Genetic contributions to preterm birth: implications from epidemiological and genetic association studies

The relationship between active/passive smoking and spontaneous preterm birth: Data from a multicenter study

BACKGROUND

Prematurity is considered to be the leading cause of death in children under 5 years of age, with one child dying every 2 s. Smoking is known to be one of the factors associated with prematurity, with both immediate and late consequences. However, it is difficult to obtain concrete data on the relationship between smoking and spontaneous preterm birth.

OBJECTIVE

The aim of this study was to evaluate the influence of active and passive smoking on spontaneous preterm birth.

METHODS

This was a multicenter, cross-sectional complementary study that included data on preterm births in 20 maternity hospitals in Brazil between 2011 and 2012. The relationship between smoking category (people who smoke [PWS]; people who smoke indirectly [PWSI]; and people who do not smoke [PWDNS]) and sociodemographic characteristics, birth, and neonatal data was assessed. Statistical analysis was performed using frequencies, percentages, the χ2 test, and stepwise comparisons, with a significance level of 5%.

RESULTS

The original study included 5295 pregnant participants and their preterm infants. There were 1491 spontaneous preterm births (SPBs); 1191 preterm rupture of membranes; 1468 therapeutic preterm births; and 1146 term births. The proportion of women who were PWS during pregnancy was 13.5%, and 31.6% were PWSI. Pregnant individuals who smoked and who smoked indirectly had a higher incidence of SPBs (61.2%) compared with PWDNS (48.4%; P < 0.0001); however, multivariate analysis did not confirm causality.

CONCLUSIONS

This study did not confirm that smoking during pregnancy increases the risk of SPB. PWSI also did not have an increased incidence of spontaneous preterm birth or adverse neonatal outcomes.

Recent Advances and Challenges in the Early Diagnosis and Treatment of Preterm Labor

Preterm birth (PTB) is the primary cause of neonatal mortality and long-term disabilities. The unknown mechanism behind PTB makes diagnosis difficult, yet early detection is necessary for controlling and averting related consequences. The primary focus of this work is to provide an overview of the known risk factors associated with preterm labor and the conventional and advanced procedures for early detection of PTB, including multi-omics and artificial intelligence/machine learning (AI/ML)- based approaches. It also discusses the principles of detecting various proteomic biomarkers based on lateral flow immunoassay and microfluidic chips, along with the commercially available point-of-care testing (POCT) devices and associated challenges. After briefing the therapeutic and preventive measures of PTB, this review summarizes with an outlook.

Prevention of spontaneous preterm delivery – an update on where we are today

Spontaneous preterm birth (delivery before 37 completed weeks) is the single most important cause of perinatal morbidity and mortality. The rate is increasing world-wide with a great disparity between low, middle and high income countries. It has been estimated that the cost of neonatal care for preterm babies is more than 4 times that of a term neonate admitted into the neonatal care. Furthermore, there are high costs associated with long-term morbidity in those who survive the neonatal period. Interventions to stop delivery once preterm labor starts are largely ineffective hence the best approach to reducing the rate and consequences is prevention. This is either primary (reducing or minimizing factors associated with preterm birth prior to and during pregnancy) or secondary - identification and amelioration (if possible) of factors in pregnancy that are associated with preterm labor. In the first category are optimizing maternal weight, promoting healthy nutrition, smoking cessation, birth spacing, avoidance of adolescent pregnancies and screening for and controlling various medical disorders as well as infections prior to pregnancy. Strategies in pregnancy, include early booking for prenatal care, screening and managing medical disorders and their complications, and identifying predisposing factors to preterm labor such as shortening of the cervix and timely instituting progesterone prophylaxis or cervical cerclage where appropriate. The use of biomarkers such as oncofetal fibronectin, placental alpha-macroglobulin-1 and IGFBP-1 where cervical screening is not available or to diagnosis PPROM would identify those that require close monitoring and allow the institution of antibiotics especially where infection is considered a predisposing factor. Irrespective of the approach to prevention, timing the administration of corticosteroids and where necessary tocolysis and magnesium sulfate are associated with an improved outcome. The role of genetics, infections and probiotics and how these emerging dimensions help in the diagnosis of preterm birth and consequently prevention are exciting and hopefully may identify sub-populations for targeted strategies.

The impact of cerclage placement on gestational length in women with premature cervical shortening

OBJECTIVES

Cervical insufficiency (CI) is a condition consistent with painless cervical dilatation that can lead to preterm delivery. Cervical cerclage is a procedure in which cervical suture is performed for preventing preterm labor in several indications. Late emergency cerclage is technically more challenging compared to elective cerclage, performed earlier during pregnancy, prior to cervical changes. Pregnancy outcomes with emergency cerclage were found to be improved in previous reports, but there is still inconclusive data. To assess the effectiveness and safety of emergency cerclage vs. conservative management with progesterone and/or bed resting, in preventing preterm birth and improving neonatal outcomes in women with clinically evident cervical insufficiency.

METHODS

This is a retrospective cohort study conducted on all women diagnosed with cervical insufficiency between the 16th and 24th gestational week who met the inclusion criteria, from January 2012 to December 2018. Obstetric and neonatal outcomes: time from diagnosis to delivery, duration of pregnancy, birth weight and Apgar score, were compared between women who underwent cerclage and those who treated conservatively.

RESULTS

Twenty eight women underwent emergency cerclage (cerclage group) and 194 managed with a conservative therapy, progesterone and/or bed rest (control group). Time from diagnosis to delivery 13 weeks vs. 8 weeks and birth weight 2,418 g vs. 1914 g were significantly higher in the first cohort. Average pregnancy duration was three weeks longer in the cerclage group, but that was not significant. No complications occurred in the cerclage group and no difference in mode of delivery were found.

CONCLUSIONS

Emergency cerclage is an effective and safe procedure in preventing preterm birth and prolongation of pregnancy, in women with cervical insufficiency in the late second trimester.

Deleterious and Protective Psychosocial and Stress-Related Factors Predict Risk of Spontaneous Preterm Birth

OBJECTIVES

The aim of the study was to: (1) Identify (early in pregnancy) psychosocial and stress-related factors that predict risk of spontaneous preterm birth (PTB, gestational age <37 weeks); (2) Investigate whether "protective" factors (e.g., happiness/social support) decrease risk; (3) Use the Dhabhar Quick-Assessment Questionnaire for Stress and Psychosocial Factors (DQAQ-SPF) to rapidly quantify harmful or protective factors that predict increased or decreased risk respectively, of PTB.

STUDY DESIGN

This is a prospective cohort study. Relative risk (RR) analyses investigated association between individual factors and PTB. Machine learning-based interdependency analysis (IDPA) identified factor clusters, strength, and direction of association with PTB. A nonlinear model based on support vector machines was built for predicting PTB and identifying factors that most strongly predicted PTB.

RESULTS

Higher levels of deleterious factors were associated with increased RR for PTB: General anxiety (RR = 8.9; 95% confidence interval [CI] = 2.0,39.6), pain (RR = 5.7; CI = 1.7,17.0); tiredness/fatigue (RR = 3.7; CI = 1.09,13.5); perceived risk of birth complications (RR = 4; CI = 1.6,10.01); self-rated health current (RR = 2.6; CI = 1.0,6.7) and previous 3 years (RR = 2.9; CI = 1.1,7.7); and divorce (RR = 2.9; CI = 1.1,7.8). Lower levels of protective factors were also associated with increased RR for PTB: low happiness (RR = 9.1; CI = 1.25,71.5); low support from parents/siblings (RR = 3.5; CI = 0.9,12.9), and father-of-baby (RR = 3; CI = 1.1,9.9). These factors were also components of the clusters identified by the IDPA: perceived risk of birth complications (p < 0.05 after FDR correction), and general anxiety, happiness, tiredness/fatigue, self-rated health, social support, pain, and sleep (p < 0.05 without FDR correction). Supervised analysis of all factors, subject to cross-validation, produced a model highly predictive of PTB (AUROC or area under the receiver operating characteristic = 0.73). Model reduction through forward selection revealed that even a small set of factors (including those identified by RR and IDPA) predicted PTB.

CONCLUSION

These findings represent an important step toward identifying key factors, which can be assessed rapidly before/after conception, to predict risk of PTB, and perhaps other adverse pregnancy outcomes. Quantifying these factors, before, or early in pregnancy, could identify women at risk of delivering preterm, pinpoint mechanisms/targets for intervention, and facilitate the development of interventions to prevent PTB.

KEY POINTS

· Newly designed questionnaire used for rapid quantification of stress and psychosocial factors early during pregnancy.. · Deleterious factors predict increased preterm birth (PTB) risk.. · Protective factors predict decreased PTB risk..

Systematic review of preterm birth multi-omic biomarker studies

Preterm birth (PTB) is one of the leading causes of deaths in infants under the age of five. Known risk factors of PTB include genetic factors, lifestyle choices or infection. Identification of omic biomarkers associated with PTB could aid clinical management of women at high risk of early labour and thereby reduce neonatal morbidity. This systematic literature review aimed to identify and summarise maternal omic and multi-omic (genomics, transcriptomics, proteomics and metabolites) biomarker studies of PTB. Original research articles were retrieved from three databases: PubMed, Web of Science and Science Direct, using specified search terms for each omic discipline. PTB studies investigating genomics, transcriptomics, proteomics or metabolomics biomarkers prior to onset of labour were included. Data were collected and reviewed independently. Pathway analyses were completed on the biomarkers from non-targeted omic studies using Reactome pathway analysis tool. A total of 149 omic studies were identified; most of the literature investigated proteomic biomarkers. Pathway analysis identified several cellular processes associated with the omic biomarkers reported in the literature. Study heterogeneity was observed across the research articles, including the use of different gestation cut-offs to define PTB. Infection/inflammatory biomarkers were identified across majority of papers using a range of targeted and non-targeted approaches.

Study protocol to quantify the genetic architecture of sonographic cervical length and its relationship to spontaneous preterm birth

INTRODUCTION

A short cervix (cervical length <25 mm) in the midtrimester (18-24 weeks) of pregnancy is a powerful predictor of spontaneous preterm delivery. Although the biological mechanisms of cervical change during pregnancy have been the subject of extensive investigation, little is known about whether genes influence the length of the cervix, or the extent to which genetic factors contribute to premature cervical shortening. Defining the genetic architecture of cervical length is foundational to understanding the aetiology of a short cervix and its contribution to an increased risk of spontaneous preterm delivery.

METHODS/ANALYSIS

The proposed study is designed to characterise the genetic architecture of cervical length and its genetic relationship to gestational age at delivery in a large cohort of Black/African American women, who are at an increased risk of developing a short cervix and delivering preterm. Repeated measurements of cervical length will be modelled as a longitudinal growth curve, with parameters estimating the initial length of the cervix at the beginning of pregnancy, and its rate of change over time. Genome-wide complex trait analysis methods will be used to estimate the heritability of cervical length growth parameters and their bivariate genetic correlation with gestational age at delivery. Polygenic risk profiling will assess maternal genetic risk for developing a short cervix and subsequently delivering preterm and evaluate the role of cervical length in mediating the relationship between maternal genetic variation and gestational age at delivery.

ETHICS/DISSEMINATION

The proposed analyses will be conducted using deidentified data from participants in an IRB-approved study of longitudinal cervical length who provided blood samples and written informed consent for their use in future genetic research. These analyses are preregistered with the Center for Open Science using the AsPredicted format and the results and genomic summary statistics will be published in a peer-reviewed journal.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

Protein interaction networks define the genetic architecture of preterm birth

The likely genetic architecture of complex diseases is that subgroups of patients share variants in genes in specific networks sufficient to express a shared phenotype. We combined high throughput sequencing with advanced bioinformatic approaches to identify such subgroups of patients with variants in shared networks. We performed targeted sequencing of patients with 2 or 3 generations of preterm birth on genes, gene sets and haplotype blocks that were highly associated with preterm birth. We analyzed the data using a multi-sample, protein–protein interaction (PPI) tool to identify significant clusters of patients associated with preterm birth. We identified shared protein interaction networks among preterm cases in two statistically significant clusters, p < 0.001. We also found two small control-dominated clusters. We replicated these data on an independent, large birth cohort. Separation testing showed significant similarity scores between the clusters from the two independent cohorts of patients. Canonical pathway analysis of the unique genes defining these clusters demonstrated enrichment in inflammatory signaling pathways, the glucocorticoid receptor, the insulin receptor, EGF and B-cell signaling, These results support a genetic architecture defined by subgroups of patients that share variants in genes in specific networks and pathways which are sufficient to give rise to the disease phenotype.

Risk factors associated with preterm birth: a retrospective study in Mukalla Maternity and Childhood Hospital, Hadhramout Coast/Yemen

Preterm birth (PTB) is a major determinant of neonatal mortality, morbidity and childhood disability. It has long-term adverse consequences for health. The causes of preterm delivery (PTD) are multifactorial. This study was conducted to determine the most common risk factors for PTB at Mukalla Maternity and Childhood (MCH) Hospital, Yemen. A retrospective case-control study was conducted. It involved the records of 100 women with live PTD as cases and 400 women with live term delivery as controls at Mukalla MCH Hospital in 2018. All the data were analysed using the Statistical Package for the Social Sciences (version 24). The statistical relationship between independent variables and PTB was studied by the Chi-square test in bivariate analysis and logistic regression in multivariate analysis. The strength of association was confirmed by using odds ratios (ORs) with a 95% confidence interval (CI). Risk factors with statistically significant association with premature birth were a family history of PTD (adjusted OR [AOR] 2.353; CI 1.3-4.258, p-value 0.005), pre-eclampsia (AOR 4.120; CI 1.818-9.340, p-value 0.001), parity (AOR 2.139; CI 1.249-3.662, p-value 0.006), premature rupture of membranes (AOR 4.161; CI 2.323-7.456, p-value 0.000) and abnormal amniotic fluid volume (AOR 4.534; CI 1.364-15.071, p-value 0.014). An early recognition of preterm risk factors will help medical staff and healthcare workers to identify women with a high-risk pregnancy.

MicroRNAs isolated from peripheral blood in the first trimester predict spontaneous preterm birth

OBJECTIVE

To predict spontaneous preterm birth among pregnant women in an African American population using first trimester peripheral blood maternal immune cell microRNA.

STUDY DESIGN

This was a retrospective nested case-control study in pregnant patients enrolled between March 2006 and October 2016. For initial study inclusion, samples were selected that met the following criteria: 1) singleton pregnancy; 2) maternal body mass index (BMI) <30 kg/m2; 3) blood sample drawn between 6 weeks to 12 weeks 6 days gestation; 4) live born neonate with no detectable birth defects. Using these entry criteria, 486 samples were selected for study inclusion. After sample quality was confirmed, 139 term deliveries (38-42 weeks) and 18 spontaneous preterm deliveries (<35 weeks) were selected for analysis. Samples were divided into training and validation sets. Real time reverse transcription quantitative polymerase chain reaction (rt-qPCR) was performed on each sample for 45 microRNAs. MicroRNA Risk Scores were calculated on the training set and area-under-the-curve receiver-operating-characteristic (AUC-ROC) curves were derived from the validation set.

RESULTS

The AUC-ROC for the validation set delivering preterm was 0.80 (95% CI: 0.69 to 0.88; p = 0.0001), sensitivity 0.89, specificity of 0.71 and a mean gestational age of 10.0 ±1.8 weeks (range: 6.6-12.9 weeks). When the validation population was divided by gestational age at the time of venipuncture into early first trimester (mean 8.4 ±1.0 weeks; range 6.6-9.7 weeks) and late first trimester (mean 11.5±0.8 weeks; range 10.0-12.9 weeks), the AUC-ROC scores for early and late first trimester were 0.79 (95% CI: 0.63 to 0.91) and 0.81 (95% CI: 0.66 to 0.92), respectively.

CONCLUSION

Quantification of first trimester peripheral blood MicroRNA identifies risk of spontaneous preterm birth in samples obtained early and late first trimester of pregnancy in an African American population.

Is association of preterm birth with cognitive-neurophysiological impairments and ADHD symptoms consistent with a causal inference or due to familial confounds?

BACKGROUND

Preterm birth is associated with an increased risk for cognitive-neurophysiological impairments and attention-deficit/hyperactivity disorder (ADHD). Whether the associations are due to the preterm birth insult per se, or due to other risk factors that characterise families with preterm-born children, is largely unknown.

METHODS

We employed a within-sibling comparison design, using cognitive-performance and event-related potential (ERP) measures from 104 preterm-born adolescents and 104 of their term-born siblings. Analyses focused on ADHD symptoms and cognitive and ERP measures from a cued continuous performance test, an arrow flanker task and a reaction time task.

RESULTS

Within-sibling analyses showed that preterm birth was significantly associated with increased ADHD symptoms (β = 0.32, p = 0.01, 95% CI 0.05 to 0.58) and specific cognitive-ERP impairments, such as IQ (β = -0.20, p = 0.02, 95% CI -0.40 to -0.01), preparation-vigilance measures and measures of error processing (ranging from β = 0.71, -0.35). There was a negligible within-sibling association between preterm birth with executive control measures of inhibition (NoGo-P3, β = -0.07, p = 0.45, 95% CI -0.33 to 0.15) or verbal working memory (digit span backward, β = -0.05, p = 0.63, 95% CI -0.30 to 0.18).

CONCLUSIONS

Our results suggest that the relationship between preterm birth with ADHD symptoms and specific cognitive-neurophysiological impairments (IQ, preparation-vigilance and error processing) is independent of family-level risk and consistent with a causal inference. In contrast, our results suggest that previously observed associations between preterm birth with executive control processes of inhibition and working memory are instead linked to background characteristics of families with a preterm-born child rather than preterm birth insult per se. These findings suggest that interventions need to target both preterm-birth specific and family-level risk factors.

Genetic landscape of preterm birth due to cervical insufficiency: Comprehensive gene analysis and patient next-generation sequencing data interpretation

Preterm delivery is both a traumatizing experience for the patient and a burden on the healthcare system. A condition distinguishable by its phenotype in prematurity is cervical insufficiency, where certain cases exhibit a strong genetic component. Despite genomic advancements, little is known about the genetics of human cervix remodeling during pregnancy. Using selected gene approaches, a few studies have demonstrated an association of common gene variants with cervical insufficiency. However, until now, no study has employed comprehensive methods to investigate this important subject matter. In this study, we asked: i) are there genes reliably linked to cervical insufficiency and, if so, what are their roles? and ii) what is the proportion of cases of non-syndromic cervical insufficiency attributable to these genetic variations? We performed next-generation sequencing on 21 patients with a clinical presentation of cervical insufficiency. To assist the sequencing data interpretation, we retrieved all known genes implicated in cervical functioning through a systematic literature analysis and additional gene searches. These genes were then classified according to their relation to the questions being posed by the study. Patients' sequence variants were filtered for pathogenicity and assigned a likelihood of being contributive to phenotype development. Gene extraction and analysis revealed 12 genes primarily linked to cervical insufficiency, the majority of which are known to cause collagenopathies. Ten patients carried disruptive variants potentially contributive to the development of non-syndromic cervical insufficiency. Pathway enrichment analysis of variant genes from our cohort revealed an increased variation burden in genes playing roles in tissue mechanical and biomechanical properties, i.e. collagen biosynthesis and cell-extracellular matrix communications. Consequently, the proposed idea of cervical insufficiency being a subtle form of collagenopathy, now strengthened by our genetic findings, might open up new opportunities for improved patient evaluation and management.

Association of socioeconomic status and clinical and demographic conditions with the prevalence of preterm birth

OBJECTIVE

To examine the effects of socioeconomic and demographic conditions on the prevalence of preterm birth in a local community.

METHODS

Pregnant women (aged ≥16 years) willing to provide informed consent in one of the two languages of the community were recruited in South Africa between August 2007 and January 2015. Specifically designed case report forms collected information and measurements prospectively.

RESULTS

After reviewing the medical records of 5806 women, it was possible to identify those who had spontaneous preterm birth (SPTB), induced preterm birth (IPTB), or spontaneous term birth (STB). Women with IPTB (vs SPTB) were more obese and had higher education levels and household incomes; more had telephones and running water at home. They enrolled earlier and more developed hypertension and pre-eclampsia. Women with SPTB (vs STB) were less obese, shorter, had smaller arm circumferences and higher gravidities and Edinburgh Depression Scores, lower education, fewer telephones, and less running water at home. More women with SPTB used methamphetamine, cigarettes, and were heavier smokers.

CONCLUSION

SPTB and IPTB should not be conflated. Programs to reduce the high prevalence of SPTB should include improving education, lifestyle, and socioeconomic conditions. Addressing hypertension should help reduce preterm inductions.

Epigenetic biomarkers and preterm birth

Preterm birth (PTB) is a major public health challenge, and novel, sensitive approaches to predict PTB are still evolving. Epigenomic markers are being explored as biomarkers of PTB because of their molecular stability compared to gene expression. This approach is also relatively new compared to gene-based diagnostics, which relies on mutations or single nucleotide polymorphisms. The fundamental principle of epigenome diagnostics is that epigenetic reprogramming in the target tissue (e.g. placental tissue) might be captured by more accessible surrogate tissue (e.g. blood) using biochemical epigenome assays on circulating DNA that incorporate methylation, histone modifications, nucleosome positioning, and/or chromatin accessibility. Epigenomic-based biomarkers may hold great potential for early identification of the majority of PTBs that are not associated with genetic variants or mutations. In this review, we discuss recent advances made in the development of epigenome assays focusing on its potential exploration for association and prediction of PTB. We also summarize population-level cohort studies conducted in the USA and globally that provide opportunities for genetic and epigenetic marker development for PTB. In addition, we summarize publicly available epigenome resources and published PTB studies. We particularly focus on ongoing genome-wide DNA methylation and epigenome-wide association studies. Finally, we review the limitations of current research, the importance of establishing a comprehensive biobank, and possible directions for future studies in identifying effective epigenome biomarkers to enhance health outcomes for pregnant women at risk of PTB and their infants.

SKA2 gene - A novel biomarker for latent anxiety and preterm birth prediction

BACKGROUND

There is a relationship between preterm birth (PTB) and anxiety. Spindle and Kinetochore Associated Complex Subunit 2 (SKA2) gene polymorphism (NC_000017.11: g.59110368 G > A) has also been associated with the development of anxiety. The current study was designed to evaluate the relationship between SKA2 gene SNP (NC_000017.11: g.59110368 G > A) with the occurrence of anxiety and PTB which might be considered a predictive biomarker for the prediction of preterm delivery.

METHODS

SKA2 gene (SNP rs7208505) genotyping was performed in 300 women with term birth (TB) and 293 women with PTB using PCR-RFLP method and then followed by DNA sequencing. Cortisol level was analyzed with ELISA method and the presence of anxiety was detected using Spielberg Inventory.

RESULTS

The AA genotype of SKA2 gene significantly increased the risk of PTB compared to the GG genotype by 9.6 fold ([CI] 4.5-20.2, P < 0.001) according to codominant model. Also, the frequency of A allele was significantly higher in PTB group (χ2 = 20.4, df = 1, P < 0.001) in comparison with the control group that increased the risk of PTB by 1.703 fold ([CI] 1.39-2.23, P < 0.001). Women with higher cortisol level with average 343.7 ± 3 nmol/L had AA genotype, while, the concentrations of cortisol in women with AG, and GG genotypes were 244.2 ± 3.1 nmol/L and 192.6 ± 2.5 nmol/L, respectively (P < 0.001). The score of apparent and latent anxiety in women with the AA genotype was higher compared to the AG and GG genotypes and also this score in women with the AG genotype was higher than the GG genotypes (P < 0.001). The history of preterm delivery was higher in women with the AA genotype (42.1%) in comparison with the GG (14.9%) and AG (22%) genotypes (P < 0.05).

CONCLUSION

The results of the current study suggest that prognosis of women with the AA genotype are more susceptible to be spontaneous preterm birth. Therefore, the A allele of SKA2 gene (NC_000017.11:g.59110368 G > A) could be as a predictive biomarker for the risk of PTB.

Transcriptomic analysis of fetal membranes reveals pathways involved in preterm birth

Background

Preterm birth (PTB), defined as infant delivery before 37 weeks of completed gestation, results from the interaction of both genetic and environmental components and constitutes a complex multifactorial syndrome. Transcriptome analysis of PTB has proven challenging because of the multiple causes of PTB and the numerous maternal and fetal gestational tissues that must interact to facilitate parturition. The transcriptome of the chorioamnion membranes at the site of rupture in PTB and term fetuses may reflect the molecular pathways of preterm labor.

Methods

In this work, chorioamnion membranes from severe preterm and term fetuses were analyzed using RNA sequencing. Functional annotations and pathway analysis of differentially expressed genes were performed with the GAGE and GOSeq packages. A subset of differentially expressed genes in PTB was validated in a larger cohort using qRT-PCR and by comparing our results with genes and pathways previously reported in the literature.

Results

A total of 270 genes were differentially expressed (DE): 252 were upregulated and 18 were down-regulated in severe preterm births relative to term births. Inflammatory and immunological pathways were upregulated in PTB. Both types of pathways were previously suggested to lead to PTB. Pathways that were not previously reported in PTB, such as the hemopoietic pathway, appeared upregulated in preterm membranes. A group of 18 downregulated genes discriminated between term and severe preterm cases. These genes potentially characterize a severe preterm transcriptome pattern and therefore are candidate genes for understanding the syndrome. Some of the downregulated genes are involved in the nervous system, morphogenesis (WNT1, DLX5, PAPPA2) and ion channel complexes (KCNJ16, KCNB1), making them good candidates as biomarkers of PTB.

Conclusions

The identification of this DE gene pattern will help with the development of a multi-gene disease classifier. These markers were generated in an admixed South American population in which PTB has a high incidence. Since the genetic background may differentially impact different populations, it is necessary to include populations such as those from South America and Africa, which are usually excluded from high-throughput approaches. These classifiers should be compared to those in other populations to obtain a global landscape of PTB.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0498-3) contains supplementary material, which is available to authorized users.

Genomic and molecular characterization of preterm birth

Preterm birth (PTB) complications are the leading cause of long-term morbidity and mortality in children. By using whole blood samples, we integrated whole-genome sequencing (WGS), RNA sequencing (RNA-seq), and DNA methylation data for 270 PTB and 521 control families. We analyzed this combined dataset to identify genomic variants associated with PTB and secondary analyses to identify variants associated with very early PTB (VEPTB) as well as other subcategories of disease that may contribute to PTB. We identified differentially expressed genes (DEGs) and methylated genomic loci and performed expression and methylation quantitative trait loci analyses to link genomic variants to these expression and methylation changes. We performed enrichment tests to identify overlaps between new and known PTB candidate gene systems. We identified 160 significant genomic variants associated with PTB-related phenotypes. The most significant variants, DEGs, and differentially methylated loci were associated with VEPTB. Integration of all data types identified a set of 72 candidate biomarker genes for VEPTB, encompassing genes and those previously associated with PTB. Notably, PTB-associated genes RAB31 and RBPJ were identified by all three data types (WGS, RNA-seq, and methylation). Pathways associated with VEPTB include EGFR and prolactin signaling pathways, inflammation- and immunity-related pathways, chemokine signaling, IFN-γ signaling, and Notch1 signaling. Progress in identifying molecular components of a complex disease is aided by integrated analyses of multiple molecular data types and clinical data. With these data, and by stratifying PTB by subphenotype, we have identified associations between VEPTB and the underlying biology.

Spontaneous premature birth as a target of genomic research

Spontaneous preterm birth is a serious and common pregnancy complication associated with hormonal dysregulation, infection, inflammation, immunity, rupture of fetal membranes, stress, bleeding, and uterine distention. Heredity is 25-40% and mostly involves the maternal genome, with contribution of the fetal genome. Significant discoveries of candidate genes by genome-wide studies and confirmation in independent replicate populations serve as signposts for further research. The main task is to define the candidate genes, their roles, localization, regulation, and the associated pathways that influence the onset of human labor. Genomic research has identified some candidate genes that involve growth, differentiation, endocrine function, immunity, and other defense functions. For example, selenocysteine-specific elongation factor (EEFSEC) influences synthesis of selenoproteins. WNT4 regulates decidualization, while a heat-shock protein family A (HSP70) member 1 like, HSPAIL, influences expression of glucocorticoid receptor and WNT4. Programming of pregnancy duration starts before pregnancy and during placentation. Future goals are to understand the interactive regulation of the pathways in order to define the clocks that influence the risk of prematurity and the duration of pregnancy. Premature birth has a great impact on the duration and the quality of life. Intensification of focused research on causes, prediction and prevention of prematurity is justified.

integRATE: a desirability-based data integration framework for the prioritization of candidate genes across heterogeneous omics and its application to preterm birth

BACKGROUND

The integration of high-quality, genome-wide analyses offers a robust approach to elucidating genetic factors involved in complex human diseases. Even though several methods exist to integrate heterogeneous omics data, most biologists still manually select candidate genes by examining the intersection of lists of candidates stemming from analyses of different types of omics data that have been generated by imposing hard (strict) thresholds on quantitative variables, such as P-values and fold changes, increasing the chance of missing potentially important candidates.

METHODS

To better facilitate the unbiased integration of heterogeneous omics data collected from diverse platforms and samples, we propose a desirability function framework for identifying candidate genes with strong evidence across data types as targets for follow-up functional analysis. Our approach is targeted towards disease systems with sparse, heterogeneous omics data, so we tested it on one such pathology: spontaneous preterm birth (sPTB).

RESULTS

We developed the software integRATE, which uses desirability functions to rank genes both within and across studies, identifying well-supported candidate genes according to the cumulative weight of biological evidence rather than based on imposition of hard thresholds of key variables. Integrating 10 sPTB omics studies identified both genes in pathways previously suspected to be involved in sPTB as well as novel genes never before linked to this syndrome. integRATE is available as an R package on GitHub ( https://github.com/haleyeidem/integRATE ).

CONCLUSIONS

Desirability-based data integration is a solution most applicable in biological research areas where omics data is especially heterogeneous and sparse, allowing for the prioritization of candidate genes that can be used to inform more targeted downstream functional analyses.

Association between maternal/newborn genetic variants, placental pathology and spontaneous preterm birth risk: a Romanian population-based study

Objective: The objective of this study was to determine the association between maternal/newborn single-nucleotide polymorphisms (SNPs) in three candidate genes, placental pathology and the risk of spontaneous preterm birth (SPTB) in a Romanian population.Methods: We performed a prospective case-control study in a tertiary maternity in Romania, including 79 mother-newborn pairs with SPTB and 81 mother-newborn pairs with term delivery. Using real-time Polymerase Chain Reaction (PCR), three SNPs rs8192282 A > G, rs2277698 C > T and rs34003 A > C located on interleukin 6 receptor (IL6R), tissue inhibitor of matrix metalloproteinase-2 (TIMP2) and fibroblast growth factor 1 (FGF1) genes were assessed. The minor allele and genotype frequencies were compared between groups. Multilocus genetic association analyses were performed. From pathology reports, the morphological and histopathological examination of the placentas were extracted.Results: The rs34003 C/C genotype frequency in newborns FGF1 gene was significantly higher in the spontaneous preterm birth (SPTB) group compared to the control group (p = .045). In single-locus analyses, C/C genotype was associated with an increased risk of spontaneous preterm birth (OR = 2.59, 95%CI: 1.02-6.58). Additionally, this homozygote genotype was correlated with the presence of placental pathology, especially with the inflammatory and vascular lesions (p < .01). The prediction model based on rs34003 C/C genotype - placental pathology joint influence had a statistically significant regression coefficient (p < .01, OR = 7.76, 95%CI: 4.03-14.93). Single nucleotide polymorphisms related to IL6R gene in maternal samples and FGF1 gene in newborns were associated with spontaneous preterm delivery in multilocus genetic association analyses (p = .028, OR of 2.375).Conclusions: Our results indicate that rs34003 C/C genotype in newborns FGF1gene is correlated with the occurrence of placental pathological lesions and with an increased SPTB risk. The association of two SNPs in maternal and fetal genes doubled the risk of spontaneous preterm birth in our population.

Pre-Pregnancy Health Status and Risk of Preterm Birth: A Large, Chinese, Rural, Population-Based Study

The aim of this study was to estimate the incidence of preterm birth (PTB) and identify maternal risk factors before pregnancy in rural China, and to determine their population-attributable fractions (PAFs).

A prospectively population-based study was conducted in the city of Fuyang, China. Surveillance locations were randomly selected by cluster sampling based on administrative areas and geographic characteristics. Data were collected through interview questionnaires and medical examination records from the participants, then follow-up until discharge, fetus death, or at a maximum of 6 weeks postpartum, whichever came first. We used logistic regression analysis to identify the associated factors. PAFs were also estimated to examine the impact of risk factors.

The incidence of PTB was 3.86% in this study. Multivariate analyses showed that risk factors for PTB were economic pressure (aOR=2.98, 95% CI, 2.40–3.71), hypertension (aOR=3.45, 95% CI, 2.23–5.36), hypoglycemia (aOR=2.07, 95% CI, 1.58, 2.72), hyperglycemia (aOR=1.69, 95% CI, 1.09, 2.62), serum creatinine (<44 μmol/L) (aOR=1.78, 95% CI, 1.13–2.40), hypothyroidism (aOR=1.37, 95% CI, 1.06–1.78), positivity for anti-CMV IgM (aOR=2.57, 95% CI, 1.21–5.45), multiple pregnancy (aOR=3.35, 95% CI, 1.87–6.00), and parity (≥3 times) (aOR=1.67, 95% CI, 1.05–2.64). Economic pressure was the most significant contributor (11.57%), while parity was the lowest (0.10%).

This study demonstrated the relatively high burden of PTBs in a rural Chinese area. A broader focus on the risk factors prior to pregnancy amenable to interventions of women may reduce the incidence of PTB.

Genetic studies of gestational duration and preterm birth

The fine control of birth timing is important to human survival and evolution. A key challenge in studying the mechanisms underlying the regulation of human birth timing is that human parturition is a unique to human event — animal models provide only limited information. The duration of gestation or the risk of preterm birth is a complex human trait under genetic control from both maternal and fetal genomes. Genomic discoveries through genome-wide association (GWA) studies would implicate relevant genes and pathways. Similar to other complex human traits, gestational duration is likely to be influenced by numerous genetic variants of small effect size. The detection of these small-effect genetic variants requires very large sample sizes. In addition, several practical and analytical challenges, in particular the involvement of both maternal and fetal genomes, further complicate the genetic studies of gestational duration and other pregnancy phenotypes. Despite these challenges, large-scale GWA studies have already identified several genomic loci associated with gestational duration or the risk of preterm birth. These genomic discoveries have revealed novel insights about the biology of human birth timing. Expanding genomic discoveries in larger datasets by more refined analytical approaches, together with the functional analysis of the identified genomic loci, will collectively elucidate the biological processes underlying the control of human birth timing.

A Handy Preterm Infant Incubator for Providing Intensive Care: Simulation, 3D Printed Prototype, and Evaluation

Preterm infants encounter an abrupt delivery before their complete maturity during the third trimester of pregnancy. Polls anticipate an increase in the rates of preterm infants for 2025, especially in middle- and low-income countries. Despite the abundance of intensive care methods for preterm infants, such as, but not limited to, commercial, transport, embrace warmer, radiant warmer, and Kangaroo Mother Care methods, they are either expensive, lack the most essential requirements or specifications, or lack the maternal-preterm bond. This drove us to carry this original research and innovative idea of developing a new 3D printed prototype of a Handy preterm infant incubator. We aim to provide the most indispensable intensive care with the lowest cost, to bestow low-income countries with the Handy incubator's care, preserve the maternal -preterm's bond, and diminish the rate of mortality. Biomedical features, electronics, and biocompatible materials were utilized. The design was simulated, the prototype was 3D printed, and the outcomes were tested and evaluated. Simulation results showed the best fit for the Handy incubator's components. Experimental results showed the 3D-printed prototype and the time elapsed to obtain it. Evaluation results revealed that the overall performance of Kangaroo Mother Care and the embrace warmer was 75 ± 1.4% and 66.7 ± 1.5%, respectively, while the overall performance of our Handy incubator was 91.7 ± 1.6%, thereby our cost-effective Handy incubator surpassed existing intensive care methods. The future step is associating the Handy incubator with more specifications and advancements.

Maternal periodontal disease and adverse perinatal outcomes: is there an association? A hospital-based case-control study

Objectives: The association between maternal periodontal disease and adverse perinatal outcomes although extensively studied remains unclear. The aim of this study was to evaluate, by a case-control study, conducted in three hospitals the association between preterm birth and/or low birth weight (PTB/LBW) and clinical parameters of maternal periodontal disease. Material and methods: Postpartum women who gave birth to a newborn PTB/LBW (case group), and postpartum women who had babies at full term with normal weight (control group) were included, in 1:2 ratio. Data were collected through medical records, interview, and periodontal clinical parameters. Bivariate analysis was performed to assess the PTB/LBW proportion relative to independent variables and multiple logistic regression analysis to assess the association between adverse perinatal outcomes and independent variables. Results: The sample consisted of 148 cases and 296 controls. By the 148 postpartum women with PTB/LBW in case group, 126 (87.5%) had preterm birth, and 75 (50.7%) had PTB and LBW. The periodontal status and generalized periodontitis presence were not associated with any adverse pregnancy outcomes. Having made four or more prenatal visits was a protective factor for all outcomes. The history of previous PTB/LBW was a risk factor for new cases of PTB and PTB and/or LBW. The presence of systemic disease was associated with preterm and low birth weight (PTLBW). Preeclampsia and cesarean delivery were associated with all outcomes. Conclusions: The clinical parameters of maternal periodontitis were not considered as a risk factor for the studied adverse perinatal outcomes. Clinical relevance: The present study demonstrated no association between maternal periodontitis and PTB/LBW.

Understanding biological mechanisms underlying adverse birth outcomes in developing countries: protocol for a prospective cohort (AMANHI bio-banking) study

Objectives

The AMANHI study aims to seek for biomarkers as predictors of important pregnancy–related outcomes, and establish a biobank in developing countries for future research as new methods and technologies become available.

Methods

AMANHI is using harmonised protocols to enrol 3000 women in early pregnancies (8–19 weeks of gestation) for population–based follow–up in pregnancy up to 42 days postpartum in Bangladesh, Pakistan and Tanzania, with collection taking place between August 2014 and June 2016. Urine pregnancy tests will be used to confirm reported or suspected pregnancies for screening ultrasound by trained sonographers to accurately date the pregnancy. Trained study field workers will collect very detailed phenotypic and epidemiological data from the pregnant woman and her family at scheduled home visits during pregnancy (enrolment, 24–28 weeks, 32–36 weeks & 38+ weeks) and postpartum (days 0–6 or 42–60). Trained phlebotomists will collect maternal and umbilical blood samples, centrifuge and obtain aliquots of serum, plasma and the buffy coat for storage. They will also measure HbA1C and collect a dried spot sample of whole blood. Maternal urine samples will also be collected and stored, alongside placenta, umbilical cord tissue and membrane samples, which will both be frozen and prepared for histology examination. Maternal and newborn stool (for microbiota) as well as paternal and newborn saliva samples (for DNA extraction) will also be collected. All samples will be stored at –80°C in the biobank in each of the three sites. These samples will be linked to numerous epidemiological and phenotypic data with unique study identification numbers.

Importance of the study

AMANHI biobank proves that biobanking is feasible to implement in LMICs, but recognises that biobank creation is only the first step in addressing current global challenges.

A genome-wide association study identifies only two ancestry specific variants associated with spontaneous preterm birth

Preterm birth (PTB), or the delivery prior to 37 weeks of gestation, is a significant cause of infant morbidity and mortality. Although twin studies estimate that maternal genetic contributions account for approximately 30% of the incidence of PTB, and other studies reported fetal gene polymorphism association, to date no consistent associations have been identified. In this study, we performed the largest reported genome-wide association study analysis on 1,349 cases of PTB and 12,595 ancestry-matched controls from the focusing on genomic fetal signals. We tested over 2 million single nucleotide polymorphisms (SNPs) for associations with PTB across five subpopulations: African (AFR), the Americas (AMR), European, South Asian, and East Asian. We identified only two intergenic loci associated with PTB at a genome-wide level of significance: rs17591250 (P = 4.55E-09) on chromosome 1 in the AFR population and rs1979081 (P = 3.72E-08) on chromosome 8 in the AMR group. We have queried several existing replication cohorts and found no support of these associations. We conclude that the fetal genetic contribution to PTB is unlikely due to single common genetic variant, but could be explained by interactions of multiple common variants, or of rare variants affected by environmental influences, all not detectable using a GWAS alone.

Investigating the Prevalence of Preterm Birth in Iranian Population: A Systematic Review and Meta-Analysis

Introduction: Despite medical advances, preterm delivery remains a global problem in developed and developing countries. The present study was aimed at conducting a systematic review and meta-analysis of studies on the prevalence of preterm delivery in Iran.

Methods: This study was carried out on studies conducted in Iran by searching databases of SID, Magiran, Irandoc, MEDLIB, Iranmedex, PubMed, Web of science, Google Scholar and Scopus. The search was conducted using advanced search and keywords of preterm delivery and equivalents of it in Mesh and their Farsi’s Synonymous in all articles from 2000-2016.After extracting the data, the data were combined using a random model. Heterogeneity of the studies was assessed using Q test I2 index and the data were analyzed using STATA Ver.11 software.

Results: The total number of samples in this study was 41773. In 19 reviewed articles, the overall prevalence of preterm delivery, based on the random effects model, was estimated to be a total of 10% (95% CI, 9-12). The lowest prevalence of preterm labor was 5.4% in Bam and the highest prevalence was 19.85% in Tehran. There was no significant difference between the prevalence of preterm delivery compared to year of study and sample size.

Conclusion: This study reviewed the findings of previous studies and showed that preterm delivery is a relatively prevalent problem in Iran. Therefore, adopting appropriate interventions in many cases including life skills training, self-care and increasing pregnancy care to reduce these consequences and their following complications in high risk patients seem necessary.

Conceptualizing pathways linking women's empowerment and prematurity in developing countries

BACKGROUND

Globally, prematurity is the leading cause of death in children under the age of 5. Many efforts have focused on clinical approaches to improve the survival of premature babies. There is a need, however, to explore psychosocial, sociocultural, economic, and other factors as potential mechanisms to reduce the burden of prematurity. Women's empowerment may be a catalyst for moving the needle in this direction. The goal of this paper is to examine links between women's empowerment and prematurity in developing settings. We propose a conceptual model that shows pathways by which women's empowerment can affect prematurity and review and summarize the literature supporting the relationships we posit. We also suggest future directions for research on women's empowerment and prematurity.

METHODS

The key words we used for empowerment in the search were "empowerment," "women's status," "autonomy," and "decision-making," and for prematurity we used "preterm," "premature," and "prematurity." We did not use date, language, and regional restrictions. The search was done in PubMed, Population Information Online (POPLINE), and Web of Science. We selected intervening factors-factors that could potentially mediate the relationship between empowerment and prematurity-based on reviews of the risk factors and interventions to address prematurity and the determinants of those factors.

RESULTS

There is limited evidence supporting a direct link between women's empowerment and prematurity. However, there is evidence linking several dimensions of empowerment to factors known to be associated with prematurity and outcomes for premature babies. Our review of the literature shows that women's empowerment may reduce prematurity by (1) preventing early marriage and promoting family planning, which will delay age at first pregnancy and increase interpregnancy intervals; (2) improving women's nutritional status; (3) reducing domestic violence and other stressors to improve psychological health; and (4) improving access to and receipt of recommended health services during pregnancy and delivery to help prevent prematurity and improve survival of premature babies.

CONCLUSIONS

Women's empowerment is an important distal factor that affects prematurity through several intervening factors. Improving women's empowerment will help prevent prematurity and improve survival of preterm babies. Research to empirically show the links between women's empowerment and prematurity is however needed.

Genome-wide approach identifies a novel gene-maternal pre-pregnancy BMI interaction on preterm birth

Preterm birth (PTB) contributes significantly to infant mortality and morbidity with lifelong impact. Few robust genetic factors of PTB have been identified. Such 'missing heritability' may be partly due to gene × environment interactions (G × E), which is largely unexplored. Here we conduct genome-wide G × E analyses of PTB in 1,733 African-American women (698 mothers of PTB; 1,035 of term birth) from the Boston Birth Cohort. We show that maternal COL24A1 variants have a significant genome-wide interaction with maternal pre-pregnancy overweight/obesity on PTB risk, with rs11161721 (PG × E=1.8 × 10-8; empirical PG × E=1.2 × 10-8) as the top hit. This interaction is replicated in African-American mothers (PG × E=0.01) from an independent cohort and in meta-analysis (PG × E=3.6 × 10-9), but is not replicated in Caucasians. In adipose tissue, rs11161721 is significantly associated with altered COL24A1 expression. Our findings may provide new insight into the aetiology of PTB and improve our ability to predict and prevent PTB.

Rare mutations and potentially damaging missense variants in genes encoding fibrillar collagens and proteins involved in their production are candidates for risk for preterm premature rupture of membranes

Preterm premature rupture of membranes (PPROM) is the leading identifiable cause of preterm birth with ~ 40% of preterm births being associated with PPROM and occurs in 1% - 2% of all pregnancies. We hypothesized that multiple rare variants in fetal genes involved in extracellular matrix synthesis would associate with PPROM, based on the assumption that impaired elaboration of matrix proteins would reduce fetal membrane tensile strength, predisposing to unscheduled rupture. We performed whole exome sequencing (WES) on neonatal DNA derived from pregnancies complicated by PPROM (49 cases) and healthy term deliveries (20 controls) to identify candidate mutations/variants. Genotyping for selected variants from the WES study was carried out on an additional 188 PPROM cases and 175 controls. All mothers were self-reported African Americans, and a panel of ancestry informative markers was used to control for genetic ancestry in all genetic association tests. In support of the primary hypothesis, a statistically significant genetic burden (all samples combined, SKAT-O p-value = 0.0225) of damaging/potentially damaging rare variants was identified in the genes of interest-fibrillar collagen genes, which contribute to fetal membrane strength and integrity. These findings suggest that the fetal contribution to PPROM is polygenic, and driven by an increased burden of rare variants that may also contribute to the disparities in rates of preterm birth among African Americans.

Effect of maternal and neonatal interleukin-6 - 174 G/C polymorphism on preterm birth and neonatal morbidity

OBJECTIVE

The aim of this study was to analyze maternal and neonatal interleukin 6 (IL-6) (-174 G/C) polymorphism and to determine effect on preterm birth and neonatal morbidity.

STUDY DESIGN

One hundred and sixty-four mothers (100 term births, 64 preterm births) and 183 newborn infants who were 100 healthy term and 83 preterm babies followed in newborn intensive care units were evaluated. PCR-RFLP was performed for IL-6 (-174 G/C) genotyping.

RESULTS

The rate of GG genotype in mothers of term and preterm infants were 54% (n = 54/100), 75% (n = 48/64), respectively (p > .05) and the rate of GC + CC genotype was 46% (n = 46/100) and 25% (n = 16/64) in mothers giving term and preterm birth (PTB), respectively (p < .05). Additionally, the rate of GG genotype was 65% (n = 65/100) and 81.9% (n = 68/83) in term infants and preterm infants, respectively. GC + CC genotype was 35% (n = 35/100) in term infants and 18.1% (n = 15/83) in preterm infants (p < .05). The effect of IL-6 (-174) GC + CC genotype on PTB was statistically significant.

CONCLUSION

The IL-6 174 G/C gene polymorphism was significantly different between mothers who were giving to term and preterm birth. The presence of polymorphism is protective against preterm birth and was not associated with neonatal outcome.

Maternal IGF1 and IGF1R polymorphisms and the risk of spontaneous preterm birth

BACKGROUND

The insulin-like growth factor (IGF) pathway was involved in the occurrence of spontaneous preterm birth (SPTB), but little is known regarding the relationship between genetic variations in IGF pathway and the risk of SPTB. We aimed to investigate the associations of IGF1 rs972936 and IGF1 receptor (IGF1R) rs2229765 polymorphisms with SPTB risk in a Chinese population.

METHOD

A total of 114 cases of SPTB and 250 controls of term delivery were included from Guangzhou Women and Children's Medical Center, China. The odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated using multivariate logistic regression.

RESULTS

We found that the GA and GA/AA genotypes of IGF1 rs972936 were associated with an increased risk of SPTB, and the adjusted ORs (95% CI) were 1.74 (1.01-3.02) and 1.75 (1.04-2.93) respectively. Women carrying GA and GA/AA genotypes of IGF1R rs2229765 had a reduced risk compared to those with the GG genotype (0.60 [0.37-0.98] and 0.64 [0.40-1.00] respectively). There were significant interactions between IGF1 rs972936 and GDM status (P for interaction=.02), as well as between IGF1R rs2229765 and pre-pregnancy BMI (P for interaction <.001) on the risk of SPTB.

CONCLUSION

Our findings suggest that polymorphisms of IGF1 rs972936 and IGF1R rs2229765 were associated with the risk of SPTB in Chinese pregnant women and these effects depend on the maternal metabolic status.

Reducing Low Birth Weight among African Americans in the Midwest: A Look at How Faith-Based Organizations Are Poised to Inform and Influence Health Communication on the Developmental Origins of Health and Disease (DOHaD)

Low birth weight (LBW) rates remain the highest among African Americans despite public health efforts to address these disparities; with some of the highest racial disparities in the Midwest (Kansas). The Developmental Origins of Health and Disease (DOHaD) perspective offers an explanation for how LBW contributes to racial health disparities among African Americans and informs a community directed health communication framework for creating sustainable programs to address these disparities. Trusted community organizations such as faith-based organizations are well situated to explain health communication gaps that may occur over the life course. These entities are underutilized in core health promotion programming targeting underserved populations and can prove essential for addressing developmental origins of LBW among African Americans. Extrapolating from focus group data collected from African American church populations as part of a social marketing health promotion project on cancer prevention, we theoretically consider how a similar communication framework and approach may apply to address LBW disparities. Stratified focus groups (n = 9) were used to discover emergent themes about disease prevention, and subsequently applied to explore how faith-based organizations (FBOs) inform strategic health care (media) advocacy and health promotion that potentially apply to address LBW among African Americans. We argue that FBOs are poised to meet health promotion and health communication needs among African American women who face social barriers in health.

Preterm Birth: Analysis of Longitudinal Data on Siblings Based on Random-Effects Logit Models

INTRODUCTION

The literature about the determinants of a preterm birth is still controversial. We approach the analysis of these determinants distinguishing between woman's observable characteristics, which may change over time, and unobservable woman's characteristics, which are time invariant and explain the dependence between the typology (normal or preterm) of consecutive births.

METHODS

We rely on a longitudinal dataset about 28,603 women who delivered for the first time in the period 2005-2013 in the Umbria Region (Italy). We consider singleton physiological pregnancies originating from natural conceptions with birthweight of at least 500 g and gestational age between 24 and 42 weeks; the overall number of deliveries is 34,224. The dataset is based on the Standard Certificates of Life Birth collected in the region in the same period. We estimate two types of logit model for the event that the birth is preterm. The first model is pooled and accounts for the information about possible previous preterm deliveries, including the lagged response among the covariates. The second model takes explicitly into account the longitudinal structure of data through the introduction of a random effect that summarizes all the (time invariant) unobservable characteristics of a woman affecting the probability of a preterm birth.

RESULTS

The estimated models provide evidence that the probability of a preterm birth depends on certain woman's demographic and socioeconomic characteristics, other than on the previous history in terms of miscarriages and the baby's gender. Besides, as the random-effects model fits significantly better than the pooled model with lagged response, we conclude for a spurious state dependence between repeated preterm deliveries.

CONCLUSION

The proposed analysis represents a useful tool to detect profiles of women with a high risk of preterm delivery. Such profiles are detected taking into account observable woman's demographic and socioeconomic characteristics as well as unobservable and time-constant characteristics, possibly related to the woman's genetic makeup.

TRIAL REGISTRATION

Not applicable.

Structural and genomic variation in preterm birth

BACKGROUND

Runs of homozygosity (ROH) are consecutive homozygous genotypes, which may result from population inbreeding or consanguineous marriages. ROH enhance the expression of recessive traits.

METHODS

We mapped ROH in a case control study of women delivering at term compared with women delivering at or before 34 wk gestation. Gene sets known to be important in risk of preterm birth were examined for their overlap with identified ROH segments.

RESULTS

While we found no evidence of increased burden of ROH or copy number variations in mothers delivering at or before 34 wk compared with term, we identified 424 genome-wide 50 kb segments with significant difference in abundance of overlapping ROH segments in cases vs. controls, P < 0.05. These regions overlap 199 known genes. We found preterm birth associated genes (CXCR4, MYLK, PAK1) and genes shown to have an evolutionary link to preterm (CXCR4, PPP3CB, C6orf57, DUSP13, and SLC25A45) with significant differences in abundance of overlapping ROH blocks in cases vs. controls, P < 0.001.

CONCLUSION

We conclude, while we found no significant burden of ROH, we did identify genomic regions with significantly greater abundance of ROH blocks in women delivering preterm that overlapped genes known to be involved in preterm birth.

Characterization of mothers at risk of delivery at the limit of viability and factors related to infant survival

OBJECTIVES

To determine the sociodemographic and clinical characteristics of mothers of infants at the limit of viability and to know the perinatal factors associated to infants' survival.

METHOD

Single-center cohort study of mothers and newborns assisted in our tertiary care center (2004-2010). Demographic and perinatal variables were compared between mothers who gave birth  ≤26 weeks GA and the general population. The association between perinatal factors and neonatal survival was studied by Cox regression analysis.

RESULTS

Mothers of newborns  ≤26 weeks (n = 136) had less education and pregnancy control. They had more frequently assisted reproductive technologies (ART) (5.2% versus 2.3%; p< 0.05), multiple gestations (16.6% versus 2.1%; p < 0.05), pregnancy complications and C-section (39.7% versus 13.4%; p  < 0.001). After correcting for confounders, the perinatal factors independently associated with a variation in the risk of mortality were the administration of antenatal steroid [aHR (95%CI): 0.465 (0.254-0.853), p = 0.013], singleton pregnancy [aHR (95%CI): 0.482 (0.279-0.834), p = 0.009], infant's temperature on admission [aHR (95%CI): 0.642 (0.426-0.968), p = 0.035] and CRIB score [aHR (95%CI): 1.151 (1.058-1.251), p  = 0.001].

CONCLUSIONS

Mothers of preterm infants at the limit of viability had more ART, multiple pregnancies, obstetrical complications and C-section. Infants' survival was independently associated to antenatal steroids, singleton pregnancy, temperature on admission and CRIB score.

Targeted Sequencing and Meta-Analysis of Preterm Birth

Understanding the genetic contribution(s) to the risk of preterm birth may lead to the development of interventions for treatment, prediction and prevention. Twin studies suggest heritability of preterm birth is 36–40%. Large epidemiological analyses support a primary maternal origin for recurrence of preterm birth, with little effect of paternal or fetal genetic factors. We exploited an “extreme phenotype” of preterm birth to leverage the likelihood of genetic discovery. We compared variants identified by targeted sequencing of women with 2–3 generations of preterm birth with term controls without history of preterm birth. We used a meta-genomic, bi-clustering algorithm to identify gene sets coordinately associated with preterm birth. We identified 33 genes including 217 variants from 5 modules that were significantly different between cases and controls. The most frequently identified and connected genes in the exome library were IGF1, ATM and IQGAP2. Likewise, SOS1, RAF1 and AKT3 were most frequent in the haplotype library. Additionally, SERPINB8, AZU1 and WASF3 showed significant differences in abundance of variants in the univariate comparison of cases and controls. The biological processes impacted by these gene sets included: cell motility, migration and locomotion; response to glucocorticoid stimulus; signal transduction; metabolic regulation and control of apoptosis.

Is Self-Regulation "All in the family"? Testing Environmental Effects using Within-Family Quasi-Experiments

Most of the individual difference variance in the population is found within families, yet studying the processes causing this variation is difficult due to confounds between genetic and nongenetic influences. Quasi-experiments can be used to test hypotheses regarding environment exposure (e.g., timing, duration) while controlling for genetic confounds. To illustrate, two studies of cognitive self-regulation in childhood (i.e., working memory [WM], effortful control [EC], attention span/persistence [A/P]) are presented. Study 1 utilized an identical twin differences design (N = 85 to 98 pairs) to control for genetic differences while using relative twin birth weight difference to predict relative twin difference in WM and EC. Larger relative twin difference in WM and EF was predicted by the combination of shorter gestation and larger relative birth weight difference. Study 2 utilized an adoptive sibling relative difference design (N = 123 same-sex pairs) to control for genetic similarity while using relative sibling difference in the age at time of adoption to predict relative sibling difference in A/P. Larger relative sibling difference in A/P was predicted by the combination of larger relative difference in time in the adoptive home and age at adoption. Within-family quasi-experimental designs allow stronger inferences about hypothesized environmental influences than between-family designs permit.

Polymorphisms in NR5A2, gene encoding liver receptor homolog-1 are associated with preterm birth

BACKGROUND

Preterm birth (PTB) is a major cause of neonatal mortality and morbidity. There is strong evidence of genetic susceptibility. Objective of this study was to identify genetic variants contributing to PTB.

METHODS

Genotyping was performed for 24 single nucleotide polymorphisms (SNPs) in 4 candidate genes (NR5A2, FSHR, FOXP3, and SERPINH1). Genotyping was completed on 728 maternal triads (mother and maternal grandparents of a preterm infant). Data were analyzed with Family Based Association Test.

RESULTS

For all maternal triads rs2737667 of NR5A2 showed significant association at P = 0.02. When stratifying by gestational age three SNPs in NR5A2 had P values <0.05 in the <32-wk gestational age group (rs12131233, P = 0.007; rs2737667, P = 0.04; rs2816949, P = 0.02). When preterm premature rupture of membranes cases were excluded rs2737667 of NR5A2 showed the strongest association with a P value <0.0002. This association remained significant after correction for multiple testing.

CONCLUSION

This study suggests a potential association between intronic SNPs in the NR5A2 gene and PTB. NR5A2 gene encodes for the liver receptor homolog-1 protein, which plays a critical role in regulation of cholesterol metabolism, steroidogenesis, and progesterone synthesis. These findings suggest that NR5A2 may be important in the pathophysiology of PTB and exploring noncoding regulators of NR5A2 is warranted.

The genomics of prematurity in an era of more precise clinical phenotyping: A review

Spontaneous preterm birth is a major public health problem, with a clear genetic component. Genetic association studies have evolved substantially in recent years, moving away from the traditional candidate gene analyses to newer approaches utilizing sophisticated analysis platforms to examine sequencing data, and shifting towards functional studies including methylation analysis. It is becoming increasingly evident that careful clinical phenotyping is crucial to high quality genetic association studies regardless of the assay or platform being used. Nonetheless, genetic studies of prematurity are hampered by numerous challenges including small sample sizes, incomplete phenotying, population stratification, and multiple comparisons. As the costs of sequencing and functional analyses continue to decrease, unbiased genome-wide assays will be more widely available. Researchers have met improved success recently when critically applying clinical phenotyping knowledge to group women prior to analyzing genotyping results. Eventually, as the analytic approaches evolve, it is likely that this methodology (combining precisely clinically phenotyped subjects with genome-wide data) will provide key information regarding the pathophysiology of prematurity, and provide potential new avenues for exploring innovative therapeutic strategies.

Comparing human and macaque placental transcriptomes to disentangle preterm birth pathology from gestational age effects

INTRODUCTION

A major issue in the transcriptomic study of spontaneous preterm birth (sPTB) in humans is the inability to collect healthy control tissue at the same gestational age (GA) to compare with pathologic preterm tissue. Thus, gene expression differences identified after the standard comparison of sPTB and term tissues necessarily reflect differences in both sPTB pathology and GA. One potential solution is to use GA-matched controls from a closely related species to tease apart genes that are dysregulated during sPTB from genes that are expressed differently as a result of GA effects.

METHODS

To disentangle genes whose expression levels are associated with sPTB pathology from those linked to GA, we compared RNA sequencing data from human preterm placentas, human term placentas, and rhesus macaque placentas at 80% completed gestation (serving as healthy non-human primate GA-matched controls). We first compared sPTB and term human placental transcriptomes to identify significantly differentially expressed genes. We then overlaid the results of the comparison between human sPTB and macaque placental transcriptomes to identify sPTB-specific candidates. Finally, we overlaid the results of the comparison between human term and macaque placental transcriptomes to identify GA-specific candidates.

RESULTS

Examination of relative expression for all human genes with macaque orthologs identified 267 candidate genes that were significantly differentially expressed between preterm and term human placentas. 29 genes were identified as sPTB-specific candidates and 37 as GA-specific candidates. Altogether, the 267 differentially expressed genes were significantly enriched for a variety of developmental, metabolic, reproductive, immune, and inflammatory functions. Although there were no notable differences between the functions of the 29 sPTB-specific and 37 GA-specific candidate genes, many of these candidates have been previously shown to be dysregulated in diverse pregnancy-associated pathologies.

DISCUSSION

By comparing human sPTB and term transcriptomes with GA-matched control transcriptomes from a closely related species, this study disentangled the confounding effects of sPTB pathology and GA, leading to the identification of 29 promising sPTB-specific candidate genes and 37 genes potentially related to GA effects. The apparent similarity in functions of the sPTB and GA candidates may suggest that the effects of sPTB and GA do not correspond to biologically distinct processes. Alternatively, it may reflect the poor state of knowledge of the transcriptional landscape underlying placental development and disease.

Oxidative stress damage-associated molecular signaling pathways differentiate spontaneous preterm birth and preterm premature rupture of the membranes

STUDY HYPOTHESIS

In women with preterm premature rupture of the membranes (PPROM), increased oxidative stress may accelerate premature cellular senescence, senescence-associated inflammation and proteolysis, which may predispose them to rupture.

STUDY FINDING

We demonstrate mechanistic differences between preterm birth (PTB) and PPROM by revealing differences in fetal membrane redox status, oxidative stress-induced damage, distinct signaling pathways and senescence activation.

WHAT IS KNOWN ALREADY

Oxidative stress-associated fetal membrane damage and cell cycle arrest determine adverse pregnancy outcomes, such as spontaneous PTB and PPROM.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Fetal membranes and amniotic fluid samples were collected from women with PTB and PPROM. Molecular, biochemical and histologic markers were used to document differences in oxidative stress and antioxidant enzyme status, DNA damage, secondary signaling activation by Ras-GTPase and mitogen-activated protein kinases, and activation of senescence between membranes from the two groups.

MAIN RESULTS AND THE ROLE OF CHANCE

Oxidative stress was higher and antioxidant enzymes were lower in PPROM compared with PTB. PTB membranes had minimal DNA damage and showed activation of Ras-GTPase and ERK/JNK signaling pathway with minimal signs of senescence. PPROM had higher numbers of cells with DNA damage, prosenescence stress kinase (p38 MAPK) activation and signs of senescence.

LIMITATIONS, REASONS FOR CAUTION

Samples were obtained retrospectively after delivery. The markers of senescence that we tested are specific but are not sufficient to confirm senescence as the pathology in PPROM.

WIDER IMPLICATIONS OF THE FINDINGS

Oxidative stress-induced DNA damage and senescence are characteristics of fetal membranes from PPROM, compared with PTB with intact membranes. PTB and PPROM arise from distinct pathophysiologic pathways. Oxidative stress and oxidative stress-induced cellular damages are likely determinants of the mechanistic signaling pathways and phenotypic outcome.

STUDY FUNDING AND COMPETING INTERESTS

This study is supported by developmental funds to Dr R. Menon from the Department of Obstetrics and Gynecology at The University of Texas Medical Branch at Galveston and funds to Dr M. Kacerovský from the Ministry of Health Czech Republic (UHHK, 001799906). The authors report no conflict of interest.

Clinical and prognostic value of combined measurement of cytokines and vascular cell adhesion molecule-1 in premature rupture of membranes

OBJECTIVE

To evaluate whether levels of interleukin 6 (IL-6), interleukin 8 (IL-8), and vascular cell adhesion molecule-1 (VCAM-1) in women with premature rupture of membranes (PROM) differ from those in women without PROM.

METHODS

An observational study of full-term primiparous pregnant women with PROM (PROM group) and those undergoing elective cesarean delivery (control group) was performed at a center in Yangzhou, China, between January 2003 and July 2006. IL-6, IL-8, and VCAM-1 levels were measured in maternal blood, cord blood, and amniotic fluid. A pathologic examination of fetal membranes was conducted.

RESULTS

The IL-6, IL-8, and VCAM-1 levels in maternal serum, amniotic fluid, and cord blood were significantly higher in the PROM group (n=58) than in the control group (n=38; P<0.05 for all comparisons). In the PROM group, the levels increased with duration of membrane rupture (P<0.05 for all). Women with chorioamnionitis had significantly higher levels than women without chorioamnionitis (P<0.05 for all), and women with PROM whose newborns had low Apgar score (≤7) had higher levels than those whose newborns had a higher Apgar score (P<0.05 for all).

CONCLUSION

Combined measurements of IL-6, IL-8, and VCAM-1 might help to improve early diagnosis of PROM and chorioamnionitis, and to evaluate the prognosis of newborns.

Association between the Lipid Levels and Single Nucleotide Polymorphisms of ABCA1, APOE and HMGCR Genes in Subjects with Spontaneous Preterm Delivery

Spontaneous preterm delivery (SPTD) with gestational age between 28 and 37 complete weeks was reported to have a genetic predisposition in lipids metabolism. This study aimed to investigate the association between the lipid levels and gene polymorphisms of ABCA1 (rs2422493), APOE (rs7412) and HMGCR (rs12916) in Chinese pregnant women with SPTD. A case-control study was conducted at the baseline randomization in 200 SPTD and 178 healthy full term delivery (FTD) women. Maternal blood lipids were detected close to delivery of fetus in SPTD group and in FTD group with gestational age-matched. Cord blood lipids were detected after delivery in two groups. Three genotypes both in maternal and cord blood were determined by real time PCR. The results showed that the levels of total cholesterol (TCHO), triglyceride (TG), high density lipoprotein (HDL), and low-density lipoprotein cholesterol (LDL) in the maternal blood in the SPTD group were significantly lower than those in the FTD group, while the levels of TCHO, HDL, and LDL in the cord blood in the SPTD group were significantly higher than those in the FTD group. In the SPTD subjects, the levels of TG and LDL in the maternal blood were associated with different genotypes of HMGCR gene rs12916 loci. These results indicate that abnormal lipid metabolism may exist in SPTD women and the premature fetus and the HMGCR gene may be a susceptible gene for SPTD.

CXCR3 Polymorphism and Expression Associate with Spontaneous Preterm Birth

Spontaneous preterm birth (SPTB) is a major factor associating with deaths and with lowered quality of life in humans. Environmental and genetic factors influence the susceptibility. Previously, by analyzing families with recurrent SPTB in linkage analysis, we identified a linkage peak close to the gene encoding CXCR3. Present objectives were to investigate the association of CXCR3 with SPTB in Finnish mothers (n = 443) and infants (n = 747), to analyze CXCR3 expression levels in human placenta and levels of its ligands in umbilical cord blood, and to verify the influence of Cxcr3 on SPTB-associating cytokines in mice. We detected an association between an intronic CXCR3 polymorphism, rs2280964, and SPTB in infants from families with recurrent preterm births (p = 0.009 versus term controls, odds ratio 0.52, 95% confidence interval 0.32-0.86). The minor allele was protective and undertransmitted to SPTB infants (p = 0.007). In the placenta and fetal membranes, the rs2280964 major allele homozygotes had higher expression levels than minor allele homozygotes; decidual trophoblasts showed strong CXCR3 immunoreactivity. Expression was higher in SPTB placentas compared with those from elective deliveries. Concentration of a CXCR3 ligand, CXCL9, was increased in cord blood from SPTB, and the protective rs2280964 allele was associated with low CXCL9. In CXCR3-deficient mice (Mus musculus), SPTB-associating cytokines were not acutely increased in amniotic fluid after preterm birth-inducing dose of maternal LPS. Our results indicate that CXCR3 contributes to SPTB. Activation of CXCR3 signaling may disturb the maternal-fetal tolerance, and this may promote labor.