Cumulative lifetime maternal stress and epigenome-wide placental DNA methylation in the PRISM cohort

Prenatal exposure to air pollution and BWGA Z-score: Modifying effects of placenta leukocyte telomere length and infant sex

BACKGROUND

Air pollutants, such as fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3), have been associated with adverse birth outcomes, including low birth weight, often exhibiting sex-specific effects. However, the modifying effect of placental telomere length (TL), reflecting cumulative lifetime oxidative stress in mothers, remains unexplored.

METHOD

Using data from a Northeastern U.S. birth cohort (n = 306), we employed linear regression and weighted quantile sum models to assess trimester-average air pollution exposures and birth weight for gestational age (BWGA) z-scores. Placental TL, categorized by median split, was considered as an effect modifier. Interactions among air pollutants, placental TL, infant sex, and BWGA z-score were evaluated.

RESULTS

Without placental TL as a modifier, only 1st trimester O3 was significantly associated with BWGA z-scores (coefficient: 0.33, 95% CI: 0.03, 0.63). In models considering TL interactions, a significant modifying effect was observed between 3rd trimester NO2 and BWGA z-scores (interaction p-value = 0.02). Specifically, a one interquartile range (1-IQR) increase in 3rd trimester NO2 was linked to a 0.28 (95% CI: 0.06, 0.52) change in BWGA z-score among shorter placental TL group, with no significant association among longer TL group. Among male infants, there were significant associations between 3rd trimester PM2.5 exposure and BWGA z-scores in the longer TL group (coefficient: -0.34, 95% CI: -0.61, -0.02), and between 1st trimester O3 exposure and BWGA z-scores among males in the shorter TL group (coefficient: 0.59, 95% CI: 0.06, 1.08). For females, only a negative association in 2nd trimester mixture model was observed within the longer TL group (coefficient: -0.10, 95% CI: -0.21, -0.01).

CONCLUSION

These findings highlight the need to consider the complex interactions among prenatal air pollutant exposures, placental TL, and fetal sex to better elucidate those at greatest risk for adverse birth outcomes.

Epigenetics of prenatal stress in humans: the current research landscape

Fetal exposure to prenatal stress can have significant consequences on short- and long-term health. Epigenetic mechanisms, especially DNA methylation (DNAm), are a possible process how these adverse environmental events could be biologically embedded. We evaluated candidate gene as well as epigenome-wide association studies associating prenatal stress and DNAm changes in peripheral tissues; however, most of these findings lack robust replication. Prenatal stress-associated epigenetic changes have also been linked to child health including internalizing problems, neurobehavioral outcomes and stress reactivity. Future studies should focus on refined measurement and definition of prenatal stress and its timing, ideally also incorporating genomic as well as longitudinal information. This will provide further opportunities to enhance our understanding of the biological embedding of prenatal stress exposure.

Maternal steroids during pregnancy and their associations with exposure to lifetime stressful life events, prenatal stress appraisal and psychological functioning

BACKGROUND

During pregnancy, steroids enable physiological adaptations in response to many factors, including maternal stress or psychological functioning. While stress and psychological dysfunction can have endocrine-disrupting effects beyond cortisol disruption, associations between prenatal maternal stress or related psychological dysfunction and the broader steroid milieu remain understudied.

AIM

To assess associations between independent and joint maternal stress and psychological functioning measures and steroid profiles in pregnancy (22-40 gestational weeks) in the Programming of Intergenerational Stress Mechanisms (PRISM) birth cohort (n = 334).

METHODS

Serum metabolomics detected 42 steroids and their metabolites, which were grouped into five classes (pregnenolone, androgens, estrogens, progestin, and corticosteroids). The Perceived Stress Scale, Life Stressor Checklist-Revised, and Edinburgh Postnatal Depression Scale indexed lifetime traumatic/non-traumatic stressors, global prenatal stress appraisal, and depressive symptoms during pregnancy, respectively. Exposures were categorized as high-low using the corresponding 3rd quartiles. We assessed associations between both individual and joint stress exposures with steroid classes using linear mixed effect models and with individual steroids using linear regressions. We also examined fetal sex-specific effects.

RESULTS

High prenatal perceived stress was independently associated with lower levels of androgens and estrogens in the overall sample [β (95%CI): androgens: -0.13 (-0.25;-0.01); estrogens: -0.16 (-0.31;-0.01)], particularly among women carrying males [androgens: -0.22 (-0.39;-0.05); estrogens: -0.28 (-0.50;-0.07)]. Results on estrogens were consistent when considering joint exposure to both greater lifetime stressors and higher prenatal perceived stress. We also found a single testosterone metabolite-5alpha-androstan-3alpha,17alpha-diol disulfate-negatively associated with both individual high perceived stress and joint exposure to high lifetime stressors and high perceived stress among women carrying males.

CONCLUSIONS

Increased maternal perceived stress experienced in pregnancy was independently associated with lower maternal androgen and estrogen levels during pregnancy in the overall sample, particularly among women carrying males. Results on estrogens were consistent when we considered the joint exposure of increased lifetime stressors and higher prenatal perceived stress.

Epigenome-wide meta-analysis of prenatal maternal stressful life events and newborn DNA methylation

Prenatal maternal stressful life events are associated with adverse neurodevelopmental outcomes in offspring. Biological mechanisms underlying these associations are largely unknown, but DNA methylation likely plays a role. This meta-analysis included twelve non-overlapping cohorts from ten independent longitudinal studies (N = 5,496) within the international Pregnancy and Childhood Epigenetics consortium to examine maternal stressful life events during pregnancy and DNA methylation in cord blood. Children whose mothers reported higher levels of cumulative maternal stressful life events during pregnancy exhibited differential methylation of cg26579032 in ALKBH3. Stressor-specific domains of conflict with family/friends, abuse (physical, sexual, and emotional), and death of a close friend/relative were also associated with differential methylation of CpGs in APTX, MyD88, and both UHRF1 and SDCCAG8, respectively; these genes are implicated in neurodegeneration, immune and cellular functions, regulation of global methylation levels, metabolism, and schizophrenia risk. Thus, differences in DNA methylation at these loci may provide novel insights into potential mechanisms of neurodevelopment in offspring.

Maternal adverse childhood experiences (ACEs) and DNA methylation of newborns in cord blood

BACKGROUND

Adverse childhood experiences (ACEs) increase the risk of poor health outcomes later in life. Psychosocial stressors may also have intergenerational health effects by which parental ACEs are associated with mental and physical health of children. Epigenetic programming may be one mechanism linking parental ACEs to child health. This study aimed to investigate epigenome-wide associations of maternal preconception ACEs with DNA methylation patterns of children. In the Center for the Health Assessment of Mothers and Children of Salinas study, cord blood DNA methylation was measured using the Illumina HumanMethylation450 BeadChip. Preconception ACEs, which occurred during the mothers' childhoods, were collected using a standard ACE questionnaire including 10 ACE indicators. Maternal ACE exposures were defined in this study as (1) the total number of ACEs; (2) the total number of ACEs categorized as 0, 1-3, and > 4; and (3) individual ACEs. Associations of ACE exposures with differential methylated positions, regions, and CpG modules determined using weighted gene co-expression network analysis were evaluated adjusting for covariates.

RESULTS

Data on maternal ACEs and cord blood DNA methylation were available for 196 mother/newborn pairs. One differential methylated position was associated with maternal experience of emotional abuse (cg05486260/FAM135B gene; q value < 0.05). Five differential methylated regions were significantly associated with the total number of ACEs, and 36 unique differential methylated regions were associated with individual ACEs (Šidák p value < 0.05). Fifteen CpG modules were significantly correlated with the total number of ACEs or individual ACEs, of which 8 remained significant in fully adjusted models (p value < 0.05). Significant modules were enriched for pathways related to neurological and immune development and function.

CONCLUSIONS

Maternal ACEs prior to conception were associated with cord blood DNA methylation of offspring at birth. Although there was limited overlap between differential methylated regions and CpGs in modules associated with ACE exposures, statistically significant regions and networks were related to genes involved in neurological and immune function. Findings may provide insights to pathways linking psychosocial stressors to health. Further research is needed to understand the relationship between changes in DNA methylation and child health.

DNA methylation and 28-year cardiovascular disease risk in type 1 diabetes: the Epidemiology of Diabetes Complications (EDC) cohort study

BACKGROUND

The potential for DNA methylation (DNAm) as an early marker for cardiovascular disease (CVD) and how such an association might differ by glycemic exposure has not been examined in type 1 diabetes, a population at increased CVD risk. We thus performed a prospective epigenome-wide association study of blood leukocyte DNAm (EPIC array) and time to CVD incidence over 28 years in a childhood-onset (< 17 years) type 1 diabetes cohort, the Pittsburgh Epidemiology of Diabetes Complications (EDC) study (n = 368 with DNA and no CVD at baseline), both overall and separately by glycemic exposure, as measured by HbA1c at baseline (split at the median: < 8.9% and ≥ 8.9%). We also assessed whether DNAm-CVD associations were independent of established cardiometabolic risk factors, including body mass index, estimated glucose disposal rate, cholesterol, triglycerides, blood pressure, pulse rate, albumin excretion rate, and estimated glomerular filtration rate.

RESULTS

CVD (first instance of CVD death, myocardial infarction, coronary revascularization, ischemic ECG, angina, or stroke) developed in 172 participants (46.7%) over 28 years. Overall, in Cox regression models for time to CVD, none of the 683,597 CpGs examined reached significance at a false discovery rate (FDR) ≤ 0.05. In participants with HbA1c < 8.9% (n = 180), again none reached FDR ≤ 0.05, but three were associated at the a priori nominal significance level FDR ≤ 0.10: cg07147033 in MIB2, cg12324048 (intergenic, chromosome 3), and cg15883830 (intergenic, chromosome 1). In participants with HbA1c ≥ 8.9% (n = 188), two CpGs in loci involved in calcium channel activity were significantly associated with CVD (FDR ≤ 0.05): cg21823999 in GPM6A and cg23621817 in CHRNA9; four additional CpGs were nominally associated (FDR ≤ 0.10). In participants with HbA1c ≥ 8.9%, DNAm-CVD associations were only modestly attenuated after cardiometabolic risk factor adjustment, while attenuation was greater in those with HbA1c < 8.9%. No pathways were enriched in those with HbA1c < 8.9%, while pathways for calcium channel activity and integral component of synaptic membrane were significantly enriched in those with HbA1c ≥ 8.9%.

CONCLUSIONS

These results provide novel evidence that DNAm at loci involved in calcium channel activity and development may contribute to long-term CVD risk beyond known risk factors in type 1 diabetes, particularly in individuals with greater glycemic exposure, warranting further study.

Influence of maternal psychological distress during COVID-19 pandemic on placental morphometry and texture

The Coronavirus Disease 2019 (COVID-19) pandemic has been accompanied by increased prenatal maternal distress (PMD). PMD is associated with adverse pregnancy outcomes which may be mediated by the placenta. However, the potential impact of the pandemic on in vivo placental development remains unknown. To examine the impact of the pandemic and PMD on in vivo structural placental development using advanced magnetic resonance imaging (MRI), acquired anatomic images of the placenta from 63 pregnant women without known COVID-19 exposure during the pandemic and 165 pre-pandemic controls. Measures of placental morphometry and texture were extracted. PMD was determined from validated questionnaires. Generalized estimating equations were utilized to compare differences in PMD placental features between COVID-era and pre-pandemic cohorts. Maternal stress and depression scores were significantly higher in the pandemic cohort. Placental volume, thickness, gray level kurtosis, skewness and run length non-uniformity were increased in the pandemic cohort, while placental elongation, mean gray level and long run emphasis were decreased. PMD was a mediator of the association between pandemic status and placental features. Altered in vivo placental structure during the pandemic suggests an underappreciated link between disturbances in maternal environment and perturbed placental development. The long-term impact on offspring is currently under investigation.

Association of Parental Cardiovascular Health With Disability-Adjusted Life Years in the Offspring: Results From the Framingham Heart Study

BACKGROUND

Disability-adjusted life years (DALYs) are used to evaluate the relative burden of diseases in populations to help set prevention or treatment priorities. The impact of parental cardiovascular health (CVH) on healthy life years lost from cardiovascular disease (CVD) in adult offspring is unknown. We compared parent-offspring CVD DALYs trends over the life course and examined the association of parental CVH with offspring CVD DALYs.

METHODS

Using data from the Framingham Heart Study, 4814 offspring-mother-father trios were matched for age at selected baseline exams. CVH score was computed from the number of CVH metrics attained at recommended levels: poor (0-2), intermediate (3-4), and ideal (5-7). CVD DALYs were defined as the sum of years of life lost and years lived with CVD. Age-sex-standardized life expectancy and disability weights were derived from the actuarial life tables and Global Burden of Disease study, respectively. Multivariable-adjusted linear regression was used to investigate the association of parental CVH with offspring CVD DALYs.

RESULTS

Over an equal 47-year follow-up, parents lost nearly twice the number of CVD DALYs compared to their offspring (23 234 versus 12 217). However, age-adjusted CVD DALYs were higher at younger ages and similar along the life course for parents and offspring. One-unit increase in parental CVH was associated with 5 healthy life months saved in offspring. Offspring of mothers with ideal versus poor CVH had 3 healthy life years saved (β=-3.0 DALYs [95% CI, -5.6 to -0.3]). No statistically significant association was found between paternal CVH categories and offspring CVD DALYs.

CONCLUSIONS

Higher maternal and paternal CVH were associated with increased healthy life years in offspring; however, the association was strongest between mothers and offspring. Investment in CVH promotion along the life course has the potential to reduce the burden of CVD in the current and future generation of adults.

Epigenetics as a Biomarker for Early-Life Environmental Exposure

PURPOSE OF REVIEW

There is interest in evaluating the developmental origins of health and disease (DOHaD) which emphasizes the role of prenatal and early-life environments on non-communicable health outcomes throughout the life course. The ability to rigorously assess and identify early-life risk factors for later health outcomes, including those with childhood onset, in large population samples is often limited due to measurement challenges such as impractical costs associated with prospective studies with a long follow-up duration, short half-lives for some environmental toxicants, and lack of biomarkers that capture inter-individual differences in biologic response to external environments.

RECENT FINDINGS

Epigenomic patterns, and DNA methylation in particular, have emerged as a potential objective biomarker to address some of these study design and exposure measurement challenges. In this article, we summarize the literature to date on epigenetic changes associated with specific prenatal and early-life exposure domains as well as exposure mixtures in human observational studies and their biomarker potential. Additionally, we highlight evidence for other types of epigenetic patterns to serve as exposure biomarkers. Evidence strongly supports epigenomic biomarkers of exposure that are detectable across the lifespan and across a range of exposure domains. Current and future areas of research in this field seek to expand these lines of evidence to other environmental exposures, to determine their specificity, and to develop predictive algorithms and methylation scores that can be used to evaluate early-life risk factors for health outcomes across the life span.

Toxicoepigenetics and Environmental Health: Challenges and Opportunities

The rapidly growing field of toxicoepigenetics seeks to understand how toxicant exposures interact with the epigenome to influence disease risk. Toxicoepigenetics is a promising field of environmental health research, as integrating epigenetics into the field of toxicology will enable a more thorough evaluation of toxicant-induced disease mechanisms as well as the elucidation of the role of the epigenome as a biomarker of exposure and disease and possible mediator of exposure effects. Likewise, toxicoepigenetics will enhance our knowledge of how environmental exposures, lifestyle factors, and diet interact to influence health. Ultimately, an understanding of how the environment impacts the epigenome to cause disease may inform risk assessment, permit noninvasive biomonitoring, and provide potential opportunities for therapeutic intervention. However, the translation of research from this exciting field into benefits for human and animal health presents several challenges and opportunities. Here, we describe four significant areas in which we see opportunity to transform the field and improve human health by reducing the disease burden caused by environmental exposures. These include (1) research into the mechanistic role for epigenetic change in environment-induced disease, (2) understanding key factors influencing vulnerability to the adverse effects of environmental exposures, (3) identifying appropriate biomarkers of environmental exposures and their associated diseases, and (4) determining whether the adverse effects of environment on the epigenome and human health are reversible through pharmacologic, dietary, or behavioral interventions. We then highlight several initiatives currently underway to address these challenges.

Associations between antenatal maternal asthma status and placental DNA methylation

INTRODUCTION

Maternal asthma in pregnancy is associated with adverse perinatal and child health outcomes; however, mechanisms are poorly understood.

METHODS

The PRogramming of Intergenerational Stress Mechanisms (PRISM) prospective pregnancy cohort characterized asthma history during pregnancy via questionnaires and quantified placental DNAm using the Illumina Infinium HumanMethylation450 BeadChip. We performed epigenome-wide association analyses (n = 223) to estimate associations between maternal active or inactive asthma, as compared to never asthma, and placental differentially methylated positions (DMPs) and differentially variable positions (DVPs). Models adjusted for maternal pre-pregnancy body mass index, smoking status, parity, age and education level and child sex. P-values were FDR-adjusted.

RESULTS

One hundred and fifty-nine (71.3%) pregnant women reported no history of asthma (never asthma), 15 (6.7%) reported inactive, and 49 (22%) reported active antenatal asthma. Women predominantly self-identified as Black/Hispanic Black [88 (39.5%)] and Hispanic/non-Black [42 (18.8%)]. We identified 10 probes at FDR<0.05 and 4 probes at FDR<0.10 characterized by higher variability in maternal active asthma compared to never asthma mapping to GPX3, LHPP, PECAM1, ATAD3C, and ARHGEF4 and 2 probes characterized by lower variation mapping to CHMP4A and C5orf24. Amongst women with inactive asthma, we identified 52 probes, 41 at FDR<0.05 and an additional 11 at FDR <0.10, with higher variability compared to never asthma; BMP4, LHPP, PHYHIPL, and ZSCAN23 were associated with multiple DVPs. No associations were observed with DMPs.

DISCUSSION

We observed alterations in placental DNAm in women with antenatal asthma, as compared to women without a history of asthma. Further research is needed to understand the impact on fetal development.

Gestational exposure to neighborhood police-reported crime and early childhood blood pressure in Durham, NC

Gestational exposure to police-reported crime is associated with adverse birth outcomes, but no previous research has evaluated the effects of gestational crime exposure on early childhood health or attempted to disentangle the health effects of neighborhood crime from the effects of neighborhood policing. Using data from 672 Newborn Epigenetics Study participants, we evaluate the effects of gestational exposure to violent crime and racialized drug policing on early childhood blood pressure. We demonstrate that violence and drug policing are consistently associated with increased blood pressure among children born to Black participants but not White or Latinx participants.

Understanding Health Inequalities Through the Lens of Social Epigenetics

Longstanding racial/ethnic inequalities in morbidity and mortality persist in the United States. Although the determinants of health inequalities are complex, social and structural factors produced by inequitable and racialized systems are recognized as contributing sources. Social epigenetics is an emerging area of research that aims to uncover biological pathways through which social experiences affect health outcomes. A growing body of literature links adverse social exposures to epigenetic mechanisms, namely DNA methylation, offering a plausible pathway through which health inequalities may arise. This review provides an overview of social epigenetics and highlights existing literature linking social exposures—i.e., psychosocial stressors, racism, discrimination, socioeconomic position, and neighborhood social environment—to DNA methylation in humans.We conclude with a discussion of social epigenetics as a mechanistic link to health inequalities and provide suggestions for future social epigenetics research on health inequalities.

Association Between Maternal Adverse Childhood Experiences and Neonatal SCG5 DNA Methylation-Effect Modification by Prenatal Home Visiting

Maternal childhood adversity and trauma may elicit biological changes that impact the next generation through epigenetic responses measured in DNA methylation (DNAm). These epigenetic associations could be modified by the early postnatal environment through protective factors, such as early childhood home visiting (HV) programs that aim to mitigate deleterious intergenerational effects of adversity. In a cohort of 53 mother-child pairs recruited in 2015-2016 for the Pregnancy and Infant Development Study (Cincinnati, Ohio), we examined the association between maternal adverse childhood experiences (ACEs) and neonatal DNAm in the secretogranin V gene (SCG5), which is important in neuroendocrine function. We examined prenatal HV as an effect modifier. Mothers completed a questionnaire on ACEs during pregnancy, and infant buccal samples were collected 1 month postpartum. Multivariable linear regression was used to examine the association between maternal ACEs and neonatal DNAm expressed as M-values averaged across 4 cytosine-phosphate-guanine dinucleotide sites. A higher number of maternal ACEs (>3) was associated with a 5.79-percentage-point lower offspring DNAm (95% confidence interval: -10.44, -1.14), and the association was modified by the number of home visits received during pregnancy. In a population of at-risk mother-child dyads, preliminary evidence suggests that maternal ACEs have a relationship with offspring SCG5 DNAm that differs by the amount of prenatal HV.

Periconception and Prenatal Exposure to Maternal Perceived Stress and Cord Blood DNA Methylation

BACKGROUND

Maternal prenatal stress is associated with physiologic and adverse mental health outcomes in the offspring, but the underlying biologic mechanisms are unknown. We examined the associations of maternal perceived stress, including preconception exposure, with DNA methylation (DNAm) alterations in the cord blood buffy coats of 358 singleton infants.

METHODS

Maternal perceived stress was measured prior to and throughout pregnancy in a cohort of women enrolled in Effects of Aspirin in Gestation and Reproduction Trial (EAGeR) trial. Perceived stress assessments based on a standardized Likert-scale were obtained in periconception (~2 months preconception and 2-8 weeks of gestation) and pregnancy (8-36 weeks of gestation). Cumulative perceived stress was estimated by calculating the predicted area under the curve of stress reported prior to and during pregnancy. DNAm was measured by the Infinium MethylationEPIC BeadChip. Multivariable robust linear regression was used to assess associations of perceived stress with individual CpG probes.

RESULTS

Based on a 0 to 3 scale, average reported preconception and early pregnancy stress were 0.76 (0.60) and 0.67 (0.50), respectively. Average mid- to late-pregnancy stress, based on a 0 to 10 scale, was 4.9 (1.6). Neither periconception nor pregnancy perceived stress were associated with individual CpG sites in neonatal cord blood (all false discovery rate [FDR] >5%).

CONCLUSION

No effects of maternal perceived stress exposure on array-wide cord blood neonatal methylation differences were found.

Prenatal particulate matter exposure and mitochondrial mutational load at the maternal-fetal interface: Effect modification by genetic ancestry

Prenatal ambient particulate matter (PM2.5) exposure impacts infant development and alters placental mitochondrial DNA abundance. We investigated whether the timing of PM2.5 exposure predicts placental mitochondrial mutational load using NextGen sequencing in 283 multi-ethnic mother-infant dyads. We observed increased PM2.5exposure, particularly during mid- to late-pregnancy and among genes coding for NADH dehydrogenase and subunits of ATP synthase, was associated with a greater amount of nonsynonymous mutations. The strongest associations were observed for participants of African ancestry. Further work is needed to tease out the role of mitochondrial genetics and its impact on offspring development and emerging disease disparities.

Associations between infant sex and DNA methylation across umbilical cord blood, artery, and placenta samples

DNA methylation (DNAm) is vulnerable to dysregulation by environmental exposures during epigenetic reprogramming that occurs in embryogenesis. Sexual dimorphism in environmentally induced DNAm dysregulation has been identified and therefore it is important to understand sex-specific DNAm patterns. DNAm at several autosomal sites has been consistently associated with sex in cord blood and placental foetal tissues. However, there is limited research comparing sex-specific DNAm across tissues, particularly differentially methylated regions (DMRs). This study leverages DNAm data measured using the Illumina HumanMethylation450 BeadChip in cord blood (N = 179), placenta (N = 229), and umbilical artery samples (N = 229) in the PRogramming of Intergenerational Stress Mechanisms (PRISM) cohort to identify autosomal DMRs and differentially methylated positions (DMPs). A replication analyses was conducted in an independent cohort (GEO Accession GSE129841). We identified 183, 257, and 419 DMRs and 2119, 2281, and 3405 DMPs (p_Bonferroni < 0.05) in cord blood, placenta, and artery samples, respectively. Thirty-nine DMRs overlapped in all three tissues, overlapping with genes involved in spermatogenesis (NKAPL, PIWIL2 and AURKC) and X-inactivation (LRIF1). In replication analysis, 85% of DMRs overlapped with those identified in PRISM. Overall, DMRs and DMPs had higher methylation levels among females in cord blood and artery samples, but higher methylation levels among males in placenta samples. Further research is necessary to understand biological mechanisms that contribute to differences in sex-specific DNAm signatures across tissues, as well as to determine if sexual dimorphism in the epigenome impacts response to environmental stressors.

Genetic and in utero environmental contributions to DNA methylation variation in placenta

Genetic and prenatal environmental factors shape fetal development and cardiometabolic health in later life. A key target of genetic and prenatal environmental factors is the epigenome of the placenta, an organ that is implicated in fetal growth and diseases in later life. This study had two aims: (1) to identify and functionally characterize placental variably methylated regions (VMRs), which are regions in the epigenome with high inter-individual methylation variability; and (2) to investigate the contributions of fetal genetic loci and 12 prenatal environmental factors (maternal cardiometabolic-,psychosocial-, demographic- and obstetric-related) on methylation at each VMR. Akaike's information criterion was used to select the best model out of four models [prenatal environment only, genotype only, additive effect of genotype and prenatal environment (G + E), and their interaction effect (G × E)]. We identified 5850 VMRs in placenta. Methylation at 70% of VMRs was best explained by G × E, followed by genotype only (17.7%), and G + E (12.3%). Prenatal environment alone best explained only 0.03% of VMRs. We observed that 95.4% of G × E models and 93.9% of G + E models included maternal age, parity, delivery mode, maternal depression or gestational weight gain. VMR methylation sites and their regulatory genetic variants were enriched (P < 0.05) for genomic regions that have known links with regulatory functions and complex traits. This study provided a genome-wide catalog of VMRs in placenta and highlighted that variation in placental DNA methylation at loci with regulatory and trait relevance is best elucidated by integrating genetic and prenatal environmental factors, and rarely by environmental factors alone.

Placental mitochondrial DNA mutational load and perinatal outcomes: Findings from a multi-ethnic pregnancy cohort

Mitochondria fuel placental activity, with mitochondrial dysfunction implicated in several perinatal complications. We investigated placental mtDNA mutational load using NextGen sequencing in relation to birthweight and gestational length among 358 mother-newborn pairs. We found that higher heteroplasmy, especially in the hypervariable displacement loop region, was associated with shorter gestational length. Results were similar among male and female pregnancies, but stronger in magnitude among females. With regard to growth, we observed that higher mutational load was associated with lower birthweight-for-gestational age (BWGA) among females, but higher BWGA among males. These findings support potential sex-differential fetal biological strategies for coping with increased heteroplasmies.

A cross-cohort analysis of autosomal DNA methylation sex differences in the term placenta

BACKGROUND

Human placental DNA methylation (DNAme) data is a valuable resource for studying sex differences during gestation, as DNAme profiles after delivery reflect the cumulative effects of gene expression patterns and exposures across gestation. Here, we present an analysis of sex differences in autosomal DNAme in the uncomplicated term placenta (n = 343) using the Illumina 450K array.

RESULTS

At a false discovery rate < 0.05 and a mean sex difference in DNAme beta value of > 0.10, we identified 162 autosomal CpG sites that were differentially methylated by sex and replicated in an independent cohort of samples (n = 293). Several of these differentially methylated CpG sites were part of larger correlated regions of sex differential DNAme. Although global DNAme levels did not differ by sex, the majority of significantly differentially methylated CpGs were more highly methylated in male placentae, the opposite of what is seen in differential methylation analyses of somatic tissues. Patterns of autosomal DNAme at these 162 CpGs were significantly associated with maternal age (in males) and newborn birthweight standard deviation (in females).

CONCLUSIONS

Our results provide a comprehensive analysis of sex differences in autosomal DNAme in the term human placenta. We report a list of high-confidence autosomal sex-associated differentially methylated CpGs and identify several key features of these loci that suggest their relevance to sex differences observed in normative and complicated pregnancies.

Maternal Cardiovascular Health and Adverse Childbirth Outcomes in the United States: Analysis of the Pregnancy Risk Assessment Monitoring System

BACKGROUND

Cardiovascular-related adverse childbirth outcomes have been increasing in the United States, with widening racial and ethnic disparities.

OBJECTIVE

We examined the association between maternal cardiovascular health (CVH) and childbirth outcomes among US births.

METHODS

We analyzed data from the Pregnancy Risk Assessment Monitoring System. Ideal CVH was defined as a composite of 4 cardiovascular disease (CVD) risk factors: absence of a medical diagnosis of diabetes, hypertension, history of cigarette smoking before or during pregnancy, and a pre-pregnancy body mass index of 18.5 to 24.9 kg/m2. Childbirth outcomes examined were preterm birth, low birthweight, and mode of birth. Survey logistic regression was used for multivariate analyses.

RESULTS

A total of 34 918 women were included in our study, and most (61%) had more than 1 CVD risk factor. Clustering of CVD risk factors was more likely among women with an annual income of less than $40 000 and not college educated and found among non-Hispanic Black, Hispanic, and American Indian/Alaska Natives (P < .001). The odds of an adverse childbirth outcome increased with each additional CVD risk factor. Hypertension was highest among non-Hispanic Black women (20%) and the strongest predictor of having a low-birth-weight infant (odds ratio [OR], 3.16; 95% confidence interval [CI], 2.86-3.48), preterm birth (OR, 2.72; 95% CI, 2.40-3.07), and cesarean birth (OR, 1.68; 95% CI, 1.52-1.87).

CONCLUSION

Clustering of maternal CVD risk factors was significantly associated with adverse childbirth outcomes. Unfavorable CVH and its association with adverse childbirth outcomes were most common in women of color, calling for special attention to this group.

Associations Between Maternal Lifetime Stress and Placental Mitochondrial DNA Mutations in an Urban Multiethnic Cohort

BACKGROUND

Disrupted placental functioning due to stress can have lifelong implications. Cumulative stress and trauma are likely to have lasting impacts on maternal physiological functioning and offspring development, resulting in increased risk for later-life complex disorders for which racial disparities exist.

METHODS

This study examined the association between maternal lifetime stress and placental mitochondrial DNA mutational load in an urban multiethnic cohort. Maternal lifetime exposure to stressful events was assessed using the validated Life Stressor Checklist-Revised. Whole mitochondrial DNA sequencing was performed and mutations were determined for 365 placenta samples with complete exposure and covariate data. Multivariable regression was used to model maternal lifetime stress in relation to placental mitochondrial DNA mutational load. Racial/ethnic differences were examined by cross-product terms and contrast statements. Gene-wise analyses were conducted.

RESULTS

We identified 13,189 heteroplasmies (Phred score > 10,000, minor allele frequency < 0.5, number of mutant reads > 1). Women experiencing increased psychosocial stress over their lifetime exhibited a higher number of total placental mitochondrial mutations (β = .23, 95% confidence interval = .03 to .42) and heteroplasmic mutations (β = .18, 95% confidence interval = .05 to .31) but not homoplasmic mutations (β = -.008, 95% confidence interval = -.03 to .01); the strongest associations were observed among Black women and genes coding for NADH dehydrogenase and cytochrome c oxidase subunits.

CONCLUSIONS

Cumulative maternal lifetime stress is associated with a greater mitochondrial mutational load, particularly among Black women. The impact of racial/ethnic differences in mutational load on placental function directly affecting offspring development and/or leading to chronic disease disparities warrants further investigation.

Understanding Racial Disparities of Preterm Birth Through the Placenta

The racial disparity associated with preterm birth is a public health concern in the United States. The placenta is the principal metabolic, respiratory, and endocrine organ of the fetus and a key route by which environmental exposures are transmitted from mother to offspring. Available at every delivery, it may serve as a marker of differences in prenatal exposures that manifest differently by race. Recently, we described differences in placental pathology between African-American and White preterm births: the prevalence of chronic inflammation was higher among African-American women's placentas compared with those of White women. Similarly, racial differences have been shown in placental malperfusion and placental weight. Social determinants such as poverty and stress from discrimination have been implicated in racial disparities in preterm birth. To date, however, the underlying biological mechanisms, whether through inflammatory, oxidative stress, or other pathways involving epigenetic programming, remain largely unknown. The placenta, complemented by maternal and umbilical cord blood biomarkers, may provide important information on the perinatal environment that explains the origins of racial disparities in preterm birth rates and subsequent health outcomes. This article reviews existing literature and current research gaps. Opportunities are discussed for future placental research that may reveal novel mechanisms leading to the development of new approaches in the prevention and management of preterm birth and its outcomes.

Gaining a deeper understanding of social determinants of preterm birth by integrating multi-omics data

In the US, high rates of preterm birth (PTB) and profound Black-White disparities in PTB have persisted for decades. This review focuses on the role of social determinants of health (SDH), with an emphasis on maternal stress, in PTB disparity and biological embedding. It covers: (1) PTB disparity in US Black women and possible contributors; (2) the role of SDH, highlighting maternal stress, in the persistent racial disparity of PTB; (3) epigenetics at the interface between genes and environment; (4) the role of the genome in modifying maternal stress-PTB associations; (5) recent advances in multi-omics studies of PTB; and (6) future perspectives on integrating multi-omics with SDH to elucidate the Black-White disparity in PTB. Available studies have indicated that neither environmental exposures nor genetics alone can adequately explain the Black-White PTB disparity. Preliminary yet promising findings of epigenetic and gene-environment interaction studies underscore the value of integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women. In an era of rapid advancements in biomedical sciences and technologies and a growing number of prospective birth cohort studies, we have unprecedented opportunities to advance this field and finally address the long history of health disparities in PTB. IMPACT: This review provides an overview of social determinants of health (SDH) with a focus on maternal stress and its role on Black-White disparity in preterm birth (PTB). It summarizes the available literature on the interplay of maternal stress with key biological layers (e.g., individual genome and epigenome in response to environmental stressors) and significant knowledge gaps. It offers perspectives that such knowledge may provide deeper insight into how SDH affects PTB and why some women are more vulnerable than others and underscores the critical need for integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women.

Abnormal placental DNA methylation variation in spontaneous preterm birth

OBJECTIVE

Preterm birth (PTB) has become a major public health concern as the leading cause of neonatal death, but little is understood about its etiology. Children born preterm are also at increased risk of long-term consequences such as neurodevelopmental disorders, adulthood hypertension and diabetes. Recent studies have indicated that DNA methylation may be involved in the occurrence of PTB as well as related adverse outcomes. The latest Infinium EPIC BeadChip extends the coverage of the genome and provides a better tool to help investigate the involvement of DNA methylation in these conditions.

METHODS

We conducted this case-control study in three Women and Children's hospitals in South China, and enrolled 32 spontaneous preterm births and 16 term births. We assessed placental DNA methylation profiling of these participants with the Infinium EPIC BeadChip. We identified PTB and gestational age (GA)-associated CpG sites with limma regression model, and applied seqlm to identify PTB-associated regions. We performed gene ontology analysis to further interpret functional enrichment of the identified differentially methylated genes in PTB.

RESULTS

We identified a total of 8 differentially methylated positions (DMPs) that were significantly associated with PTB (FDR < 0.1) and a total of 15 DMPs that were associated with GA (FDR < 0.1). In the regional analysis, one differentially methylated region in the SLC23A1 gene overlapped with PTB-associated CpG site. The differentially methylated CpG sites in PTB were mapped to the genes involving in biological processes mainly regarding neurodevelopment, regulation of inflammation and metabolism.

CONCLUSION

Our findings suggested that preterm placenta have distinct DNA methylation alterations, and these alteration patterns established at birth provide insight into the long-term consequences of preterm birth.

Developmental origins of metabolic diseases

Almost 2 billion adults in the world are overweight, and more than half of them are classified as obese, while nearly one-third of children globally experience poor growth and development. Given the vast amount of knowledge that has been gleaned from decades of research on growth and development, a number of questions remain as to why the world is now in the midst of a global epidemic of obesity accompanied by the "double burden of malnutrition," where overweight coexists with underweight and micronutrient deficiencies. This challenge to the human condition can be attributed to nutritional and environmental exposures during pregnancy that may program a fetus to have a higher risk of chronic diseases in adulthood. To explore this concept, frequently called the developmental origins of health and disease (DOHaD), this review considers a host of factors and physiological mechanisms that drive a fetus or child toward a higher risk of obesity, fatty liver disease, hypertension, and/or type 2 diabetes (T2D). To that end, this review explores the epidemiology of DOHaD with discussions focused on adaptations to human energetics, placental development, dysmetabolism, and key environmental exposures that act to promote chronic diseases in adulthood. These areas are complementary and additive in understanding how providing the best conditions for optimal growth can create the best possible conditions for lifelong health. Moreover, understanding both physiological as well as epigenetic and molecular mechanisms for DOHaD is vital to most fully address the global issues of obesity and other chronic diseases.

Association between prenatal immune phenotyping and cord blood leukocyte telomere length in the PRISM pregnancy cohort

BACKGROUND

Environmental exposures including air pollutants, toxic metals, and psychosocial stress have been associated with shorter telomere length (TL) in newborns. These exposures have in turn been linked to an enhanced inflammatory immune response. Increased inflammation during pregnancy may be a central biological pathway linking environmental factors with reduced TL at birth. Approaches that more comprehensively characterize the prenatal inflammatory milieu rather than targeting specific individual cytokines in relation to newborn TL may better elucidate inflammatory mechanisms.

METHODS

Analyses included 129 mother-child dyads enrolled in the PRogramming of Intergenerational Stress Mechanisms (PRISM) pregnancy cohort. We measured 92 inflammation related proteins during pregnancy in maternal serum using the Olink protein array and quantified cord blood relative leukocyte TL (rLTL) via qPCR. We leveraged a tree-based machine learning algorithm to select the most important inflammatory related proteins jointly associated with rLTL. We then evaluated the combined association between the selected proteins with rLTL using Bayesian Weighted Quantile Sum (BWQS) Regression. Analyses were adjusted for gestational week of serum collection, maternal race/ethnicity, age, and education, and fetal sex. We evaluated major biological function of the identified proteins by using the UniProtKB, a centralized repository of curated functional information.

RESULTS

Three proteins were negatively and linearly associated with rLTL (CASP8 β: -0.22 p = 0.008, BNGF β: -0.43 p = 0.033, TRANCE β: 0.38 p = 0.004). Results from BWQS regression showed a significant overall decrease in rLTL (β: -0.26 95%CrI: -0.43, -0.07) per quartile increase of the mixture, with CASP8 contributing the greatest weight (CASP8 50%; BNGF 27%, and TRANCE 23%). The identified proteins were involved in the regulation of apoptotic processes and cell proliferation.

CONCLUSIONS

This proteomics approach identifies novel maternal prenatal inflammatory protein biomarkers associated with shortened rLTL in newborns.

Neurophysiology of cognitive behavioural therapy, deep breathing and progressive muscle relaxation used in conjunction with ART treatments: a narrative review

BACKGROUND

Infertility is defined as the failure to achieve clinical pregnancy after 12 months of regular unprotected intercourse. It could be due to male or female factors, each requiring different treatment options. ART treatment exposes couples to numerous psychological stressors. Therefore, it has been recommended by the ESHRE Psychology and Counselling Guideline Development Group recently that psychosocial support should be offered as a complementary therapy during infertility treatments. In this context, the efficiency of different psychological interventions, such as cognitive behaviour therapy (CBT), deep breathing (DB), and progressive muscle relaxation (PMR), was evaluated in several clinical trials in terms of couples' mental health and pregnancy outcomes.

OBJECTIVE AND RATIONALE

The neurophysiology of CBT, DB and PMR, which are used in interventional studies, in both men and women undergoing ART, has not yet been fully elucidated. This review represents a comprehensive report, aiming to collate novel insights into the neurobiological processes and physiological mechanisms that occur during the practice of CBT, DB and PMR.

SEARCH METHODS

PubMed, Google Scholar and Cochrane Library were interrogated to conduct this comprehensive literature review. The search was carried out using combinations of MeSH terms and keywords: infertility, assisted reproductive techniques, IVF, ICSI, emotions, psychological stress, cognitive behavioural therapy, mind-body therapies and relaxation. Relevant information related to the mechanism of action of stress management techniques were obtained from original articles and reviews published in English without taking into consideration the time of publication. Moreover, as it was not the major focus of the review, only recent systematic reviews (2015-2019) pinpointing the effects of psychological interventions on infertility treatment outcomes were also retrieved from the above-mentioned databases.

OUTCOMES

CBT, DB and PMR may modify the activity of stress-related brain regions such as the prefrontal cortex, amygdala, hypothalamus and hippocampus, as demonstrated by functional MRI and electroencephalogram studies. Furthermore, applying these techniques was associated with mood improvements and a decline in stress biomarkers, and, hypothetically, reducing stress biomarkers attenuates the stress-induced effects on ART outcomes.

WIDER IMPLICATIONS

Increasing the knowledge of fertility staff, researchers and physicians regarding the mechanisms of action of these stress management techniques has several advantages. For instance, understanding the underlying neurophysiological pathways would assist practitioners to engage ART couples in the practice of these techniques. Also, it may enhance the quality of the support programmes and psychological research. Accordingly, this will ensure that these interventions reach their full potential and therefore improve clinical outcomes.

Parental cardiovascular health predicts time to onset of cardiovascular disease in offspring

BACKGROUND

Cardiovascular disease (CVD) risk factors are transmitted from parents to children. We prospectively examined the association between parental cardiovascular health (CVH) and time to onset of CVD in the offspring.

METHODS AND RESULTS

The study consisted of a total of 5967 offspring-mother-father trios derived from the Framingham Heart Study. Cardiovascular health score was defined using the seven American Heart Association's CVH metrics attained at ideal levels: poor (0-2), intermediate (3-4), and ideal CVH (5-7). Multivariable-adjusted Cox proportional hazards regression models, Kaplan-Meier plots, and Irwin's restricted mean were used to examine the association and sex-specific differences between parental CVH and offspring's CVD-free survival. In a total of 71 974 person-years of follow-up among the offspring, 718 incident CVD events occurred. The overall CVD incidence rate was 10 per 1000 person-years [95% confidence interval (CI) 9.3-10.7]. Offspring of mothers with ideal CVH lived 9 more years free of CVD than offspring of mothers with poor CVH (P < 0.001). Maternal poor CVH was associated with twice as high hazard of early onset of CVD compared with maternal ideal CVH (adjusted Hazard Ratio 2.09, 95% CI 1.50-2.92). No statistically significant association was observed in the hazards of CVD-free survival by paternal CVH categories.

CONCLUSIONS

We found that offspring of parents with ideal CVH had a greater CVD-free survival. Maternal CVH was a more robust predictor of offspring's CVD-free survival than paternal CVH, underscoring the need for clinical and policy interventions that involve mothers to break the intergenerational cycle of CVD-related morbidity and mortality.

Non-invasive prenatal testing reveals copy number variations related to pregnancy complications

Background

Pregnancy complications could lead to maternal and fetal morbidity and mortality. Early diagnosing and managing complications have been associated with good outcomes. The placenta was an important organ for development of pregnancy complications. Thus, non-invasive prenatal testing technologies could detect genetic variations, such as aneuploidies and sub-chromosomal copy number variations, reflecting defective placenta by maternal plasma cffDNAs. Maternal cffDNAs had been proved to derive from trophoblast cells of placenta.

Results

In order to find out the relationship between genetic variations and pregnancy complications, we reviewed NIPT results for subchromosomal copy number variations in a cohort of 3890 pregnancies without complications and 441 pregnancies with pregnancy complications including gestational diabetes mellitus (GDM), pregnancy-induced hypertension (PIH), preterm prelabor rupture of membranes (PPROM) and placenta implantation abnormalities (PIA). For GDMs, we identified three CNV regions containing some members of alpha- and beta-defensins, such as DEFA1, DEFA3, DEFB1. For PIHs, we found three duplication and one deletion region including Pcdhα, Pcdhβ, and Pcdhγ, known as protocadherins, which were complicated by hypertensive disorders. For PPROMs and PIAs, we identified one and two CNV regions, respectively. SFTPA2, SFTPD and SFTPA1, belonging to surfactant protein, was considered to moderated the inflammatory activation within the fetal extra-embryonic compartment, associated to duration of preterm prelabor rupture of fetal membranes, while MEF2C and TM6SF1 could be involved in trophoblast invasion and differentiation.

Conclusions

Our findings gave a clue to correlation between genetic variations of maternal cell-free DNAs and pregnancy complications.

Electronic supplementary material

The online version of this article (10.1186/s13039-019-0451-3) contains supplementary material, which is available to authorized users.

Human placental methylome in the interplay of adverse placental health, environmental exposure, and pregnancy outcome

The placenta is the interface between maternal and fetal circulations, integrating maternal and fetal signals to selectively regulate nutrient, gas, and waste exchange, as well as secrete hormones. In turn, the placenta helps create the in utero environment and control fetal growth and development. The unique epigenetic profile of the human placenta likely reflects its early developmental separation from the fetus proper and its role in mediating maternal–fetal exchange that leaves it open to a range of exogenous exposures in the maternal circulation. In this review, we cover recent advances in DNA methylation in the context of placental function and development, as well as the interaction between the pregnancy and the environment.