lesions were the most prevalent, observed in 42.3% of the placentas, but only 1.0% of the lesions were severe; (3) acute inflammatory lesions were more common in the placentas of women with labor than in those without labor; (4) chronic inflammatory lesions of the placenta were present in 29.9%; and (5) maternal and fetal vascular lesions of malperfusion were detected in 35.7% and 19.7%, respectively. Two or more lesions with maternal or fetal vascular features consistent with malperfusion (high-burden lesions) were present in 7.4% and 0.7%, respectively. Conclusion Most placentas had lesions consistent with inflammatory or vascular lesions, but severe and/or high-burden lesions were infrequent. Mild placental lesions may be interpreted either as acute changes associated with parturition or as representative of a subclinical pathological process (intra-amniotic infection or sterile intra-amniotic inflammation) that did not affect the clinical course of pregnancy.

Placental Barrier-on-a-Chip: Modeling Placental Inflammatory Responses to Bacterial Infection

Placental inflammation, as a recognized cause of preterm birth and neonatal mortality, displays extensive placental involvement or damage with the presence of organisms. The inflammatory processes are complicated and tightly associated with increased inflammatory cytokine levels and innate immune activation. However, the deep study of the underlying mechanisms was limited by conventional cell and animal models because of great variations in the architecture and function of placenta. Here, we established a microengineered model of human placental barrier on the chip and investigated the associated inflammatory responses to bacterial infection. The multilayered design of the microdevice mimicked the microscopic structure in the fetal-maternal interfaces of human placenta, and the flow resembled the dynamic environment in the mother's body. Escherichia coli (E. coli), one of the predominant organisms found in fetal organs, were applied to the maternal side, modeling acute placental inflammation. The data demonstrated the complex responses including the increased secretion of inflammatory cytokines by trophoblasts and the adhesion of maternal macrophages following bacterial infection. Particularly, transplacental communication was observed between two placental cells, and implied the potential role of trophoblast in fetal inflammatory response syndrome in clinic. These complex responses are of potential significance to placental dysfunctions, even abnormal fetal development and preterm birth. Collectively, placental barrier-on-a-chip microdevice presents a simple platform to explore the complicated inflammatory responses in human placenta, and might help our understanding of the mechanisms underlying reproductive diseases.

Preterm Birth and Small Size for Gestational Age in Singleton, In Vitro Fertilization Births Using Donor Oocytes

We used 2006-2015 US National Assisted Reproductive Technology Surveillance System data to compare preterm birth and fetal growth for liveborn singletons (24-42 weeks' gestation) following in vitro fertilization with donor versus autologous oocytes. Using binary and multinomial logistic regression, we computed adjusted odds ratios and 95% confidence intervals for associations between use of donor oocytes and preterm delivery, being small for gestational age (SGA), and being large for gestational age (LGA), stratified by fresh and thawed embryo status and accounting for maternal characteristics and year of birth. There were 204,855 singleton births from fresh embryo transfers and 106,077 from thawed embryo transfers. Among fresh embryo transfers, donor oocyte births had higher odds of being preterm (adjusted odd ratio (aOR) = 1.32, 95% confidence interval (CI): 1.27, 1.38) or LGA (aOR = 1.27, 95% CI: 1.21, 1.33) but lower odds of being SGA (aOR = 0.81, 95% CI: 0.77, 0.85). Among thawed embryo transfers, donor oocyte births had higher odds of being preterm (aOR = 1.57, 95% CI: 1.48, 1.65) or SGA (aOR = 1.22, 95% CI: 1.14, 1.31) but lower odds of being LGA (aOR = 0.87, 95% CI: 0.82, 0.92). Use of donor oocytes was associated with increased odds of preterm delivery irrespective of embryo status; odds of being SGA were increased for donor versus autologous oocyte births among thawed embryo transfers only.

Fetal-placental crosstalk occurs through fetal cytokine synthesis and placental clearance

BACKGROUND

Cytokines modulate fetal well-being and contribute to parturition. Their origin in fetal blood, whether maternal, placental or fetal, at the time of parturition remains unclear.

OBJECTIVE

To determine fetal and placental contributions to circulating fetal cytokines by measuring umbilical arterial (UmA) and venous (UmV) concentration differences in uncomplicated term pregnancies in the absence and presence of labor.

METHODS

Term uncomplicated pregnancies were assessed: Group 1 were not in labor and delivered by elective cesarean section (n = 20); Group 2 delivered vaginally following uncomplicated pregnancy and labor (n = 30). UmA and UmV blood was collected before delivery of the placenta to measure circulating cytokines. Placental tissue was collected for histology and to determine cytokine contents and localization.

RESULTS

Group 1 UmA and UmV IL-10 concentrations were similar (504 ± 15 and 468 ± 16 pg/ml, respectively; P ≥ 0.1); other cytokines were below level of detection. During labor, IL-10 concentrations increased 15-34%, but placental contents decreased. Group 2 UmA IL-6 and IL-8 concentrations increased (P < 0.001) to 16.7 ± 1.6 and 18.4 ± 4.3 pg/ml, respectively, but were less (P < 0.001) in UmV, 0.29 ± 0.2 and 0.74 ± 0.3 pg/ml, respectively, demonstrating placental clearances ≥97%. This was associated with >6-fold increases in placental IL-6/IL-8 contents (P < 0.001) and chorioamniotic infiltration of activated maternal neutrophils. IL-6 and IL-10 were localized to villous syncytiotrophoblasts.

CONCLUSIONS

In uncomplicated term pregnancies fetal circulating IL-10 is likely of placental origin, whereas IL-6/IL-8 are derived from the fetus, increase during parturition, and circulating levels are modulated by non-saturable placental clearance, revealing a novel pathway for fetal-placental crosstalk and signaling.

Placental pathology predicts infantile physical development during first 18 months in Japanese population: Hamamatsu birth cohort for mothers and children (HBC Study)

The present study aimed to investigate the relationship between placental pathological findings and physiological development during the neonate and infantile periods. Study participants were 258 infants from singleton pregnancies enrolled in the Hamamatsu Birth Cohort for Mothers and Children (HBC Study) whose placentas were stored in our pathological division. They were followed up from birth to 18 months of age. Physiological development (body weight and the ponderal index [PI]) was assessed at 0, 1, 4, 6, 10, 14, and 18 months. Placental blocks were prepared by random sampling and eleven pathological findings were assessed, as follows: 'Accelerated villous maturation', 'Decidual vasculopathy', 'Thrombosis or Intramural fibrin deposition', 'Avascular villi', 'Delayed villous maturation', 'Maternal inflammatory response', 'Fetal inflammatory response', 'Villitis of unknown etiology (VUE)', 'Deciduitis', 'Maternal vascular malperfusion', and 'Fetal vascular malperfusion'. Mixed model analysis with the use of the xtmixed command by the generic statistical software, Stata version 13.1., identified 'Accelerated villous maturation' and 'Maternal vascular malperfusion' as significant predictors of a lower body weight and 'Deciduitis' as a significant predictor of a small PI, throughout the first 18 months of life. In conclusion, the present study is the first to demonstrate that some pathological findings of the placenta are associated with changes in infantile physical development during the initial 18 months of life in the Japanese population.

Spontaneous preterm birth: advances toward the discovery of genetic predisposition

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.