Maternal effects for preterm birth: a genetic epidemiologic study of 630,000 families

Protective Effect of EBF Transcription Factor 1 (EBF1) Polymorphism in Sporadic and Familial Spontaneous Preterm Birth: Insights from a Case-Control Study

This study investigated the potential role of specific single-nucleotide polymorphisms (SNPs) in the genes Astrotactin 1 (ASTN1), EBF Transcription Factor 1 (EBF1), Eukaryotic Elongation Factor, Selenocysteine-tRNA Specific (EEFSEC), Microtubule-Associated Serine/Threonine Kinase 1 (MAST1), and Tumor Necrosis Factor Alpha (TNF-α) to assess whether these genetic variants contribute to the risk of spontaneous preterm birth (sPTB). A case-control study was conducted involving 573 women from Croatia and Slovenia: 248 with sporadic sPTB (positive personal and negative family history of sPTB before 37 weeks' gestation), 44 with familial sPTB (positive personal and family history of sPTB before 37 weeks' gestation), and 281 control women. The analysis of ASTN1 rs146756455, EBF1 rs2963463, EBF1 rs2946169, EEFSEC rs201450565, MAST1 rs188343966, and TNF-α rs1800629 SNPs was performed using TaqMan real-time PCR. p-values were Bonferroni-adjusted for multiple comparisons. EBF1 SNP rs2963463 was significantly associated with sPTB (p adj = 0.03). Women carrying the CC genotype had a 3-4-times lower risk of sPTB (p adj < 0.0001). In addition, a significant difference in the frequency of the minor C allele was observed when comparing familial sPTB cases with controls (p adj < 0.0001). All other associations were based on unadjusted p-values. The minor T allele of EBF1 SNP rs2946169 was more frequent in sPTB cases overall than in controls, especially in sporadic sPTB (p = 0.045). Similarly, the CC genotype of ASTN1 SNP rs146756455 was more frequent in sporadic sPTB cases compared to controls (p = 0.019). Finally, the TNF-α SNP rs1800629 minor A allele and AA genotype were more common in the familial sPTB group compared to sporadic sPTB and controls (p < 0.05). The EBF1 SNP rs2963463 polymorphism showed a protective effect in the pathogenesis of sPTB, particularly in women carrying the CC genotype. Moreover, EBF1 SNP rs2946169 and ASTN1 SNP rs146756455, as well as TNF-α SNP rs1800629, were associated with an increased risk of sPTB, representing suggestive potential risk factors for sporadic and familial sPTB, respectively.

Recent Advances in Genomic Studies of Gestational Duration and Preterm Birth

Preterm birth (PTB) is the leading cause of infant mortality and morbidity. For several decades, extensive epidemiologic and genetic studies have highlighted the significant contribution of maternal and offspring genetic factors to PTB. This review discusses the challenges inherent in conventional genomic analyses of PTB and underscores the importance of adopting nonconventional approaches, such as analyzing the mother-child pair as a single analytical unit, to disentangle the intertwined maternal and fetal genetic influences. We elaborate on studies investigating PTB phenotypes through 3 levels of genetic analyses: single-variant, multi-variant, and genome-wide variants.

Systems biology approach: identification of hub genes, signaling pathways, and molecular docking of COL1A1 gene in cervical insufficiency

The collagen type I alpha 1 (COL1A1, OMIM #120,150) gene, encoding the alpha-1 chain of type I collagen (UniProt #P02452), plays a key role in life-homeostasis due to its remarkable involvement in collagen synthesis. It is a promising candidate gene implicated in the pathogenesis of cervical insufficiency (CI). This study aimed to identify genetic variations within the COL1A1 gene that contribute to the development of CI. Polymerase chain reaction (PCR) and amplicon sequencing were implemented for single nucleotide polymorphisms (SNPs) detection (+ 1245G/T, SP1 rs1800012), which revealed wild-type sequence for targeted SNPs in enrolled proband indicated negative results regarding COL1A1 gene involvement for current form of CI. It allows further investigation of other closely connected genes probed in this study. Computational approaches viz. Protein-protein interaction (PPI), gene ontology (GO), and pathway participation were used to identify the crucial hub genes and signaling pathways for COL1A1 and CI. Using the Yet Another Scientific Artificial Reality Application (YASARA) software, molecular docking, and molecular dynamic (MD) simulation with the oxytocin (CID 439,302), estradiol (CID 129,728,744), progesterone (CID 5994) and hydroxyprogesterone (CID 150,788) were done. Interactive bioinformatics analysis demonstrated that the COL1A1 and more than 10 collagen sister genes had a strong connection with CI. In sum, the findings of this study provide insights into a modus operandi that can be utilized to illuminate the path toward studying sister genes and smooth diagnosis of CI. These findings have implications for understanding the foundational process of the condition and potentially developing screening, diagnostic, and therapeutic interventions.

Graphical Abstract

Burden of mental, behavioral, and neurodevelopmental disorders in the Finnish most preterm children: a national register study

Etiologies and the whole picture in childhood mental, behavioral, and neurodevelopmental disorders related to gestational age are unclear. This study included all Finnish children (N = 341,632) born between January 1, 2001, and December 31, 2006, whose data including their mothers (N = 241,284) were collected from national registers. Children with unclear gestational age (GA) (N = 1245), severe congenital malformations (N = 11,746), and moderate/severe/undefined cognitive impairment (N = 1140), and those who died during the perinatal period (N = 599) were excluded. The main outcome was the prevalence of mental and behavioral disorders (International Classification of Disorders) at 0 - 12 years of age in association with GA, adjusted for gender and prenatal variables. Out of all included (N = 326,902) children 16.6% (N = 54,270) were diagnosed to have any mental health disorder at 0 - 12 years. Adjusted Odd Ratio (OR) were for any disorder in preterm (< 37 weeks) 1.37 [1.28 - 1.46] and 4.03 [3.08 - 5.26] in extreme preterm (≤ 28 weeks) versus term born children, p < 0.05. The lower the GA at birth, the higher the risk for multiple disorders and earlier onset of disorder, p < 0.05. Adjusted ORs were for male/female 1.94 [1.90 - 1.99], maternal mental health disorder (yes/not) 1.99 [1.92 - 2.07], and smoking during pregnancy (yes/not) 1.58 [1.54 - 1.62], and these risks were more common in preterm versus term born children (p < 0.05). Extreme early birth was a strong risk factor per se for any or multiple and early shown mental health disorders. Other risk factors for mental health accumulated to preterm children.

Genomic Machine Learning Meta-regression: Insights on Associations of Study Features With Reported Model Performance

Many studies have been conducted with the goal of correctly predicting diagnostic status of a disorder using the combination of genomic data and machine learning. It is often hard to judge which components of a study led to better results and whether better reported results represent a true improvement or an uncorrected bias inflating performance. We extracted information about the methods used and other differentiating features in genomic machine learning models. We used these features in linear regressions predicting model performance. We tested for univariate and multivariate associations as well as interactions between features. Of the models reviewed, 46% used feature selection methods that can lead to data leakage. Across our models, the number of hyperparameter optimizations reported, data leakage due to feature selection, model type, and modeling an autoimmune disorder were significantly associated with an increase in reported model performance. We found a significant, negative interaction between data leakage and training size. Our results suggest that methods susceptible to data leakage are prevalent among genomic machine learning research, resulting in inflated reported performance. Best practice guidelines that promote the avoidance and recognition of data leakage may help the field avoid biased results.

Interferon-stimulated gene 15 polymorphisms are associated with spontaneous preterm birth in Taiwanese women

PROBLEM

Immune and inflammatory responses are known to be major causes of preterm birth (PTB). The maternal genetic background plays an important role in the development of PTB. Interferon-stimulated gene 15 (ISG15) is an interferon-induced protein which can modulate immune cell activation and function. We aim to study if polymorphisms in the ISG15 gene are associated with spontaneous PTB (sPTB) risk in Taiwanese women.

METHOD OF STUDY

ISG15 rs4615788 C/G, rs1921 G/A, and rs8997 A/G polymorphisms were genotyped in a hospital-based study of 112 women with sPTB and 1120 term controls. The plasma concentrations of ISG15 were determined by enzyme-linked immunosorbent assay.

RESULTS

We found the ISG15 rs1921 G-rs8997 A haplotype was associated with decreased risk for PTB (χ2  = 6.26, p = .01, pc  = .04). The A/G genotype of ISG15 rs8997 polymorphism might have the potential to confer reduced risk of PTB women (χ2  = 4.09, p = .04, pc  = .08). Spontaneous PTB women displayed higher plasma ISG15 levels compared to term controls (p < .001). The plasma ISG15 levels among pregnant women with rs8997 A/G genotype were found significantly lower compared to G/G genotype (p = .03).

CONCLUSIONS

Women with the ISG15 rs1921 G-rs8997 A haplotype may associate with spontaneous PTB. These findings provide new insights into the etiology of preterm birth.

The Role of Genetics in Preterm Birth

Preterm birth (PTB), defined as the birth of a child before 37 completed weeks gestation, affects approximately 11% of live births and is the leading cause of death in children under 5 years. PTB is a complex disease with multiple risk factors including genetic variation. Much research has aimed to establish the biological mechanisms underlying PTB often through identification of genetic markers for PTB risk. The objective of this review is to present a comprehensive and updated summary of the published data relating to the field of PTB genetics. A literature search in PubMed was conducted and English studies related to PTB genetics were included. Genetic studies have identified genes within inflammatory, immunological, tissue remodeling, endocrine, metabolic, and vascular pathways that may be involved in PTB. However, a substantial proportion of published data have been largely inconclusive and multiple studies had limited power to detect associations. On the contrary, a few large hypothesis-free approaches have identified and replicated multiple novel variants associated with PTB in different cohorts. Overall, attempts to predict PTB using single "-omics" datasets including genomic, transcriptomic, and epigenomic biomarkers have been mostly unsuccessful and have failed to translate to the clinical setting. Integration of data from multiple "-omics" datasets has yielded the most promising results.

Lack of association between the VEGFA gene polymorphisms and preterm birth in Korean women

Preterm birth (PTB), a pregnancy-related disease, is defined as a birth before 37 weeks of gestation. It is a major cause of maternal mortality and morbidity worldwide, and its incidence rate is steadily increasing. Various genetic factors can contribute to the etiology of PTB. Vascular endothelial growth factor A (VEGFA) gene is an important angiogenic gene and its polymorphisms have been reported to be associated with PTB development. Therefore, we conducted a case-control study to evaluate the association between VEGFA rs699947, rs2010963, and rs3025039 polymorphisms and PTB in Korean women. A total of 271 subjects (116 patients with PTB and 155 women at ≥38 weeks of gestation) were analyzed in this study. The genotyping of VEGFA gene polymorphisms was performed using polymerase chain reaction- restriction fragment length polymorphism. No significant association between the patients with PTB and the control groups was confirmed. In the combination analysis, we found a significant association between PTB and VEGFA rs699947 CC-rs2010963 GG-rs3025039 CC combination (odds ratio, 3.77; 95% confidence interval, 1.091 to 13.032; p = 0.031). The VEGFA rs699947, rs2010963, and rs3025039 polymorphisms might have no genetic association with the pathogenesis of PTB in Korean women. However, the combination analysis indicates the possibility that VEGFA acts in PTB pathophysiology. Therefore, larger sample sets and replication studies are required to further elucidate our findings.

The association between maternal anemia during pregnancy and preterm birth

BACKGROUND & AIMS

Maternal anemia is one of the most serious health problems during pregnancy. The causes of anemia include iron deficiency, parasitic diseases, micronutrient deficiencies, and hereditary hemoglobinopathies. Because the reported association between maternal anemia and preterm labor in different studies is varied depending on the month of pregnancy this study aims to determine this relationship after adjustment for potential confounders.

METHODS

A case-control study was conducted among 801 pregnant women (267 cases and 534 controls) in Sardashat, Iran from October 2012 to October 2013. Hemoglobin (Hb) values were measured for all women participating in the study during the first and second trimesters of pregnancy, and the average Hb values were presented. Statistical analyzes were performed with logistic regression.

RESULTS

The mean age of participants was 26.4 ± 5.25 years for the case group and 27.2 ± 6.51 years for the control group. Preterm birth was associated with maternal anemia during pregnancy [aOR = 2.69 (95% CI; 1.46 to 4.95)] even after adjusting for confounding effects including maternal age, history of abortion [aOR = 2.41 (95% CI; 1.42 to 4.08)], history of preterm birth [aOR = 11.38 (95% CI; 3.48 to 37.22)], obesity (aOR: 3.441; CI95%: 1.18-10.06), parity [aOR = 0.42 (95% CI; 0.25 to 0.69)], preeclampsia/eclampsia [aOR = 6.08 (95% CI; 2.64 to 14)], and GDM [aOR = 4.80 (95% CI; 2.02 to 11.41)]).

CONCLUSION

Early detection and adequate treatment of anemia during pregnancy can help reduce the prevalence of preterm birth.

Genetic variants associated with spontaneous preterm birth in women from India: a prospective cohort study

Background

Despite having the highest number of preterm births globally, no genomic study on preterm birth was previously published from India or other South-Asian countries.

Methods

We conducted a genome-wide association (GWA) study of spontaneous preterm birth (sPTB) on 6211 women from India. We used a novel resampling procedure to identify the associated single nucleotide polymorphisms (SNPs) followed by haplotype association analysis and imputation.

Findings

We found that 512 maternal SNPs were associated with sPTB (p < 2.51e-3), of which minor allele at 19 SNPs (after Bonferroni correction) had increased genotype relative risk. Haplotypes containing six of the 19 SNPs (rs13011430, rs8179838, rs2327290, rs4798499, rs7629800, and rs13180906) were associated with sPTB (p < 9.9e-4; Bonferroni adjusted p-value <0.05). After imputation in regions around the 19 SNPs, 15 imputed SNPs were found to be associated with sPTB (Bonferroni adjusted p-value <0.05). One of these imputed SNPs, rs35760881, and three other SNPs (rs17307697, rs4308815, and rs10983507) were also reported to be associated with sPTB in women belonging to European ancestry. Moreover, we found that GG genotype at rs1152954, one of the associated SNPs, enhanced risk of sPTB and reduced telomere length.

Interpretation

This is the first study from South Asia on the genome-wide identification of maternal SNPs associated with sPTB. These SNPs are known to alter the expression of genes associated with major pathways in sPTB viz. inflammation, apoptosis, cervical ripening, telomere maintenance, selenocysteine biosynthesis, myometrial contraction, and innate immunity. From a public health perspective, the trans-ethnic association of four SNPs identified in our study may help to stratify women with risk of sPTB in most populations.

Funding

Department of Biotechnology (India), Grand Challenges India - All Children Thriving Program and Biotechnology Industry Research Assistance Council (BIRAC).

Paternal and maternal psychiatric history and risk of preterm and early term birth: A nationwide study using Swedish registers

BACKGROUND

Women with psychiatric diagnoses are at increased risk of preterm birth (PTB), with potential life-long impact on offspring health. Less is known about the risk of PTB in offspring of fathers with psychiatric diagnoses, and for couples where both parents were diagnosed. In a nationwide birth cohort, we examined the association between psychiatric history in fathers, mothers, and both parents and gestational age.

METHODS AND FINDINGS

We included all infants live-born to Nordic parents in 1997 to 2016 in Sweden. Psychiatric diagnoses were obtained from the National Patient Register. Data on gestational age were retrieved from the Medical Birth Register. Associations between parental psychiatric history and PTB were quantified by relative risk (RR) and two-sided 95% confidence intervals (CIs) from log-binomial regressions, by psychiatric disorders overall and by diagnostic categories. We extended the analysis beyond PTB by calculating risks over the whole distribution of gestational age, including "early term" (37 to 38 weeks). Among the 1,488,920 infants born throughout the study period, 1,268,507 were born to parents without a psychiatric diagnosis, of whom 73,094 (5.8%) were born preterm. 4,597 of 73,500 (6.3%) infants were born preterm to fathers with a psychiatric diagnosis, 8,917 of 122,611 (7.3%) infants were born preterm to mothers with a pscyhiatric diagnosis, and 2,026 of 24,302 (8.3%) infants were born preterm to both parents with a pscyhiatric diagnosis. We observed a shift towards earlier gestational age in offspring of parents with psychiatric history. The risks of PTB associated with paternal and maternal psychiatric diagnoses were similar for different psychiatric disorders. The risks for PTB were estimated at RR 1.12 (95% CI [1.08, 1.15] p < 0.001) for paternal diagnoses, at RR 1.31 (95% CI [1.28, 1.34] p < 0.001) for maternal diagnoses, and at RR 1.52 (95% CI [1.46, 1.59] p < 0.001) when both parents were diagnosed with any psychiatric disorder, compared to when neither parent had a psychiatric diagnosis. Stress-related disorders were associated with the highest risks of PTB with corresponding RRs estimated at 1.23 (95% CI [1.16, 1.31] p < 0.001) for a psychiatry history in fathers, at 1.47 (95% CI [1.42, 1.53] p < 0.001) for mothers, and at 1.90 (95% CI [1.64, 2.20] p < 0.001) for both parents. The risks for early term were similar to PTB. Co-occurring diagnoses from different diagnostic categories increased risk; for fathers: RR 1.10 (95% CI [1.07, 1.13] p < 0.001), 1.15 (95% CI [1.09, 1.21] p < 0.001), and 1.33 (95% CI [1.23, 1.43] p < 0.001), for diagnoses in 1, 2, and ≥3 categories; for mothers: RR 1.25 (95% CI [1.22, 1.28] p < 0.001), 1.39 (95% CI [1.34, 1.44] p < 0.001) and 1.65 (95% CI [1.56, 1.74] p < 0.001). Despite the large sample size, statistical precision was limited in subgroups, mainly where both parents had specific psychiatric subtypes. Pathophysiology and genetics underlying different psychiatric diagnoses can be heterogeneous.

CONCLUSIONS

Paternal and maternal psychiatric history were associated with a shift to earlier gestational age and increased risk of births before full term. The risk consistently increased when fathers had a positive history of different psychiatric disorders, increased further when mothers were diagnosed and was highest when both parents were diagnosed.

Association between season of conception, month of conception with preterm birth in China: a population-based retrospective cohort study

BACKGROUND

Seasonal patterns of preterm birth were identified in previous studies, but the effect of conception season on preterm birth has not been extensively studied. Based on the notion that the etiological roots of preterm birth lie in the beginning of pregnancy, we did a population-based retrospective cohort study in Southwest China to examine the effects of season of conception and month of conception on preterm birth.

METHODS

We did a population-based retrospective cohort study in women (aged 18-49) who participated in the NFPHEP from 2010 to 2018, and had a singleton livebirth in southwest China. According to the time of the last menstruation reported by the participants, month of conception and season of conception were then ascertained. We used multivariate log-binomial model to adjust the potential risk factors for preterm birth and obtained adjusted risk ratio (aRR) and 95% confidence intervals (95%CI) for conception season, conception month and preterm birth.

RESULTS

Among 194 028 participants, 15 034 women had preterm birth. Compared with pregnancies that were conceived in the summer, pregnancies that were conceived in the spring, autumn and winter had the higher risk of preterm birth (Spring: aRR = 1.10, 95% CI: 1.04-1.15; Autumn: aRR = 1.14, 95% CI: 1.09-1.20; Winter: aRR = 1.28, 95% CI: 1.22-1.34) and also had a higher risk of early preterm birth (Spring: aRR = 1.09, 95% CI: 1.01-1.18; Autumn: aRR = 1.09, 95% CI: 1.01-1.19; Winter: aRR = 1.16, 95% CI: 1.08-1.25). Pregnancies in December, and January had a higher risk of preterm birth and early preterm birth than pregnancies that were conceived in July.

CONCLUSIONS

Our study found that preterm birth was significantly related to season of conception. Preterm and early preterm birth rates were the highest among pregnancies that were conceived in winter, and the lowest among pregnancies in summer.

Newborn metabolomic signatures of maternal per- and polyfluoroalkyl substance exposure and reduced length of gestation

Marginalized populations experience disproportionate rates of preterm birth and early term birth. Exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to reduce length of gestation, but the underlying mechanisms are unknown. In the present study, we characterized the molecular signatures of prenatal PFAS exposure and gestational age at birth outcomes in the newborn dried blood spot metabolome among 267 African American dyads in Atlanta, Georgia between 2016 and 2020. Pregnant people with higher serum perfluorooctanoic acid and perfluorohexane sulfonic acid concentrations had increased odds of an early birth. After false discovery rate correction, the effect of prenatal PFAS exposure on reduced length of gestation was associated with 8 metabolomic pathways and 52 metabolites in newborn dried blood spots, which suggested perturbed tissue neogenesis, neuroendocrine function, and redox homeostasis. These mechanisms explain how prenatal PFAS exposure gives rise to the leading cause of infant death in the United States.

Genetics, epigenetics, and transcriptomics of preterm birth

Preterm birth contributes significantly to neonatal mortality and morbidity. Despite its global significance, there has only been limited progress in preventing preterm birth. Spontaneous preterm birth (sPTB) results from a wide variety of pathological processes. Although many non-genetic risk factors influence the timing of gestation and labor, compelling evidence supports the role of substantial genetic and epigenetic influences and their interactions with the environment contributing to sPTB. To investigate a common and complex disease such as sPTB, various approaches such as genome-wide association studies, whole-exome sequencing, transcriptomics, and integrative approaches combining these with other 'omics studies have been used. However, many of these studies were typically small or focused on a single ethnicity or geographic region with limited data, particularly in populations at high risk for sPTB, or lacked a robust replication. These studies found many genes involved in the inflammation and immunity-related pathways that may affect sPTB. Recent studies also suggest the role of epigenetic modifications of gene expression by the environmental signals as a potential contributor to the risk of sPTB. Future genetic studies of sPTB should continue to consider the contributions of both maternal and fetal genomes as well as their interaction with the environment.

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.

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.

Associations of parental and perinatal factors with subsequent risk of stress-related disorders: a nationwide cohort study with sibling comparison

Little is known about the contribution of pregnancy-related parental and perinatal factors to the development of stress-related disorders. We aimed to investigate whether parental/perinatal adversities entail higher risks of stress-related disorders in the offspring, later in life, by accounting for genetic and early environmental factors. Based on the nationwide Swedish registers, we conducted a population-based cohort study of 3,435,747 singleton births (of which 2,554,235 were full siblings), born 1973-2008 and survived through the age of 5 years. Using both population- and sibling designs, we employed Cox regression to assess the association between parental and perinatal factors with subsequent risk of stress-related disorders. We identified 55,511 individuals diagnosed with stress-related disorders in the population analysis and 37,433 in the sibling analysis. In the population-based analysis we observed increased risks of stress-related disorders among offspring of maternal/paternal age <25, single mothers, parity ≥4, mothers with BMI ≥ 25 or maternal smoking in early pregnancy, gestational diabetes, and offspring born moderately preterm (GA 32-36 weeks), or small-for-gestational-age. These associations were significantly attenuated toward null in the sibling analysis. Cesarean-section was weakly associated with offspring stress-related disorders in population [hazard ratio (HR) 1.09, 95% confidence interval (CI) 1.06-1.12] and sibling analyses (HR 1.10, 95% CI 1.02-1.20). Our findings suggest that most of the observed associations between parental and perinatal factors and risk of stress-related disorders in the population analysis are driven by shared familial environment or genetics, and underscore the importance of family designs in epidemiological studies on the etiology of psychiatric disorders.

Stroke Risks in Adult Survivors of Preterm Birth: National Cohort and Cosibling Study

[Figure: see text].

Spontaneous preterm birth: the underpinnings in the maternal and fetal genomes

Preterm birth (PTB) is a major cause of neonatal mortality and health complications in infants. Elucidation of its genetic underpinnings can lead to improved understanding of the biological mechanisms and boost the development of methods to predict PTB. Although recent genome-based studies of both mother and fetus have identified several genetic loci which might be implicated in PTB, these results suffer from a lack of consistency across multiple studies and populations. Moreover, results of functional validation of most of these findings are unavailable. Since medically indicated preterm deliveries have well-known heterogeneous causes, we have reviewed only those studies which investigated spontaneous preterm birth (sPTB) and have attempted to suggest probable biological mechanisms by which the implicated genetic factors might result in sPTB. We expect our review to provide a panoramic view of the genetics of sPTB.

Familial Contributions to the Association Between Low Birth Weight and Risk of CKD in Adult Life

Introduction

Previous studies have revealed that individuals with low birth weight (LBW) have higher risk of chronic kidney disease (CKD) and that LBW and CKD cluster in families. This study investigates how familial factors affect the association between birth-related risk markers and risk of CKD.

Methods

The Medical Birth Registry (MBR) of Norway has registered all births in Norway since 1967. Sibling data were available through the Norwegian Population Registry. The Norwegian Patient Registry has registered diagnostic codes for all admissions and outpatient visits to Norwegian hospitals since 2008. Data from these registries were linked. Risk of CKD according to whether the individual himself or at least one of his siblings had LBW was analyzed using logistic regression statistics.

Results

Of 1,847,565 individuals, 3336 had been diagnosed with CKD. Compared with individuals without LBW and no siblings with LBW, individuals without LBW but who had a sibling with LBW had adjusted odds ratio (aOR) of 1.33 (1.19–1.49), those with LBW but no siblings with LBW had aOR of 1.74 (1.55–1.95), and those with LBW and a sibling with LBW had aOR of 1.77 (1.54–2.04) for CKD. Similar results were found for LBW for gestational age, but preterm birth revealed weaker associations.

Conclusion

Individuals who have a sibling with LBW have an increased risk of CKD later in life, and individuals who themselves have LBW have an even higher risk. Our findings suggest that there are familial contributions to the nephron endowment in utero hypothesis.

Risk of hypertension into adulthood in persons born prematurely: a national cohort study

AIMS

Preterm birth has been associated with elevated blood pressure early in life; however, hypertension risks from childhood into adulthood remain unclear. We conducted a large population-based study to examine gestational age at birth in relation to hypertension risks from childhood into adulthood.

METHODS AND RESULTS

A national cohort study was conducted of all 4 193 069 singleton live births in Sweden during 1973-2014, who were followed up for hypertension identified from nationwide inpatient and outpatient (specialty and primary care) diagnoses from any health care encounters through 2015 (maximum age 43 years; median 22.5). Cox regression was used to examine gestational age at birth in relation to hypertension risk while adjusting for other perinatal and maternal factors, and co-sibling analyses assessed the potential influence of unmeasured shared familial (genetic and/or environmental) factors. In 86.8 million person-years of follow-up, 62 424 (1.5%) persons were identified with hypertension (median age 29.8 years at diagnosis). Adjusted hazard ratios for new-onset hypertension at ages 18-29 years associated with preterm (<37 weeks) and extremely preterm (22-27 weeks) birth were 1.28 [95% confidence interval (CI), 1.21-1.36] and 2.45 (1.82-3.31), respectively, and at ages 30-43 years were 1.25 (1.18-1.31) and 1.68 (1.12-2.53), respectively, compared with full-term birth (39-41 weeks). These associations affected males and females similarly and appeared substantially related to shared genetic or environmental factors in families.

CONCLUSIONS

In this large national cohort, preterm birth was associated with increased risk of hypertension into early adulthood. Persons born prematurely may need early preventive evaluation and long-term monitoring for the development of hypertension.

The determinant role of IL-6 in the establishment of inflammation leading to spontaneous preterm birth

Preterm birth (PTB) and its consequences are a major public health concern as preterm delivery is the main cause of mortality and morbidity at birth. There are many causes of PTB, but inflammation is undeniably associated with the process of premature childbirth and fetal injury. At present, treatments clinically available mostly involve attempt to arrest contractions (tocolytics) but do not directly address upstream maternal inflammation on development of the fetus. One of the possible solutions may lie in the modulation of inflammatory mediators. Of the many pro-inflammatory cytokines involved in the induction of PTB, IL-6 stands out for its pleiotropic effects and its involvement in both acute and chronic inflammation. Here, we provide a detailed review of the effects of IL-6 on the timing of childbirth, its occurrence during PTB and its indissociable roles with associated fetal tissue damage.

Changes in data management contribute to temporal variation in gestational duration distribution in the Swedish Medical Birth Registry

Multiple factors contribute to gestational duration variability. Understanding the sources of variability allows to design better association studies and assess public health measures. Here, we aimed to assess geographical and temporal changes in the determination of gestational duration and its reporting in Sweden between 1973 and 2012. Singleton live births between 1973 and 2012 were retrieved from the Swedish Medical Birth Register. Gestational duration trends in percentiles and rates of pre- and post-term deliveries were analyzed by plotting the values over time. Temporal changes in gestational duration based on ultrasound and last menstrual period (LMP) estimation methods were compared. Intervals between LMP date and LMP-based due date were analyzed to assess changes in expected gestational duration. In total, 3 940 577 pregnancies were included. From 1973 until 1985, the median of gestational duration estimated based on LMP or ultrasound decreased from 283 to 278 days, and remained stable until 2012. The distribution was relatively stable when ultrasound-based estimates were used. Until the mid-1990s, there was a higher incidence than expected of births occurring on every seventh gestational day from day 157 onward. On an average, these gestational durations were reported 1.8 times more often than adjacent durations. Until 1989, the most common expected gestational duration was 280 days, and thereafter, it was 279 days. The expected gestational duration varied from 279 to 281 days across different Swedish counties. During leap years, the expected gestational duration was one day longer. Consequently, leap years were also associated with significantly higher preterm and lower post-term delivery rates than non-leap years. Changes in data handling and obstetrical practices over the years contribute to gestational duration variation. The resulting increase in variability might reduce precision in association studies and hamper the assessment of public health measures aimed to improve pregnancy outcomes.

Importance of the environment for gestational duration variability and correlation between relatives - results from the Medical Swedish Birth Registry, 1973-2012

It has been suggested that the intergenerational associations in gestational age at delivery are considerably affected by temporal changes in the environmental conditions. We explored whether changing environment affects familial resemblance of gestational age at delivery. Understanding how correlation changes in different settings allows to design better studies aimed to detect genes and environmental factors involved in the parturition process. The Swedish Medical Birth Register was used to retrieve births during 1973–2012. In total, 454,433 parent-child, 2,247,062 full sibling, 405,116 maternal half-sibling and 469,995 paternal half-sibling pairs were identified. A decreasing trend in correlation, associated with increasing age gaps, was observed among all siblings, with the largest drop for full siblings, from ρ = 0.32 (95% confidence interval (CI): 0.31, 0.33) for full siblings with one-year gap to ρ = 0.16 (95% CI: 0.10, 0.22) for full siblings with age gap above 20 years. A variation in association between full siblings born up to two years apart was observed; estimate ρ = 0.28 (95% CI: 0.26, 0.3) in 1973, and ρ = 0.36 (95% CI: 0.33, 0.38) in 2012. Observed variability in the association in gestational age at delivery between the relatives with respect to their birth year or age gap suggests the existence of temporally changing environmental factors.

Postal recruitment for genetic studies of preterm birth: A feasibility study

Background: Preterm birth (PTB) represents the leading cause of neonatal death. Large-scale genetic studies are necessary to determine genetic influences on PTB risk, but prospective cohort studies are expensive and time-consuming. We investigated the feasibility of retrospective recruitment of post-partum women for efficient collection of genetic samples, with self-collected saliva for DNA extraction from themselves and their babies, alongside self-recollection of pregnancy and birth details to phenotype PTB.

Methods: 708 women who had participated in the OPPTIMUM trial (a randomised trial of progesterone pessaries to prevent PTB [ISRCTN14568373]) and consented to further contact were invited to provide self-collected saliva from themselves and their babies. DNA was extracted from Oragene OG-500 (adults) and OG-575 (babies) saliva kits and the yield measured by Qubit. Samples were analysed using a panel of Taqman single nucleotide polymorphism (SNP) assays. A questionnaire designed to meet the minimum data set required for phenotyping PTB was included. Questionnaire responses were transcribed and analysed for concordance with prospective trial data using Cohen’s kappa ( k).

Results: Recruitment rate was 162/708 (23%) for self-collected saliva samples and 157/708 (22%) for questionnaire responses. 161 samples from the mother provided DNA with median yield 59.0µg (0.4-148.9µg). 156 samples were successfully genotyped (96.9%). 136 baby samples had a median yield 11.5µg (0.1-102.7µg); two samples failed DNA extraction. 131 baby samples (96.3%) were successfully genotyped. Concordance between self-recalled birth details and prospective birth details was excellent ( k>0.75) in 4 out of 10 key fields for phenotyping PTB (mode of delivery, labour onset, ethnicity and maternal age at birth).

Conclusion: This feasibility study demonstrates that self-collected DNA samples from mothers and babies were sufficient for genetic analysis but yields were variable. Self-recollection of pregnancy and birth details was inadequate for accurately phenotyping PTB, highlighting the need for alternative strategies for investigating genetic links with PTB.

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.

Utilizing Deep Learning and Genome Wide Association Studies for Epistatic-Driven Preterm Birth Classification in African-American Women

Genome-Wide Association Studies (GWAS) are used to identify statistically significant genetic variants in case-control studies. The main objective is to find single nucleotide polymorphisms (SNPs) that influence a particular phenotype (i.e., disease trait). GWAS typically use a p-value threshold of 5*10^-8 to identify highly ranked SNPs. While this approach has proven useful for detecting disease-susceptible SNPs, evidence has shown that many of these are, in fact, false positives. Consequently, there is some ambiguity about the most suitable threshold for claiming genome-wide significance. Many believe that using lower p-values will allow us to investigate the joint epistatic interactions between SNPs and provide better insights into phenotype expression. One example that uses this approach is multifactor dimensionality reduction (MDR), which identifies combinations of SNPs that interact to influence a particular outcome. However, computational complexity is increased exponentially as a function of higher-order combinations making approaches like MDR difficult to implement. Even so, understanding epistatic interactions in complex diseases is a fundamental component for robust genotype-phenotype mapping. In this paper, we propose a novel framework that combines GWAS quality control and logistic regression with deep learning stacked autoencoders to abstract higher-order SNP interactions from large, complex genotyped data for case-control classification tasks in GWAS analysis. We focus on the challenging problem of classifying preterm births which has a strong genetic component with unexplained heritability reportedly between 20-40 percent. A GWAS data set, obtained from dbGap is utilised, which contains predominantly urban low-income African-American women who had normal and preterm deliveries. Epistatic interactions from original SNP sequences were extracted through a deep learning stacked autoencoder model and used to fine-tune a classifier for discriminating between term and preterm births observations. All models are evaluated using standard binary classifier performance metrics. The findings show that important information pertaining to SNPs and epistasis can be extracted from 4,666 raw SNPs generated using logistic regression (p-value = 5*10^-3) and used to fit a highly accurate classifier model. The following results (Sen = 0.9562, Spec = 0.8780, Gini = 0.9490, Logloss = 0.5901, AUC = 0.9745, and MSE = 0.2010) were obtained using 50 hidden nodes and (Sen = 0.9289, Spec = 0.9591, Gini = 0.9651, Logloss = 0.3080, AUC = 0.9825, and MSE = 0.0942) using 500 hidden nodes. The results were compared with a Support Vector Machine (SVM), a Random Forest (RF), and a Fishers Linear Discriminant Analysis classifier, which all failed to improve on the deep learning approach.

Postal recruitment for genetic studies of preterm birth: A feasibility study

Background: Preterm birth (PTB) represents the leading cause of neonatal death. Large-scale genetic studies are necessary to determine genetic influences on PTB risk, but prospective cohort studies are expensive and time-consuming. We investigated the feasibility of retrospective recruitment of post-partum women for efficient collection of genetic samples, with self-collected saliva for DNA extraction from themselves and their babies, alongside self-recollection of pregnancy and birth details to phenotype PTB. Methods: 708 women who had participated in the OPPTIMUM trial (a randomised trial of progesterone pessaries to prevent PTB [ISRCTN14568373]) and consented to further contact were invited to provide self-collected saliva from themselves and their babies. DNA was extracted from Oragene OG-500 (adults) and OG-575 (babies) saliva kits and the yield measured by Qubit. Samples were analysed using a panel of Taqman single nucleotide polymorphism (SNP) assays. A questionnaire designed to meet the minimum data set required for phenotyping PTB was included. Questionnaire responses were transcribed and analysed for concordance with prospective trial data. Results: Recruitment rate was 162/708 (23%) for self-collected saliva samples and 157/708 (22%) for questionnaire responses. 161 samples from the mother provided DNA with median yield 59.0µg (0.4-148.9µg). 156 samples were successfully genotyped (96.9%). 136 baby samples had a median yield 11.5µg (0.1-102.7µg); two samples failed DNA extraction. 131 baby samples (96.3%) were successfully genotyped. Concordance between self-recalled birth details and prospective birth details ranged from 55 – 99%, median 86%. The highest rates of concordance were found for mode of birth (154/156 [99%]), smoking status (151/157 [96%]) and ethnicity (149/156 [96%]). Conclusion: This feasibility study demonstrates that self-collected DNA samples from mothers and babies were sufficient for genetic analysis but yields were variable. Self-recollection of pregnancy and birth details was inadequate for accurately phenotyping PTB, highlighting the need for alternative strategies for investigating genetic links with PTB.

Keep it in the family: comparing perinatal risks in small-for-gestational-age infants based on population vs within-sibling designs

BACKGROUND

Small-for-gestational-age (SGA) birth is commonly used as a proxy for fetal growth restriction, but also includes constitutionally small infants. Genetic factors account for almost half of the risk of SGA birth. We estimated perinatal risks of SGA birth using both population-based and within-sibling analyses, where the latter by design controls for shared genetic factors and maternal environmental factors that are constant across pregnancies.

METHODS

This was a prospective nationwide cohort study of 2 616 974 singleton infants born in Sweden between January 1987 and December 2012, of whom 1 885 924 were full siblings. We estimated associations between severe or moderate SGA (<3rd percentile and 3rd to <10th percentiles, respectively) and risks of stillbirth, neonatal mortality and morbidity, using both population-based and within-sibling analyses. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated in stillbirth analyses, whereas relative risks (RRs) were used for analyses of neonatal outcomes.

RESULTS

Compared with non-SGA births (>10th percentile), the HR (95% CI) of stillbirth was 18.5 (95% CI 17.4-19.5) among severe SGA births in the population analysis and 22.5 (95% CI 18.7-27.1) in the within-sibling analysis. In non-malformed infants, RRs for neonatal mortality in moderate and severe SGA infants were similarly increased in both population and within-sibling analyses. In term non-malformed infants (≥37 weeks), SGA-related RRs of several neonatal morbidities were higher in within-sibling than in population analyses.

CONCLUSIONS

Perinatal risks associated with fetal growth restriction are more accurately estimated from analyses of SGA in which genetic factors are accounted for.

Recent advances in the genetics of preterm birth

Preterm birth is associated with short- and long-term impairments affecting physical, cognitive, and neuropsychiatric health. These sequelae, together with a rising preterm birth rate and increased survival, make prematurity a growing public health issue because of the increased number of individuals with impaired health throughout the life span. Although a major contribution to preterm birth comes from environmental factors, it is also modestly heritable. Little is known about the architecture of this genetic contribution. Studies of common and of rare genetic variation have had limited power, but recent findings implicate variation in both the maternal and fetal genome. There is some evidence risk alleles in mothers may be enriched for processes related to immunity and inflammation, and in the preterm infant, processes related to brain development. Overall genomic discoveries for preterm birth lag behind progress for many other multifactorial diseases and traits. Investigations focusing on gene-environment interactions may also provide insights, but these studies still have a number of limitations. Adequately sized genetic studies of preterm birth are a priority for the future especially given the breadth of its negative health impacts across the life span and the current interest in newborn genome sequencing.

Transcriptomic and Proteomic Profiling of Human Mesenchymal Stem Cell Derived from Umbilical Cord in the Study of Preterm Birth

OBJECTIVE

Mesenchymal stem cells (MSCs) hold great therapeutic potential in morbidities associated with preterm birth. However, the molecular expressions of MSCs in preterm birth infants are not systematically evaluated. In this study, the dual-omics analyses of umbilical-cord (UC)-derived MSCs to identify the dysregulated cellular functions are presented.

MATERIALS AND METHODS

The UC-MSCs are collected from ten full-term and eight preterm birth infants for microarray and iTRAQ-based proteome profiling.

RESULTS

The integrative analysis of dual-omics data discovered 5615 commonly identified genes/proteins of which 29 genes/proteins show consistent up- or downregulation in preterm birth. The Gene Ontology analysis reveals that dysregulation of mitochondrial translation and cellular response to oxidative stress are mainly enriched in 290 differential expression proteins (DEPs) while the 412 differential expression genes (DEGs) are majorly involved in single-organism biosynthetic process, cellular response to stress, and mitotic cell cycle in preterm birth. Besides, a 13-protein module involving CUL2 and CUL3 is identified, which plays an important role in cullin-RING-based ubiquitin ligase complex, as potential mechanism for preterm birth.

CONCLUSION

The dual-omics data not only provide new insights to the molecular mechanism but also identify panel of candidate markers associated with preterm birth.

Association of preterm birth with lipid disorders in early adulthood: A Swedish cohort study

BACKGROUND

Preterm birth has previously been linked with cardiovascular disease (CVD) in adulthood. However, associations with lipid disorders (e.g., high cholesterol or triglycerides), which are major risk factors for CVD, have seldom been examined and are conflicting. Clinicians will increasingly encounter adult survivors of preterm birth and will need to understand the long-term health sequelae. We conducted the first large population-based study to determine whether preterm birth is associated with an increased risk of lipid disorders.

METHODS AND FINDINGS

A retrospective national cohort study was conducted of all 2,235,012 persons born as singletons in Sweden during 1973 to 1995 (48.6% women), who were followed up for lipid disorders identified from nationwide inpatient, outpatient, and pharmacy data through 2016 (maximum age 44 years). Cox regression was used to adjust for other perinatal and maternal factors, and co-sibling analyses assessed the potential influence of unmeasured shared familial (genetic and/or environmental) factors. A total of 25,050 (1.1%) persons were identified with lipid disorders in 30.3 million person-years of follow-up. Each additional 5 weeks of gestation were associated with a 14% reduction in risk of lipid disorders (adjusted hazard ratio [HR], 0.86; 95% CI, 0.83-0.89; P < 0.001). Relative to full-term birth (gestational age 39-41 weeks), the adjusted HR associated with preterm birth (<37 weeks) was 1.23 (95% CI, 1.16-1.29; P < 0.001), and further stratified was 2.00 (1.41-2.85; P < 0.001) for extremely preterm (22-27 weeks), 1.33 (1.19-1.49; P < 0.001) for very preterm (28-33 weeks), and 1.19 (1.12-1.26; P < 0.001) for late preterm (34-36 weeks). These findings were similar in men and women (e.g., preterm versus full-term, men: HR, 1.22; 95% CI, 1.14-1.31; P < 0.001; women: HR, 1.23; 1.12-1.32; P < 0.001). Co-sibling analyses suggested that they were substantially though not completely explained by shared genetic or environmental factors in families. The main study limitation was the unavailability of laboratory data to assess specific types or severity of lipid disorders.

CONCLUSIONS

In this large national cohort, preterm birth was associated with an increased risk of lipid disorders in early- to midadulthood. Persons born prematurely may need early preventive evaluation and long-term monitoring for lipid disorders to reduce their future cardiovascular risks.

Association of Genetic and Environmental Factors With Autism in a 5-Country Cohort

IMPORTANCE

The origins and development of autism spectrum disorder (ASD) remain unresolved. No individual-level study has provided estimates of additive genetic, maternal, and environmental effects in ASD across several countries.

OBJECTIVE

To estimate the additive genetic, maternal, and environmental effects in ASD.

DESIGN, SETTING, AND PARTICIPANTS

Population-based, multinational cohort study including full birth cohorts of children from Denmark, Finland, Sweden, Israel, and Western Australia born between January 1, 1998, and December 31, 2011, and followed up to age 16 years. Data were analyzed from September 23, 2016 through February 4, 2018.

MAIN OUTCOMES AND MEASURES

Across 5 countries, models were fitted to estimate variance components describing the total variance in risk for ASD occurrence owing to additive genetics, maternal, and shared and nonshared environmental effects.

RESULTS

The analytic sample included 2 001 631 individuals, of whom 1 027 546 (51.3%) were male. Among the entire sample, 22 156 were diagnosed with ASD. The median (95% CI) ASD heritability was 80.8% (73.2%-85.5%) for country-specific point estimates, ranging from 50.9% (25.1%-75.6%) (Finland) to 86.8% (69.8%-100.0%) (Israel). For the Nordic countries combined, heritability estimates ranged from 81.2% (73.9%-85.3%) to 82.7% (79.1%-86.0%). Maternal effect was estimated to range from 0.4% to 1.6%. Estimates of genetic, maternal, and environmental effects for autistic disorder were similar with ASD.

CONCLUSIONS AND RELEVANCE

Based on population data from 5 countries, the heritability of ASD was estimated to be approximately 80%, indicating that the variation in ASD occurrence in the population is mostly owing to inherited genetic influences, with no support for contribution from maternal effects. The results suggest possible modest differences in the sources of ASD risk between countries.

Revisiting the association between maternal and offspring preterm birth using a sibling design

Background

Previous studies have reported an intergenerational association between maternal and offspring preterm birth (PTB) but the nature of the association remains unclear. We assessed the association between maternal and offspring preterm birth using a quasi-experimental sibling design and distinguishing between preterm birth types.

Methods

We conducted a retrospective intergenerational cohort study of 39,573 women born singleton in Manitoba, Canada (1980–2002) who gave birth to 79,198 singleton infants (1995–2016). To account for familial confounding we defined a subcohort of 1033 sisters with discordant PTB status who subsequently gave birth and compared offspring PTB rates between 2499 differentially exposed cousins using log-binomial fixed-effects generalized estimating equation models. PTB was defined as a delivery < 37 gestation weeks, divided into spontaneous and provider-initiated.

Results

In the population cohort, mothers born preterm were more likely to give birth preterm [Adjusted Relative Risk (ARR): 1.39; 95% Confidence Interval (CI): 1.25, 1.54] and very preterm birth [ARR: 1.76; 95% CI: 1.29, 2.41]. However, in the siblings cohort, the intergenerational association was not apparent among births to sisters with discordant PTB status [ARR: 1.02; 95% CI: 0.77, 1.34 for preterm birth and ARR: 0.88; 95% CI: 0.38, 2.02 for very preterm birth]. Mothers born at term with a sister born preterm had a similarly elevated risk of delivering a preterm infant (10%) than their preterm sisters. Intergenerational patterns were observed for spontaneous PTB but not for provider-initiated PTB.

Conclusions

Our findings suggest that it is not the fact of having been born preterm that puts women at higher risk of delivering preterm, but the fact of having been born to a mother who ever delivered preterm. Consideration of a female family history of PTB may better identify women at higher risk of preterm delivery than relying on maternal preterm birth status alone. Further research may benefit from distinguishing preterm birth types.

Association of a placental Interleukin-6 genetic variant (rs1800796) with DNA methylation, gene expression and risk of acute chorioamnionitis

BACKGROUND

Acute chorioamnionitis (aCA), inflammation of the placenta and fetal membranes, is a frequently reported lesion in preterm deliveries. Genetic variants in innate immune system genes such as Interleukin-6 (IL6) may contribute to the placenta's inflammatory response, thus predisposing some pregnancies to aCA. These genetic variants may modulate molecular processes such as DNA methylation and gene expression, and in turn might affect susceptibility to aCA. Currently, there is remarkably little research on the role of fetal (placental) genetic variation in aCA. We aimed to explore the associations between genetic variants in candidate immune-system genes and susceptibility towards inflammatory responses in the placenta, which is linked to a strong inflammatory response in the newborn.

METHODS

DNA samples from 269 placentas (72 aCA cases, 197 non-aCA cases) were collected for this study. Samples were genotyped at 55 ancestry informative markers (AIMs) and 16 additional single nucleotide polymorphisms (SNPs) in 12 candidate innate immune system genes using the Sequenom iPLEX Gold Assay. Publicly available datasets were used to obtain DNA methylation (GSE100197, GSE74738, GSE115508, GSE44667, GSE98224) and gene expression data (GSE44711, GSE98224).

RESULTS

Differences in IL6 placental allele frequencies were associated with aCA (rs1800796, p = 0.04) with the CC genotype specifically implicated (OR = 3.1; p = 0.02). In a subset of the placental samples (n = 67; chorionic villi), we showed that the IL6 SNP (rs1800796) was associated with differential DNA methylation in five IL6-related CpG sites (cg01770232, cg02335517, cg07998387, cg13104385, and cg0526589), where individuals with a CC genotype showed higher DNA methylation levels than individuals carrying the GG genotype. Using two publicly available datasets, we observed that the DNA methylation levels at cg01770232 negatively correlated with IL6 gene expression in the placenta (r = - 0.67, p < 0.004; r = - 0.56, p < 2.937e-05).

CONCLUSIONS

We demonstrated that the minor C allele at the IL6 SNP (rs1800796), which is largely limited to East Asian populations, is associated with the presence of aCA. This SNP was associated with increased DNA methylation at a nearby MEPC2 binding site, which was also associated with decreased expression of IL6 in the placenta. Decreased expression of IL6 may increase vulnerability to microbial infection. Additional studies are required to confirm this association in Asian populations with larger sample sizes.

Assessing the risk factors before pregnancy of preterm births in Iran: a population-based case-control study

Background

Preterm birth is a major cause of prenatal and postnatal mortality particularly in developing countries. This study investigated the maternal risk factors associated with the risk of preterm birth.

Methods

A population-based case-control study was conducted in several provinces of Iran on 2463 mothers referred to health care centers. Appropriate descriptive and analytical statistical methods were used to evaluate the association between maternal risk factors and the risk of preterm birth. All tests were two-sided, and P values < 0.05 were considered to be statistically significant.

Results

The mean gestational age was 31.5 ± 4.03 vs. 38.8 ± 1.06 weeks in the case and control groups, respectively. Multivariate regression analysis showed a statistically significant association between preterm birth and mother’s age and ethnicity. Women of Balooch ethnicity and age ≥ 35 years were significantly more likely to develop preterm birth (OR: 1.64; 95% CI: 1.01–-2.44 and OR: 9.72; 95% CI: 3.07–30.78, respectively). However, no statistically significant association was observed between preterm birth and mother’s place of residence, level of education, past history of cesarean section, and BMI.

Conclusion

Despite technological advances in the health care system, preterm birth still remains a major concern for health officials. Providing appropriate perinatal health care services as well as raising the awareness of pregnant women, especially for high-risk groups, can reduce the proportion of preventable preterm births.

A case control study of risk factors and neonatal outcomes of preterm birth

OBJECTIVE

The aim is to examine risk factors and neonatal outcomes of preterm birth and to provide basis in preventing preterm birth.

MATERIALS AND METHODS

we carried out our study on 1328 term controls and 1328 preterm birth cases. By using multivariable logistic regression procedures we estimated odds ratio (OR) of potential preterm birth risk factors. T-test and chi-square test were used to estimate differences between groups.

RESULTS

Maternal age, prior history of pregnancy and abortion, prenatal care, complications of pregnancy (includes hypertension, intrahepatic cholestasis of pregnancy (ICP), fetal growth restriction (FGR), premature rupture of the membranes (PROM), placenta previa, abnormal presentation, abnormal S/D ratio et al.) were significantly associated with preterm birth. Several factors emerged as being statistically significant risk factors for preterm birth, such as prior history of pregnancy, hypertension, ICP, FGR, PROM, placenta previa and abnormal presentation. The time of prenatal care was shown to be a protective factor. Additionally, we observed evidence suggested that male babies are known to have a significant higher risk of preterm birth than female babies.

CONCLUSION

Prior history of pregnancy, hypertension, ICP, FGR, PROM, placenta previa and abnormal presentation were covariates identified in this study as risk factors for preterm birth. Preterm birth is an important reason of neonatal poor prognosis and death.

Investigating fetal growth restriction and perinatal risks in appropriate for gestational age infants: using cohort and within-sibling analyses

OBJECTIVE

Fetal growth restriction refers to fetuses that fail to reach their growth potential. Studies within siblings may be useful to disclose fetal growth restriction in appropriate for gestational age (AGA) infants. We analysed associations between birthweight percentiles and perinatal risks in AGA infants, using both population-based and within-sibling analyses.

DESIGN

Population-based cohort study.

SETTING AND SAMPLE

Using nation-wide Swedish registries (1987-2012), we identified 2 134 924 singleton AGA births (10th-90th birthweight percentile for gestational age), of whom 1 377 326 were full siblings.

METHODS

Unconditional Poisson regression was used for population analyses, and conditional (matched) Poisson regression for within-sibling analyses. We estimated associations between birthweight percentiles and stillbirth, neonatal mortality, and morbidity, using incidence rate ratios (IRRs) with 95% confidence intervals (CIs).

RESULTS

Stillbirth and neonatal mortality risks declined with increasing birthweight percentiles, but the declines were larger in within-sibling analyses. Compared with the reference group (40th to <60th percentile), IRRs (95% CIs) of stillbirth for the lowest and highest percentile groups (10th to <25th and 75th-90th percentiles, respectively) were 1.87 (1.72-2.03) to 0.76 (0.68-0.85) in population analysis and 2.60 (2.27-2.98) and 0.43 (0.36-0.50) in within-sibling analysis. Neonatal morbidity risks in term non-malformed infants with low birthweight percentiles were generally only increased in within-sibling analyses.

CONCLUSION

Using birthweight information from siblings may help to define fetal growth restriction in AGA infants.

TWEETABLE ABSTRACT

Size of siblings helps to detect growth-restricted infants with seemingly normal birthweights.

Out-of-Home Care and Subsequent Preterm Delivery: An Intergenerational Cohort Study

OBJECTIVES

Adverse early-life experience may affect preterm delivery later in life through priming of stress response. We aim to investigate the links between out-of-home care (OHC) experience in childhood, as a proxy of severe adversities, on subsequent risk of preterm delivery.

METHODS

A register-based national cohort of all women born in Sweden between 1973 and 1977 (N = 175 821) was crosslinked with information on these women's subsequent deliveries as recorded in the Swedish medical birth register. During 1986-2012, 343 828 livebirths of these women were identified. The associations between women's OHC experience and her risk of preterm delivery were analyzed through logistic regression models, adjusting for women's own preterm birth, intrauterine growth, and childhood socioeconomic situation.

RESULTS

Compared with women that never entered OHC, women with OHC experience up to and after age 10 were both associated with increased risks of preterm delivery (adjusted odds ratio [aOR] = 1.23 [95% confidence interval 1.08-1.40] and aOR = 1.29 [1.13-1.48], respectively). Women who experienced OHC before or at 10 years of age had increased risk of both spontaneous and medically indicated preterm delivery (aOR = 1.19 [1.03-1.38] and aOR = 1.27 [1.02-1.59], respectively). Women who experienced OHC after age 10 had a more pronounced risk of medically indicated preterm delivery (aOR = 1.76 [1.44-2.16]) than for spontaneous preterm delivery (aOR = 1.08 [0.92-1.27]).

CONCLUSIONS

Women who were placed in OHC in childhood had increased risk of preterm delivery independent from their own perinatal history. Stress response, as 1 consequence of early life adversities, may take its toll on women's reproductive health and their offspring, calling for integrative efforts in preventing early life adversity.

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.

Gestational age at birth and academic performance: population-based cohort study

Background

Numerous studies suggest pre-term birth is associated with cognitive deficit. However, less is known about cognitive outcomes following post-term birth, or the influence of weight variations within term or post-term populations. We examined associations between gestational age (GA) and school performance, by weight-for-GA, focusing on extremely pre- and post-term births.

Method

Record linkage study of Swedish children born 1973-94 ( n =  2 008 102) with a nested sibling comparison ( n =  439 629). We used restricted cubic regression splines to examine associations between GA and the grade achieved on leaving secondary education, comparing siblings to allow stronger causal inference with regard to associations between GA and school performance.

Results

Grade averages of both pre- and post-term children were below those of full-term counterparts and lower for those born small-for-GA. The adjusted grades of extremely pre-term children (at 24 completed weeks), while improving in later study periods, were lower by 0.43 standard deviations (95% confidence interval 0.38-0.49), corresponding with a 21-point reduction (19 to 24) on a 240-point scale. Reductions for extremely post-term children (at 45 completed weeks) were lesser [-0.15 standard deviation (-0.17 to -0.13) or -8 points (-9 to -7)]. Among matched siblings, we observed weaker residual effects of pre-term and post-term GA on school performance.

Conclusions

There may be independent effects of fetal maturation and fetal growth on school performance. Associations among matched siblings, although attenuated, remained consistent with causal effects of pre- and post-term birth on school performance.

Heritable Variation, With Little or No Maternal Effect, Accounts for Recurrence Risk to Autism Spectrum Disorder in Sweden

BACKGROUND

Autism spectrum disorder (ASD) has both genetic and environmental origins, including potentially maternal effects. Maternal effects describe the association of one or more maternal phenotypes with liability to ASD in progeny that are independent of maternally transmitted risk alleles. While maternal effects could play an important role, consistent with association to maternal traits such as immune status, no study has estimated maternal, additive genetic, and environmental effects in ASD.

METHODS

Using a population-based sample consisting of all children born in Sweden from 1998 to 2007 and their relatives, we fitted statistical models to family data to estimate the variance in ASD liability originating from maternal, additive genetic, and shared environmental effects. We calculated sibling and cousin family recurrence risk ratio as a direct measure of familial, genetic, and environmental risk factors and repeated the calculations on diagnostic subgroups, specifically autistic disorder (AD) and spectrum disorder (SD), which included Asperger's syndrome and/or pervasive developmental disorder not otherwise specified.

RESULTS

The sample consisted of 776,212 children of whom 11,231 had a diagnosis of ASD: 4554 with AD, 6677 with SD. We found support for large additive genetic contribution to liability; heritability (95% confidence interval [CI]) was estimated to 84.8% (95% CI: 73.1-87.3) for ASD, 79.6% (95% CI: 61.2-85.1) for AD, and 76.4% (95% CI: 63.0-82.5) for SD.

CONCLUSIONS

There was modest, if any, contribution of maternal effects to liability for ASD, including subtypes AD and SD, and there was no support for shared environmental effects. These results show liability to ASD arises largely from additive genetic variation.

Divergent Patterns of Mitochondrial and Nuclear Ancestry Are Associated with the Risk for Preterm Birth

OBJECTIVE

To examine linkages between mitochondrial genetics and preterm birth by assessing the risk for preterm birth associated with the inheritance of nuclear haplotypes that are ancestrally distinct from mitochondrial haplogroup.

STUDY DESIGN

Genome-wide genotyping studies of cohorts of preterm and term individuals were evaluated. We determined the mitochondrial haplogroup and nuclear ancestry for individuals and developed a scoring for the degree to which mitochondrial ancestry is divergent from nuclear ancestry.

RESULTS

Infants with higher degrees of divergent mitochondrial ancestry were at increased risk for preterm birth (0.124 for preterm vs 0.105 for term infants; P< .05). This finding was validated in 1 of 2 replication cohorts. We also observed that greater degrees of divergent ancestry correlated with earlier delivery within the primary study population, but this finding was not replicated in secondary cohorts born preterm.

CONCLUSIONS

Individuals with divergent patterns of mitochondrial and nuclear ancestry are at increased risk for preterm birth. These findings may in part explain the higher rates of preterm birth in African Americans and in individuals with a matrilineal family history of preterm birth.

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.

Polymorphism of the ADRB2 Rs1042713 Gene is not Associated with Spontaneous Preterm Birth: Analyses in a Slovenian Sample and Meta Analysis

The β-2-adrenergic receptor (ADRB2) gene has an important impact on smooth muscle relaxation, including the smooth muscles of the uterus. The results of previously published studies of the association between the ADRB2 rs1042713 polymorphism and spontaneous preterm birth (SPTB) were inconsistent. We evaluated the association between ADRB2 and SPTB in a case-control association study in a Slovenian sample population and performed a meta analysis of previously published studies. No association was found between the polymorphism in the ADRB2 gene and SPTB in the Slovenian sample of 98 SPTB patients and 135 controls under dominant [χ² = 0.01, p = 0.92, odds ratio (OR) = 1.03, 95% confidence interval (95% CI) = 0.52-2.04), recessive (χ² = 0.01, p = 0.92, OR = 0.98, 95% CI = 0.57-1.70) and codominant genetic models (χ² = 0.01, p = 0.92, OR = 0.99, 95% CI = 0.59-1.68). The meta analysis of a pooled sample of 404 SPTB patients and 878 controls suggested no association of ADRB2 polymorphism and SPTB under dominant (OR = 1.12, 95% CI = 0.81-1.54) and recessive genetic models (OR = 0.84, 95% CI = 0.64-1.12). These findings suggest no association between the ADRB2 rs1042713 gene polymorphism and SPTB. Further association studies with larger sample sizes are needed.

The Role of Body, Mind, and Environment in Preterm Birth: Mind the Gap

Preterm birth continues to be a problem affecting low-, middle-, and high-income countries, with rates increasing in some areas despite ongoing efforts to reduce the incidence. This emphasizes the need for more effective interventions, particularly if we aim to achieve the broad health targets of the Sustainable Development Goals (SDGs) by 2030. The current focus on medically-oriented interventions such as reducing nonmedically-indicated induction of labor, cesarean birth, and multiple embryo transfers associated with assisted reproductive technologies, as well as the application of cervical cerclage and use of progesterone therapy, though important, are likely only partial solutions to the complex phenomenon of preterm birth. Preterm birth has multiple etiologies. The biologic mechanisms involved in preterm labor and how it may be triggered are not well understood. There is growing evidence to suggest some of these triggers may also be related to stress and environmental conditions. In this review, we focus on evidence concerning psychosocial (mind) and environmental factors (environment) as well as briefly review the evidence related to maternal and fetal factors (body) associated with the risk of preterm birth, with reference to some of the SDGs. We also assess emerging evidence regarding the interaction of the body, mind, and environment in relation to preterm birth, currently a gap in our knowledge, and how these interactions could impact clinical practice. Findings suggest that multidisciplinary expertise and approaches will be needed to develop effective interventions to address the complex etiologies of preterm birth, as opposed to single-risk-factor mitigation. Clinicians and researchers will play key roles in identifying many of these risk factors and shaping interventions that address this complex issue. Addressing the interlinkages between body, mind, and environment through the integration of research and clinical practice is critical to reducing the risk of preterm birth and contributing to the achievement of the SDGs.

Mutations in fetal genes involved in innate immunity and host defense against microbes increase risk of preterm premature rupture of membranes (PPROM)

BACKGROUND

Twin studies have revealed a significant contribution of the fetal genome to risk of preterm birth. Preterm premature rupture of membranes (PPROM) is the leading identifiable cause of preterm delivery. Infection and inflammation of the fetal membranes is commonly found associated with PPROM.

METHODS

We carried out whole exome sequencing (WES) of genomic DNA from neonates born of African-American mothers whose pregnancies were complicated by PPROM (76) or were normal term pregnancies (N = 43) to identify mutations in 35 candidate genes involved in innate immunity and host defenses against microbes. Targeted genotyping of mutations in the candidates discovered by WES was conducted on an additional 188 PPROM cases and 175 controls.

RESULTS

We identified rare heterozygous nonsense and frameshift mutations in several of the candidate genes, including CARD6, CARD8, DEFB1, FUT2, MBL2, NLP10, NLRP12, and NOD2. We discovered that some mutations (CARD6, DEFB1, FUT2, MBL2, NLRP10, NOD2) were present only in PPROM cases.

CONCLUSIONS

We conclude that rare damaging mutations in innate immunity and host defense genes, the majority being heterozygous, are more frequent in neonates born of pregnancies complicated by PPROM. These findings suggest that the risk of preterm birth in African-Americans may be conferred by mutations in multiple genes encoding proteins involved in dampening the innate immune response or protecting the host against microbial infection and microbial products.

The inherited risk of retained placenta: a population based cohort study

OBJECTIVE

To investigate whether retained placenta in the first generation is associated with an increased risk of retained placenta in the second generation.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

Using linked generational data from the Swedish Medical Birth Register 1973-2012, we identified 494 000 second-generation births with information on the birth of the mother (first-generation index birth). For 292 897 of these births there was information also on the birth of the father.

METHODS

Risk of retained placenta in the second generation was calculated as adjusted odds ratios (aOR) by unconditional logistic regression with 95% confidence intervals (95% CI) according to whether retained placenta occurred in a first generation birth or not.

MAIN OUTCOME

Retained placenta in the second generation.

RESULTS

The risk of retained placenta in a second-generation birth was increased if retained placenta had occurred at the mother's own birth (aOR 1.66, 95% CI 1.52-1.82), at the birth of one of her siblings (aOR 1.58, 95% CI 1.43-1.76) or both (aOR 2.75, 95% CI 2.18-3.46). The risk was slightly increased if retained placenta had occurred at the birth of the father (aOR 1.23, 95% CI 1.07-1.41). For preterm births in both generations, the risk of retained placenta in the second generation was increased six-fold if retained placenta had occurred at the mother's birth (OR 6.55, 95% CI 2.68-16.02).

CONCLUSION

There is an intergenerational recurrence of retained placenta on the maternal and most likely also on the paternal side. The recurrence risk seems strongest in preterm pregnancies.

TWEETABLE ABSTRACT

A population-based cohort study suggests that there is an intergenerational recurrence of retained placenta.

Transgenerational Transmission of Preterm Birth Risk: The Role of Race and Generational Socio-Economic Neighborhood Context

Objectives We investigated associations of mothers' preterm birth (PTB) status with her infants' PTB risk. We also examined whether this relationship differs by mothers' race and generational socio-economic neighborhood context. Methods Participants were 6592 non-Hispanic (NH) white and NH black mother-infant pairs born in 2009-2011 and 1979-1998, respectively, in Allegheny County, Pennsylvania. Birth records were used to determine gestational age at birth, PTB status (<37 completed weeks of gestation), and PTB subgroups-late and early PTB (34-36 weeks and <34 completed weeks of gestation, respectively). Census data on tract racial composition and household income were used to characterize residential race and economic environment. Logistic regression models were used to calculate Odds Ratios (ORs), Relative Risk Ratios (RRR), and 95% confidence intervals (CIs). Stratified analyses were conducted to assess effect modification. Results Overall, 8.21, 6.63 and 1.58% infants had PTB, LPTB, and EPTB, respectively. Maternal PTB status was associated with a 46% increase in infant PTB (95% CI: 1.08-1.98), EPTB (95% CI: 0.80-2.69), and LPTB (95% CI: 1.04-2.04) risk. Maternal PTB-infant PTB associations, particularly maternal PTB-infant LPTB associations, were stronger among NH blacks, mothers in neighborhoods with a high percentage of NH black residents in both generations, or mothers who moved to neighborhoods with a higher percentage of NH black residents. Conclusions for Practice Race and generational socio-economic neighborhood context modify transgenerational transmission of PTB risk. These findings are important for identification of at-risk populations and to inform future mechanistic studies.