Sexual epigenetic dimorphism in the human placenta: implications for susceptibility during the prenatal period

Neonatal inflammation and its association with asthma and obesity in late childhood among individuals born extremely preterm

BACKGROUND

Asthma and obesity are frequent outcomes among individuals born extremely preterm and are associated with decreased lifespan. Neonatal inflammation is associated with chronic neurodevelopmental disorders; however, it is less studied in association with other later childhood chronic disorders in this population.

METHODS

Fourteen hospitals in 5 U.S. states enrolled 1506 infants born before 28 weeks of gestation in the Extremely Low Gestational Age Newborn cohort in 2004-2014. Neonatal blood spots were collected on postnatal days 1, 7, 14, 21, and 28, and used to measure 14 inflammation-related proteins. Associations were evaluated between high (top quartile) levels of proteins and two chronic health disorders at ages 10 and 15 years: physician-diagnosed asthma and obesity (body mass index ≥95th percentile).

RESULTS

Few associations were found between high levels of 14 inflammation-related proteins, either on a single day or on multiple days, and either asthma or obesity. Similarly, few associations were found in analyses stratified by sex or presence/absence of prenatal inflammation.

CONCLUSIONS

In extremely preterm newborns, systemic elevations of inflammation-related proteins during the neonatal period were not associated with childhood asthma and obesity outcomes at 10 or 15 years of age.

IMPACT

In the large multi-center Extremely Low Gestational Age Newborn (ELGAN) cohort, sustained elevation of neonatal levels of inflammation-related proteins was not consistently associated with asthma or obesity outcomes at 10 or 15 years of age. This finding contrasts with reported associations of perinatal inflammation with obesity at 2 years and neurodevelopmental disorders at 2-15 years in the ELGANs, suggesting that unlike neurodevelopment, peripubertal obesity and asthma may be driven by later childhood exposures. Future research on perinatal mechanisms of childhood asthma and obesity should account for both fetal and later exposures and pathways in addition to inflammation at birth.

Epigenetic mechanisms of osteoarthritis risk in human skeletal development

The epigenome, including the methylation of cytosine bases at CG dinucleotides, is intrinsically linked to transcriptional regulation. The tight regulation of gene expression during skeletal development is essential, with ~1/500 individuals born with skeletal abnormalities. Furthermore, increasing evidence is emerging to link age-associated complex genetic musculoskeletal diseases, including osteoarthritis (OA), to developmental factors including joint shape. Multiple studies have shown a functional role for DNA methylation in the genetic mechanisms of OA risk using articular cartilage samples taken from aged patients. Despite this, our knowledge of temporal changes to the methylome during human cartilage development has been limited. We quantified DNA methylation at ~700,000 individual CpGs across the epigenome of developing human articular cartilage in 72 samples ranging from 7-21 post-conception weeks, a time period that includes cavitation of the developing knee joint. We identified significant changes in 8% of all CpGs, and >9400 developmental differentially methylated regions (dDMRs). The largest hypermethylated dDMRs mapped to transcriptional regulators of early skeletal patterning including MEIS1 and IRX1. Conversely, the largest hypomethylated dDMRs mapped to genes encoding extracellular matrix proteins including SPON2 and TNXB and were enriched in chondrocyte enhancers. Significant correlations were identified between the expression of these genes and methylation within the hypomethylated dDMRs. We further identified 811 CpGs at which significant dimorphism was present between the male and female samples, with the majority (68%) being hypermethylated in female samples. Following imputation, we captured the genotype of these samples at >5 million variants and performed epigenome-wide methylation quantitative trait locus (mQTL) analysis. Colocalization analysis identified 26 loci at which genetic variants exhibited shared impacts upon methylation and OA genetic risk. This included loci which have been previously reported to harbour OA-mQTLs (including GDF5 and ALDH1A2), yet the majority (73%) were novel (including those mapping to CHST3, FGF1 and TEAD1). To our knowledge, this is the first extensive study of DNA methylation across human articular cartilage development. We identify considerable methylomic plasticity within the development of knee cartilage and report active epigenomic mediators of OA risk operating in prenatal joint tissues.

Sex-Dependent Differences in Mouse Placental Gene Expression following a Maternal High-Fat Diet

OBJECTIVE

 In utero fetal exposures may have sex-specific placental gene responses. Our objective was to measure sex-based differences in placental gene expression from dams fed high-fat diet (HFD) versus control diet (CD).

STUDY DESIGN

 We fed timed pregnant Friend virus B-strain dams either a CD (n = 5) or an HFD (n = 5). We euthanized dams on embryonic day 17.5 to collect placentas. We extracted placental RNA and hybridized it to a customized 96-gene Nanostring panel focusing on angiogenic, inflammatory, and growth genes. We compared normalized gene expression between CD and HFD, stratified by fetal sex, using analysis of variance. Pathway analysis was used to further interpret the genomic data.

RESULTS

 Pups from HFD-fed dams were heavier than those from CD-fed dams (0.97 ± 0.06 vs. 0.84 ± 0.08 g, p < 0.001). Male pups were heavier than females in the HFD (0.99 ± 0.05 vs. 0.94 ± 0.06 g, p = 0.004) but not CD (0.87 ± 0.08 vs. 0.83 ± 0.07 g, p = 0.10) group. No sex-based differences in placental gene expression in CD-fed dams were observed. Among HFD-fed dams, placentas from female pups exhibited upregulation of 15 genes (q = 0.01). Network analyses identified a cluster of genes involved in carbohydrate metabolism, cellular function and maintenance, and endocrine system development and function (p = 1 × 10-23). The observed female-specific increased gene expression following in utero HFD exposure was predicted to be regulated by insulin (p = 5.79 × 10-13).

CONCLUSION

 In female compared with male pups, in utero exposure to HFD upregulated placental gene expression in 15 genes predicted to be regulated by insulin. Sex-specific differences in placental expression of these genes should be further investigated.

KEY POINTS

· Male pups were heavier than female pups at the time of sacrifice when dams were fed an HFD.. · HFD was associated with upregulated gene expression in female placentas.. · Female-specific increased gene was predicted to be regulated by insulin..

Sex differences in DNA methylation across gestation: a large scale, cross-cohort, multi-tissue analysis

Biological sex is a key variable influencing many physiological systems. Disease prevalence as well as treatment success can be modified by sex. Differences emerge already early in life and include pregnancy complications and adverse birth outcomes. The placenta is a critical organ for fetal development and shows sex-based differences in the expression of hormones and cytokines. Epigenetic regulation, such as DNA methylation (DNAm), may underlie the previously reported placental sexual dimorphism. We associated placental DNAm with fetal sex in three cohorts. Individual cohort results were meta-analyzed with random-effects modelling. CpG-sites differentially methylated with sex were further investigated regarding pathway enrichment, overlap with methylation quantitative trait loci (meQTLs), and hits from phenome-wide association studies (PheWAS). We evaluated the consistency of findings across tissues (CVS, i.e. chorionic villus sampling from early placenta, and cord blood) as well as with gene expression. We identified 10,320 epigenome-wide significant sex-differentially methylated probes (DMPs) spread throughout the epigenome of the placenta at birth. Most DMPs presented with lower DNAm levels in females. DMPs mapped to genes upregulated in brain, were enriched for neurodevelopmental pathways and significantly overlapped with meQTLs and PheWAS hits. Effect sizes were moderately correlated between CVS and placenta at birth, but only weakly correlated between birth placenta and cord blood. Sex differential gene expression in birth placenta was less pronounced and implicated genetic regions only marginally overlapped with those associated with differential DNAm. Our study provides an integrative perspective on sex-differential DNAm in perinatal tissues underscoring the possible link between placenta and brain.

Epigenetic associations in HPA axis genes related to bronchopulmonary dysplasia and antenatal steroids

BACKGROUND

Bronchopulmonary dysplasia (BPD), a common morbidity among very preterm infants, is associated with chronic disease and neurodevelopmental impairments. A hypothesized mechanism for these outcomes lies in altered glucocorticoid (GC) activity. We hypothesized that BPD and its treatments may result in epigenetic differences in the hypothalamic-pituitary-adrenal (HPA) axis, which is modulated by GC, and could be ascertained using an established GC risk score and DNA methylation (DNAm) of HPA axis genes.

METHODS

DNAm was quantified from buccal tissue (ECHO-NOVI) and from neonatal blood spots (ELGAN ECHO) via the EPIC microarray. Prenatal maternal characteristics, pregnancy complication, and neonatal medical complication data were collected from medical record review and maternal interviews.

RESULTS

The GC score was not associated with steroid exposure or BPD. However, six HPA genes involved in stress response regulation demonstrated differential methylation with antenatal steroid exposure; two CpGs within FKBP5 and POMC were differentially methylated with BPD severity. These findings were sex-specific in both cohorts; males had greater magnitude of differential methylation within these genes.

CONCLUSIONS

These findings suggest that BPD severity and antenatal steroids are associated with DNAm at some HPA genes in very preterm infants and the effects appear to be sex-, tissue-, and age-specific.

IMPACT

This study addresses bronchopulmonary dysplasia (BPD), an important health outcome among preterm neonates, and interrogates a commonly studied pathway, the hypothalamic-pituitary-adrenal (HPA) axis. The combination of BPD, the HPA axis, and epigenetic markers has not been previously reported. In this study, we found that BPD itself was not associated with epigenetic responses in the HPA axis in infants born very preterm; however, antenatal treatment with steroids was associated with epigenetic responses.

Sex-dependent placental methylation quantitative trait loci provide insight into the prenatal origins of childhood onset traits and conditions

Molecular quantitative trait loci (QTLs) allow us to understand the biology captured in genome-wide association studies (GWASs). The placenta regulates fetal development and shows sex differences in DNA methylation. We therefore hypothesized that placental methylation QTL (mQTL) explain variation in genetic risk for childhood onset traits, and that effects differ by sex. We analyzed 411 term placentas from two studies and found 49,252 methylation (CpG) sites with mQTL and 2,489 CpG sites with sex-dependent mQTL. All mQTL were enriched in regions that typically affect gene expression in prenatal tissues. All mQTL were also enriched in GWAS results for growth- and immune-related traits, but male- and female-specific mQTL were more enriched than cross-sex mQTL. mQTL colocalized with trait loci at 777 CpG sites, with 216 (28%) specific to males or females. Overall, mQTL specific to male and female placenta capture otherwise overlooked variation in childhood traits.

Molecular pathways in placental-fetal development and disruption

The first trimester of pregnancy ranks high in priority when minimizing harmful exposures, given the wide-ranging types of organogenesis occurring between 4- and 12-weeks' gestation. One way to quantify potential harm to the fetus in the first trimester is to measure a corollary effect on the placenta. Placental biomarkers are widely present in maternal circulation, cord blood, and placental tissue biopsied at birth or at the time of pregnancy termination. Here we evaluate ten diverse pathways involving molecules expressed in the first trimester human placenta based on their relevance to normal fetal development and to the hypothesis of placental-fetal endocrine disruption (perturbation in development that results in abnormal endocrine function in the offspring), namely: human chorionic gonadotropin (hCG), thyroid hormone regulation, peroxisome proliferator activated receptor protein gamma (PPARγ), leptin, transforming growth factor beta, epiregulin, growth differentiation factor 15, small nucleolar RNAs, serotonin, and vitamin D. Some of these are well-established as biomarkers of placental-fetal endocrine disruption, while others are not well studied and were selected based on discovery analyses of the placental transcriptome. A literature search on these biomarkers summarizes evidence of placenta-specific production and regulation of each biomarker, and their role in fetal reproductive tract, brain, and other specific domains of fetal development. In this review, we extend the theory of fetal programming to placental-fetal programming.

Sex-based disparities in DNA methylation and gene expression in late-gestation mouse placentas

BACKGROUND

The placenta is vital for fetal development and its contributions to various developmental issues, such as pregnancy complications, fetal growth restriction, and maternal exposure, have been extensively studied in mice. The placenta forms mainly from fetal tissue and therefore has the same biological sex as the fetus it supports. Extensive research has delved into the placenta's involvement in pregnancy complications and future offspring development, with a notable emphasis on exploring sex-specific disparities. However, despite these investigations, sex-based disparities in epigenetic (e.g., DNA methylation) and transcriptomic features of the late-gestation mouse placenta remain largely unknown.

METHODS

We collected male and female mouse placentas at late gestation (E18.5, n = 3/sex) and performed next-generation sequencing to identify genome-wide sex differences in transcription and DNA methylation.

RESULTS

Our comparison between male and female revealed 358 differentially expressed genes (DEGs) on autosomes, which were associated with signaling pathways involved in transmembrane transport and the responses to viruses and external stimuli. X chromosome DEGs (n = 39) were associated with different pathways, including those regulating chromatin modification and small GTPase-mediated signal transduction. Differentially methylated regions (DMRs) were more common on the X chromosomes (n = 3756) than on autosomes (n = 1705). Interestingly, while most X chromosome DMRs had higher DNA methylation levels in female placentas and tended to be included in CpG dinucleotide-rich regions, 73% of autosomal DMRs had higher methylation levels in male placentas and were distant from CpG-rich regions. Several DEGs were correlated with DMRs. A subset of the DMRs present in late-stage placentas were already established in mid-gestation (E10.5) placentas (n = 348 DMRs on X chromosome and 19 DMRs on autosomes), while others were acquired later in placental development.

CONCLUSION

Our study provides comprehensive lists of DEGs and DMRs between male and female that collectively cause profound differences in the DNA methylation and gene expression profiles of late-gestation mouse placentas. Our results demonstrate the importance of incorporating sex-specific analyses into epigenetic and transcription studies to enhance the accuracy and comprehensiveness of their conclusions and help address the significant knowledge gap regarding how sex differences influence placental function.

Sex-specific DNA methylation in saliva from the multi-ethnic Future of Families and Child Wellbeing Study

The prevalence and severity of many diseases differs by sex, potentially due to sex-specific patterns in DNA methylation. Autosomal sex-specific differences in DNA methylation have been observed in cord blood and placental tissue but are not well studied in saliva or in diverse populations. We sought to characterize sex-specific DNA methylation on autosomal chromosomes in saliva samples from children in the Future of Families and Child Wellbeing Study, a multi-ethnic prospective birth cohort containing an oversampling of Black, Hispanic and low-income families. DNA methylation from saliva samples was analysed on 796 children (50.6% male) at both ages 9 and 15 with DNA methylation measured using the Illumina HumanMethylation 450k array. An epigenome-wide association analysis of the age 9 samples identified 8,430 sex-differentiated autosomal DNA methylation sites (P < 2.4 × 10-7), of which 76.2% had higher DNA methylation in female children. The strongest sex-difference was in the cg26921482 probe, in the AMDHD2 gene, with 30.6% higher DNA methylation in female compared to male children (P < 1 × 10-300). Treating the age 15 samples as an internal replication set, we observed highly consistent results between the ages 9 and 15 measurements, indicating stable and replicable sex-differentiation. Further, we directly compared our results to previously published DNA methylation sex differences in both cord blood and saliva and again found strong consistency. Our findings support widespread and robust sex-differential DNA methylation across age, human tissues, and populations. These findings help inform our understanding of potential biological processes contributing to sex differences in human physiology and disease.

Sex-based differences in placental DNA methylation profiles related to gestational age: an NIH ECHO meta-analysis

The placenta undergoes many changes throughout gestation to support the evolving needs of the foetus. There is also a growing appreciation that male and female foetuses develop differently in utero, with unique epigenetic changes in placental tissue. Here, we report meta-analysed sex-specific associations between gestational age and placental DNA methylation from four cohorts in the National Institutes of Health (NIH) Environmental influences on Child Health Outcomes (ECHO) Programme (355 females/419 males, gestational ages 23-42 weeks). We identified 407 cytosine-guanine dinucleotides (CpGs) in females and 794 in males where placental methylation levels were associated with gestational age. After cell-type adjustment, 55 CpGs in females and 826 in males were significant. These were enriched for biological processes critical to the immune system in females and transmembrane transport in males. Our findings are distinct between the sexes: in females, associations with gestational age are largely explained by differences in placental cellular composition, whereas in males, gestational age is directly associated with numerous alterations in methylation levels.

Prenatal Metal Exposure Alters the Placental Proteome in a Sex-Dependent Manner in Extremely Low Gestational Age Newborns: Links to Gestational Age

Prenatal exposure to toxic metals is associated with altered placental function and adverse infant and child health outcomes. Adverse outcomes include those that are observed at the time of birth, such as low birthweight, as well as those that arise later in life, such as neurological impairment. It is often the case that these adverse outcomes show sex-specific responses in relation to toxicant exposures. While the precise molecular mechanisms linking in utero toxic metal exposures with later-in-life health are unknown, placental inflammation is posited to play a critical role. Here, we sought to understand whether in utero metal exposure is associated with alterations in the expression of the placental proteome by identifying metal associated proteins (MAPs). Within the Extremely Low Gestational Age Newborns (ELGAN) cohort (n = 230), placental and umbilical cord tissue samples were collected at birth. Arsenic (As), cadmium (Cd), lead (Pb), selenium (Se), and manganese (Mn) concentrations were measured in umbilical cord tissue samples via ICP-MS/MS. Protein expression was examined in placental samples using an LC-MS/MS-based, global, untargeted proteomics analysis measuring more than 3400 proteins. MAPs were then evaluated for associations with pregnancy and neonatal outcomes, including placental weight and gestational age. We hypothesized that metal levels would be positively associated with the altered expression of inflammation/immune-associated pathways and that sex-specific patterns of metal-associated placental protein expression would be observed. Sex-specific analyses identified 89 unique MAPs expressed in female placentas and 41 unique MAPs expressed in male placentas. Notably, many of the female-associated MAPs are known to be involved in immune-related processes, while the male-associated MAPs are associated with intracellular transport and cell localization. Further, several MAPs were significantly associated with gestational age in males and females and placental weight in males. These data highlight the linkage between prenatal metal exposure and an altered placental proteome, with implications for altering the trajectory of fetal development.

The application of epiphenotyping approaches to DNA methylation array studies of the human placenta

BACKGROUND

Genome-wide DNA methylation (DNAme) profiling of the placenta with Illumina Infinium Methylation bead arrays is often used to explore the connections between in utero exposures, placental pathology, and fetal development. However, many technical and biological factors can lead to signals of DNAme variation between samples and between cohorts, and understanding and accounting for these factors is essential to ensure meaningful and replicable data analysis. Recently, "epiphenotyping" approaches have been developed whereby DNAme data can be used to impute information about phenotypic variables such as gestational age, sex, cell composition, and ancestry. These epiphenotypes offer avenues to compare phenotypic data across cohorts, and to understand how phenotypic variables relate to DNAme variability. However, the relationships between placental epiphenotyping variables and other technical and biological variables, and their application to downstream epigenome analyses, have not been well studied.

RESULTS

Using DNAme data from 204 placentas across three cohorts, we applied the PlaNET R package to estimate epiphenotypes gestational age, ancestry, and cell composition in these samples. PlaNET ancestry estimates were highly correlated with independent polymorphic ancestry-informative markers, and epigenetic gestational age, on average, was estimated within 4 days of reported gestational age, underscoring the accuracy of these tools. Cell composition estimates varied both within and between cohorts, as well as over very long placental processing times. Interestingly, the ratio of cytotrophoblast to syncytiotrophoblast proportion decreased with increasing gestational age, and differed slightly by both maternal ethnicity (lower in white vs. non-white) and genetic ancestry (lower in higher probability European ancestry). The cohort of origin and cytotrophoblast proportion were the largest drivers of DNAme variation in this dataset, based on their associations with the first principal component.

CONCLUSIONS

This work confirms that cohort, array (technical) batch, cell type proportion, self-reported ethnicity, genetic ancestry, and biological sex are important variables to consider in any analyses of Illumina DNAme data. We further demonstrate the specific utility of epiphenotyping tools developed for use with placental DNAme data, and show that these variables (i) provide an independent check of clinically obtained data and (ii) provide a robust approach to compare variables across different datasets. Finally, we present a general framework for the processing and analysis of placental DNAme data, integrating the epiphenotype variables discussed here.

Regulation of sexually dimorphic placental adaptation in LPS exposure-induced intrauterine growth restriction

BACKGROUND

Sexual dimorphism in placental physiology affects the functionality of placental adaptation during adverse pregnancy. Defects of placental function compromise fetal programming, affecting the offspring's adult life. However, studies focusing on the relationship between sex-specific placental adaptation and consequent fetal maldevelopment under sub-optimal uterus milieu are still elusive.

METHODS

Here, we investigated the effects of maternal lipopolysaccharide (LPS) exposure between placental sex. Pregnant ICR mice received intraperitoneal injection of phosphate-buffered saline or 100, 200, and 400 µg/kg LPS on the gestational day (GD) 15.5. To determine whether prenatal maternal LPS exposure resulted in complicated pregnancy outcomes, survival rate of embryos was calculated and the growth of embryos and placentas was examined. To elucidate global transcriptomic changes occurring in the placenta, total RNA-sequencing (RNA-seq) was performed in female and male placentas.

RESULTS

LPS administration induced placental inflammation in both sexes at GD 17.5. Prenatal infection resulted in growth retardation in both sexes of embryos, and especially more prevalently in male. Impaired placental development was observed in a sex-specific manner. LPS 400 µg/kg reduced the percentage area of the labyrinth in females and junctional zone in males, respectively. RNA-sequencing revealed widespread sexually dimorphic transcriptional changes in placenta. In particular, representative changes were involved in biological processes such as trophoblast differentiation, nutrient/ion transporter, pregnancy, and immune system.

CONCLUSIONS

Our results present the sexually dimorphic responses of placental physiology in intrauterine growth restriction model and provide tentative relationship further to be elucidated between sex-biased placental functional change and long-term effects on the offspring's later life.

Sex differences in innate and adaptive immunity impact fetal, placental, and maternal health†

The differences between males and females begin shortly after birth, continue throughout prenatal development, and eventually extend into childhood and adult life. Male embryos and fetuses prioritize proliferation and growth, often at the expense of the fetoplacental energy reserves. This singular focus on growth over adaptability leaves male fetuses and neonates vulnerable to adverse outcomes during pregnancy and birth and can have lasting impacts throughout life. Beyond this prioritization of growth, male placentas and fetuses also respond to infection and inflammation differently than female counterparts. Pregnancies carrying female fetuses have a more regulatory immune response, whereas pregnancies carrying male fetuses have a stronger inflammatory response. These differences can be seen as early as the innate immune response with differences in cytokine and chemokine signaling. The sexual dimorphism in immunity then continues into the adaptive immune response with differences in T-cell biology and antibody production and transfer. As it appears that these sex-specific differences are amplified in pathologic pregnancies, it stands to reason that differences in the placental, fetal, and maternal immune responses in pregnancy contribute to increased male perinatal morbidity and mortality. In this review, we will describe the genetic and hormonal contributions to the sexual dimorphism of fetal and placental immunity. We will also discuss current research efforts to describe the sex-specific differences of the maternal-fetal interface and how it impacts fetal and maternal health.

Sexually dimorphic methylation patterns characterize the placenta and blood from extremely preterm newborns

BACKGROUND

Health outcomes among children born prematurely are known to be sexually dimorphic, with male infants often more affected, yet the mechanism behind this observation is not clear. CpG methylation levels in the placenta and blood also differ by sex and are associated with adverse health outcomes. We contrasted CpG methylation levels in the placenta and neonatal blood (n = 358) from the Extremely Low Gestational Age Newborn (ELGAN) cohort based on the EPIC array, which assays over 850,000 CpG sites across the epigenome. Sex-specific epigenome-wide association analyses were conducted for the placenta and neonatal blood samples independently, and the results were compared to determine tissue-specific differences between the methylation patterns in males and females. All models were adjusted for cell type heterogeneity. Enrichment pathway analysis was performed to identify the biological functions of genes related to the sexually dimorphic CpG sites.

RESULTS

Approximately 11,500 CpG sites were differentially methylated in relation to sex. Of these, 5949 were placenta-specific and 5361 were blood-specific, with only 233 CpG sites overlapping in both tissues. For placenta-specific CpG sites, 90% were hypermethylated in males. For blood-specific CpG sites, 95% were hypermethylated in females. In the placenta, keratinocyte differentiation biological pathways were enriched among the differentially methylated genes. No enrichment pathways were observed for blood.

CONCLUSIONS

Distinct methylation patterns were observed between male and female children born extremely premature, and keratinocyte differentiation pathways were enriched in the placenta. These findings provide new insights into the epigenetic mechanisms underlying sexually dimorphic health outcomes among extremely premature infants.

Epigenome-Wide Associations of Placental DNA Methylation and Behavioral and Emotional Difficulties in Children at 3 Years of Age

The placenta is a key organ for fetal and brain development. Its epigenome can be regarded as a biochemical record of the prenatal environment and a potential mechanism of its association with the future health of the fetus. We investigated associations between placental DNA methylation levels and child behavioral and emotional difficulties, assessed at 3 years of age using the Strengths and Difficulties Questionnaire (SDQ) in 441 mother-child dyads from the EDEN cohort. Hypothesis-driven and exploratory analyses (on differentially methylated probes (EWAS) and regions (DMR)) were adjusted for confounders, technical factors, and cell composition estimates, corrected for multiple comparisons, and stratified by child sex. Hypothesis-driven analyses showed an association of cg26703534 (AHRR) with emotional symptoms, and exploratory analyses identified two probes, cg09126090 (intergenic region) and cg10305789 (PPP1R16B), as negatively associated with peer relationship problems, as well as 33 DMRs, mostly positively associated with at least one of the SDQ subscales. Among girls, most associations were seen with emotional difficulties, whereas in boys, DMRs were as much associated with emotional than behavioral difficulties. This study provides the first evidence of associations between placental DNA methylation and child behavioral and emotional difficulties. Our results suggest sex-specific associations and might provide new insights into the mechanisms of neurodevelopment.

Prenatal exposure to legacy PFAS and neurodevelopment in preschool-aged Canadian children: The MIREC cohort

BACKGROUND

Exposure to perfluoroalkyl substances (PFAS) has been shown to be neurotoxic in experimental studies, but epidemiological evidence linking prenatal PFAS exposure to child neurodevelopment is equivocal and scarce.

OBJECTIVE

To quantify associations between prenatal exposure to legacy PFAS and children's intelligence (IQ) and executive functioning (EF) in a Canadian pregnancy and birth cohort and to determine if these associations differ by child sex.

METHODS

We measured first-trimester plasma concentrations of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexanesulfonic acid (PFHxS) in the Maternal-Infant Research on Environmental Chemicals (MIREC) study and assessed children's full-scale (n = 522), performance (n = 517), and verbal (n = 519) IQ using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III). Children's working memory (n = 513) and ability to plan and organize (n = 514) were assessed using a parent-reported questionnaire, the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P). We quantified associations between individual log2-transformed PFAS exposure and children's IQ and EF using multiple linear regression analyses and evaluated effect modification by child sex. We also used Repeated Holdout Weighted Quantile Sum (WQS) regression models with effect modification by child sex to quantify the effect of combined exposure to all three PFAS chemicals on IQ and EF. All models were adjusted for key sociodemographic characteristics.

RESULTS

Geometric mean plasma concentrations (IQR) for PFOA, PFOS and PFHxS were 1.68 (1.10-2.50), 4.97 (3.20-6.20) and 1.09 (0.67-1.60) μg/L respectively. We found evidence of effect modification by child sex in all models examining performance IQ (p < .01). Specifically, every doubling of PFOA, PFOS, and or PFHxS was inversely associated with performance IQ, but only in males (PFOA: B = -2.80, 95% CI: -4.92, -0.68; PFOS: B = -2.64, 95% CI: -4.77, -0.52; PFHxS: B = -2.92, 95% CI: -4.72, -1.12). Similarly, every quartile increase in the WQS index was associated with poorer performance IQ in males (B = -3.16, 95% CI: -4.90, -1.43), with PFHxS contributing the largest weight to the index. In contrast, no significant association was found for females (B = 0.63, 95% CI: -0.99, 2.26). No significant associations were found for EF in either males or females.

CONCLUSIONS

Higher prenatal PFAS exposure was associated with lower performance IQ in males, suggesting that this association may be sex- and domain-specific.

The application of epiphenotyping approaches to DNA methylation array studies of the human placenta

Background : Genome-wide DNA methylation (DNAme) profiling of the placenta with Illumina Infinium Methylation bead arrays is often used to explore the connections between in utero exposures, placental pathology, and fetal development. However, many technical and biological factors can lead to signals of DNAme variation between samples and between cohorts, and understanding and accounting for these factors is essential to ensure meaningful and replicable data analysis. Recently, "epiphenotyping" approaches have been developed whereby DNAme data can be used to impute information about phenotypic variables such as gestational age, sex, cell composition, and ancestry. These epiphenotypes offer avenues to compare phenotypic data across cohorts, and to understand how phenotypic variables relate to DNAme variability. However, the relationships between placental epiphenotyping variables and other technical and biological variables, and their application to downstream epigenome analyses, have not been well studied. Results : Using DNAme data from 204 placentas across three cohorts, we applied the PlaNET R package to estimate epiphenotypes gestational age, ancestry, and cell composition in these samples. PlaNET ancestry estimates were highly correlated with independent polymorphic ancestry informative markers, and epigenetic gestational age, on average, was estimated within 4 days of reported gestational age, underscoring the accuracy of these tools. Cell composition estimates varied both within and between cohorts, but reassuringly were robust to placental processing time. Interestingly, the ratio of cytotrophoblast to syncytiotrophoblast proportion decreased with increasing gestational age, and differed slightly by both maternal ethnicity (lower in white vs. non-white) and genetic ancestry (lower in higher probability European ancestry). The cohort of origin and cytotrophoblast proportion were the largest drivers of DNAme variation in this dataset, based on their associations with the first principal component. Conclusions : This work confirms that cohort, array (technical) batch, cell type proportion, self-reported ethnicity, genetic ancestry, and biological sex are important variables to consider in any analyses of Illumina DNAme data. Further, we demonstrate that estimating epiphenotype variables from the DNAme data itself, when possible, provides both an independent check of clinically-obtained data and can provide a robust approach to compare variables across different datasets.

Environmental influences on child health outcomes: cohorts of individuals born very preterm

The National Institutes of Health's Environmental influences on Child Health Outcomes (ECHO) Program was designed to address solution-oriented research questions about the links between children's early life environment and their risks of pre-, peri-, and post-natal complications, asthma, obesity, neurodevelopmental disorders, and positive health. Children born very preterm are at increased risk for many of the outcomes on which ECHO focuses, but the contributions of environmental factors to this risk are not well characterized. Three ECHO cohorts consist almost exclusively of individuals born very preterm. Data provided to ECHO from cohorts can be used to address hypotheses about (1) differential risks of chronic health and developmental conditions between individuals born very preterm and those born at term; (2) health disparities across social determinants of health; and (3) mechanisms linking early-life exposures and later-life outcomes among individuals born very preterm. IMPACT: The National Institutes of Health's Environmental Influences on Child Health Outcomes Program is conducting solution-oriented research on the links between children's environment and health. Three ECHO cohorts comprise study participants born very preterm; these cohorts have enrolled, to date, 1751 individuals born in 14 states in the U.S. in between April 2002 and March 2020. Extensive data are available on early-life environmental exposures and child outcomes related to neurodevelopment, asthma, obesity, and positive health. Data from ECHO preterm cohorts can be used to address questions about the combined effects of preterm birth and environmental exposures on child health outcomes.

Massive Neonatal Arterial Ischemic Stroke

BACKGROUND

Massive infarction in adults is a devastating entity characterized by signs of extreme swelling of the brain's parenchyma. We explored whether a similar entity exists in neonates, which we call massive neonatal arterial ischemic stroke (M-NAIS), and assess its potential clinical implications.

METHODS

Prospective multicenter cohort study comprising 48 neonates with gestational age ≥35 weeks with middle cerebral artery (MCA) NAIS was performed. Diagnosis with magnetic resonance imaging (MRI) was performed within the first three days after symptom onset. The presence of signs of a space-occupying mass, such as brain midline shift and/or ventricular and/or extra-axial space collapse, was recorded. The volume of the infarct and brain midline shift were determined with semiautomatic procedures. Neurodevelopment was assessed at age 24 months.

RESULTS

Fifteen (31%) neonates presented MRI signs of a space-occupying mass effect and were considered to have an M-NAIS. The relative volume (infarct volume/total brain volume) of the infarct was on average significantly greater in the M-NAIS subgroup (29% vs 4.9%, P < 0.001). Patients with M-NAIS consistently presented lesions involving the M1 arterial territory of the MCA and showed more apneic and tonic seizures, which had an earlier onset and lasted longer. Moderate to severe adverse neurodevelopmental outcomes were present in most M-NAIS cases (79% vs 6%, P < 0.001).

CONCLUSIONS

M-NAIS appears to be a distinctive subtype of neonatal infarction, defined by characteristic neuroimaging signs. Neonates with M-NAIS frequently present a moderate to severe adverse outcome. Early M-NAIS identification would allow for prompt, specific rehabilitation interventions and would provide more accurate prognostic information to families.

CpG methylation patterns in placenta and neonatal blood are differentially associated with neonatal inflammation

BACKGROUND

Infants born extremely premature are at increased risk for health complications later in life for which neonatal inflammation may be a contributing biological driver. Placental CpG methylation provides mechanistic information regarding the relationship between prenatal epigenetic programming, prematurity, neonatal inflammation, and later-in-life health.

METHODS

We contrasted CpG methylation in the placenta and neonatal blood spots in relation to neonatal inflammation in the Extremely Low Gestational Age Newborn (ELGAN) cohort. Neonatal inflammation status was based on the expression of six inflammation-related proteins, assessed as (1) day-one inflammation (DOI) or (2) intermittent or sustained systemic inflammation (ISSI, inflammation on ≥2 days in the first 2 postnatal weeks). Epigenome-wide CpG methylation was assessed in 354 placental samples and 318 neonatal blood samples.

RESULTS

Placental CpG methylation displayed the strongest association with ISSI (48 CpG sites) but was not associated with DOI. This was in contrast to CpG methylation in blood spots, which was associated with DOI (111 CpG sites) and not with ISSI (one CpG site).

CONCLUSIONS

Placental CpG methylation was strongly associated with ISSI, a measure of inflammation previously linked to later-in-life cognitive impairment, while day-one neonatal blood methylation was associated with DOI.

IMPACT

Neonatal inflammation increases the risk of adverse later-life outcomes, especially in infants born extremely preterm. CpG methylation in the placenta and neonatal blood spots were evaluated in relation to neonatal inflammation assessed via circulating proteins as either (i) day-one inflammation (DOI) or (ii) intermittent or sustained systemic inflammation (ISSI, inflammation on ≥2 days in the first 2 weeks). Tissue specificity was observed in epigenetic-inflammatory relationships: placental CpG methylation was associated with ISSI, neonatal blood CpG methylation was associated with DOI. Supporting the placental origins of disease framework, placental epigenetic patterns are associated with a propensity for ISSI in neonates.

Beadchip technology to detect DNA methylation in mouse faithfully recapitulates whole-genome bisulfite sequencing

Aim: To facilitate wide-scale implementation of Illumina Mouse Methylation BeadChip (MMB) technology, array-based measurement of cytosine methylation was compared with the gold-standard assessment of DNA methylation by whole-genome bisulfite sequencing (WGBS). Methods: DNA methylation across two mouse strains (C57B6 and C3H) and both sexes was assessed using the MMB and compared with previously existing deep-coverage WGBS of mice of the same strain and sex. Results & conclusion: The findings demonstrated that 93.3-99.2% of sites had similar measurements of methylation across technologies and that differentially methylated cytosines and regions identified by each technology overlap and enrich for similar biological functions, suggesting that the MMB faithfully recapitulates the findings of WGBS.

Changes in serum omega fatty acids on a Mediterranean diet intervention in patients with gingivitis: An exploratory study

BACKGROUND

Omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) are precursors of pro- and anti-inflammatory lipid mediators. Serum PUFA levels could influence the severity of inflammatory oral diseases, such as gingivitis.

OBJECTIVE

The study analyzed serum PUFA levels in a six-week randomized controlled trial in individuals on the Mediterranean diet (MedD), associations with the intake of specific foods, and possible correlations with oral inflammatory parameters.

METHODS

Data from 37 study participants on either a MedD (MedDG; n = 18) or a "Western diet" in the control group (CG, n = 19) were analyzed. Dental examinations and serum analyses were performed at two time points, T1 (baseline) and T2 (week 6). Serum PUFA status, adherence to the MedD, and data from a Food Frequency Questionnaire were analyzed.

RESULTS

Within the MedDG omega-6 fatty acid levels decreased significantly. In the overall sample, the proportional decrease in sites with bleeding on probing correlated weakly to moderately with the decrease in total omega-6 fatty acid level (Spearman's ρ = 0.274) and the decrease in gingival index correlated moderately with the decrease in linoleic acid level (Spearman's ρ = 0.351). Meat and fast-food consumption correlated positively with levels of various omega-6 fatty acids, whereas nut, fish, and dairy product consumption correlated positively with omega-3 levels.

CONCLUSION

Adherence to a MedD was associated with a decrease in serum omega-6 levels, which positively affected the omega-6/omega-3 ratio. The MedD associated reduction in serum omega-6 levels may be a mechanism that favorably affects gingival inflammatory parameters.

Chromosomal and environmental contributions to sex differences in the vulnerability to neurological and neuropsychiatric disorders: Implications for therapeutic interventions

Neurological and neuropsychiatric disorders affect men and women differently. Multiple sclerosis, Alzheimer's disease, anxiety disorders, depression, meningiomas and late-onset schizophrenia affect women more frequently than men. By contrast, Parkinson's disease, autism spectrum condition, attention-deficit hyperactivity disorder, Tourette's syndrome, amyotrophic lateral sclerosis and early-onset schizophrenia are more prevalent in men. Women have been historically under-recruited or excluded from clinical trials, and most basic research uses male rodent cells or animals as disease models, rarely studying both sexes and factoring sex as a potential source of variation, resulting in a poor understanding of the underlying biological reasons for sex and gender differences in the development of such diseases. Putative pathophysiological contributors include hormones and epigenetics regulators but additional biological and non-biological influences may be at play. We review here the evidence for the underpinning role of the sex chromosome complement, X chromosome inactivation, and environmental and epigenetic regulators in sex differences in the vulnerability to brain disease. We conclude that there is a pressing need for a better understanding of the genetic, epigenetic and environmental mechanisms sustaining sex differences in such diseases, which is critical for developing a precision medicine approach based on sex-tailored prevention and treatment.

The placenta epigenome-brain axis: placental epigenomic and transcriptomic responses that preprogram cognitive impairment

Aim: The placenta-brain axis reflects a developmental linkage where disrupted placental function is associated with impaired neurodevelopment later in life. Placental gene expression and the expression of epigenetic modifiers such as miRNAs may be tied to these impairments and are understudied. Materials & methods: The expression levels of mRNAs (n = 37,268) and their targeting miRNAs (n = 2083) were assessed within placentas collected from the ELGAN study cohort (n = 386). The ELGAN adolescents were assessed for neurocognitive function at age 10 and the association with placental mRNA/miRNAs was determined. Results: Placental mRNAs related to inflammatory and apoptotic processes are under miRNA control and associated with cognitive impairment at age 10. Conclusion: Findings highlight key placenta epigenome-brain relationships that support the developmental origins of health and disease hypothesis.

Fetal sex and risk of preeclampsia: Dose maternal race matter?

OBJECTIVE

To examine whether maternal race could affect the relationship between fetal sex and preeclampsia.

MATERIAL AND METHODS

This study was a cohort analysis using prospectively collected data from pregnant women who participated in the Vitamin Antenatal Asthma Reduction Trial (VDAART). Preeclampsia was the secondary outcome of VDAART. We examined the association of fetal sex with preeclampsia and its potential interaction with maternal race in 813 pregnant women (8% with preeclampsia) in logistic regression models with adjustment for preterm birth (<37 weeks of gestation), maternal age, education, and body mass index at enrollment and clinical center. We further conducted a race stratified analysis and also examined whether any observed association was dependent on the gestational age at delivery and prematurity.

RESULTS

In an analysis of all races combined, preeclampsia was not more common among pregnant women with a male fetus compared to those with a female fetus (odds ratio [OR] = 1.3, 95% CI = 0.81, 2.24). There was an interaction between African American race and fetal sex in association with preeclampsia after adjustment for preterm delivery and other potential confounders (p = .014). In race stratified analyses, we observed higher odds of preeclampsia among African American pregnant women who carried male fetuses after adjustment for preterm delivery and other potential confounders (adjusted OR = 2.4, 95% CI = 1.12, 5.60).

CONCLUSION

We observed fetal sexual dimorphic differences in the occurrence of preeclampsia in African American women, but not in Whites. Information on fetal sex may ultimately improve the prediction of pre-eclampsia in African American mothers, who might be at higher risk for this adverse condition in pregnancy.

Association of fetal sex with angiogenic factors in normotensive and hypertensive pregnancy states

OBJECTIVES

With the incorporation of angiogenic biomarkers into clinical practice, identification of potential modifiers of the angiogenic profile, including fetal sex, is essential.

STUDY DESIGN

In this retrospective cohort analysis, patients with hypertensive disorders of pregnancy (HDP) and normotensive pregnancies were enrolled upon admission to Labor and Delivery. Blood samples for angiogenic factors were assessed using an automated platform. Clinical and demographic information was abstracted from each patient's medical records.

MAIN OUTCOME MEASURES

Soluble fms-like tyrosine kinase-1 (sFlt1) and placental growth factor (PlGF) levels and their ratio in relation to fetal sex in patients with normotensive pregnancies compared to those with HDP were evaluated.

RESULTS

A total of 617 patients were analyzed (299 normotensive, 113 gestational hypertensive, 71 chronic hypertensive, and 134 preeclamptic patients). There was no difference between the number of patients who had a male fetus among preeclampsia and normotensive parturients (56.0 % vs 50.2 %, p = 0.26). Normotensive patients carrying a male fetus had significantly higher sFlt1 (pg/ml) (3168 [IQR: 2160-4945] vs 2678 [IQR: 1752-4271]; p = 0.01) and sFlt1/PlGF ratios (18 [IQR: 7-44] vs 12 [IQR: 5-30]; p = 0.01) in comparison to pregnant patients carrying a female fetus. This difference between fetal sexes was not observed in the angiogenic profile of patients with HDP.

CONCLUSIONS

Our study of primarily Black, obese patients demonstrates that normotensive patients carrying a male fetus have a significantly higher sFlt1 and sFlt1/PlGF ratio as compared to those carrying a female fetus at term gestation. Fetal sex should be considered as a covariate when studying angiogenic factors in normotensive pregnant patients.

Large-scale placenta DNA methylation integrated analysis reveals fetal sex-specific differentially methylated CpG sites and regions

Although male–female differences in placental structure and function have been observed, little is understood about their molecular underpinnings. Here, we present a mega-analysis of 14 publicly available placenta DNA methylation (DNAm) microarray datasets to identify individual CpGs and regions associated with fetal sex. In the discovery dataset of placentas from full term pregnancies (N = 532 samples), 5212 CpGs met genome-wide significance (p < 1E−8) and were enriched in pathways such as keratinization (FDR p-value = 7.37E−14), chemokine activity (FDR p-value = 1.56E−2), and eosinophil migration (FDR p-value = 1.83E−2). Nine differentially methylated regions were identified (fwerArea < 0.1) including a region in the promoter of ZNF300 that showed consistent differential DNAm in samples from earlier timepoints in pregnancy and appeared to be driven predominately by effects in the trophoblast cell type. We describe the largest study of fetal sex differences in placenta DNAm performed to date, revealing genes and pathways characterizing sex-specific placenta function and health outcomes later in life.

Characterising sex differences of autosomal DNA methylation in whole blood using the Illumina EPIC array

BACKGROUND

Sex differences are known to play a role in disease aetiology, progression and outcome. Previous studies have revealed autosomal epigenetic differences between males and females in some tissues, including differences in DNA methylation patterns. Here, we report for the first time an analysis of autosomal sex differences in DNAme using the Illumina EPIC array in human whole blood by performing a discovery (n = 1171) and validation (n = 2471) analysis.

RESULTS

We identified and validated 396 sex-associated differentially methylated CpG sites (saDMPs) with the majority found to be female-biased CpGs (74%). These saDMP's are enriched in CpG islands and CpG shores and located preferentially at 5'UTRs, 3'UTRs and enhancers. Additionally, we identified 266 significant sex-associated differentially methylated regions overlapping genes, which have previously been shown to exhibit epigenetic sex differences, and novel genes. Transcription factor binding site enrichment revealed enrichment of transcription factors related to critical developmental processes and sex determination such as SRY and ESR1.

CONCLUSION

Our study reports a reliable catalogue of sex-associated CpG sites and elucidates several characteristics of these sites using large-scale discovery and validation data sets. This resource will benefit future studies aiming to investigate sex specific epigenetic signatures and further our understanding of the role of DNA methylation in sex differences in human whole blood.

Concentrations of per- and polyfluoroalkyl substances (PFAS) in human placental tissues and associations with birth outcomes

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants commonly detected in human serum. Previous studies have observed associations between maternal serum PFAS and adverse pregnancy and birth outcomes such as lower birth weight or pre-eclampsia; however, few studies have explored these associations with birth outcomes and placental tissue PFAS concentration. The placenta is a vital contributor to a healthy pregnancy and may be involved in the mechanism of PFAS reproductive toxicity. Our goal was to measure placental PFAS concentrations and examine associations with birth outcomes (e.g., birth weight, gestational duration). Placenta samples (n = 120) were collected during delivery from women enrolled in the Healthy Pregnancy, Healthy Baby cohort (HPHB) in Durham, North Carolina. All placenta samples contained detectable PFAS, with perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) being the most abundant and most frequently detected (all >96% detection frequency). While placental PFAS concentrations did not differ by infant sex, higher PFAS levels were observed in placenta from nulliparous women, suggesting that parity influences the accumulation of PFAS in the placenta. We used linear regression models to examine associations between placental PFAS and birth outcomes. After adjustment for parity, tobacco use, maternal age, and maternal race, we found that placental PFOS was associated with lower birth weight for gestational age in male infants and higher birth weight for gestational age in female infants. Similar findings were seen for PFNA for birth weight for gestational age. These differences in birth outcomes based on infant sex highlight a need to explore mechanistic differences in PFAS toxicity during gestation for male and female infants.

Differential placental CpG methylation is associated with chronic lung disease of prematurity

BACKGROUND

Chronic lung disease (CLD) is the most common pulmonary morbidity in extremely preterm infants. It is unclear to what extent prenatal exposures influence the risk of CLD. Epigenetic variation in placenta DNA methylation may be associated with differential risk of CLD, and these associations may be dependent upon sex.

METHODS

Data were obtained from a multi-center cohort of infants born extremely preterm (<28 weeks' gestation) and an epigenome-wide approach was used to identify associations between placental DNA methylation and CLD (n = 423). Associations were evaluated using robust linear regression adjusting for covariates, with a false discovery rate of 0.05. Analyses stratified by sex were used to assess differences in methylation-CLD associations.

RESULTS

CLD was associated with differential methylation at 49 CpG sites representing 46 genes in the placenta. CLD was associated with differential methylation of probes within genes related to pathways involved in fetal lung development, such as p53 signaling and myo-inositol biosynthesis. Associations between CpG methylation and CLD differed by sex.

CONCLUSIONS

Differential placental methylation within genes with key roles in fetal lung development may reflect complex cell signaling between the placenta and fetus which mediate CLD risk. These pathways appear to be distinct based on fetal sex.

IMPACT

In extremely preterm infants, differential methylation of CpG sites within placental genes involved in pathways related to cell signaling, oxidative stress, and trophoblast invasion is associated with chronic lung disease of prematurity. DNA methylation patterns associated with chronic lung disease were distinctly based on fetal sex, suggesting a potential mechanism underlying dimorphic phenotypes. Mechanisms related to fetal hypoxia and placental myo-inositol signaling may play a role in fetal lung programming and the developmental origins of chronic lung disease. Continued research of the relationship between the placental epigenome and chronic lung disease could inform efforts to ameliorate or prevent this condition.

Gender differences in the association between environment and psychosis

Various environmental exposures have been associated with psychosis spectrum disorder. However, the role of gender in this association has received little attention. Therefore, we conducted a systematic review to evaluate gender-related differences and identified 47 research articles investigating the associations of psychosis with childhood adversity, substance use, urbanicity, migration, season of birth, and obstetric complication in the PubMed database. The findings suggest that childhood abuse may be more strongly associated with a risk to develop psychosis and an earlier age at onset of illness in women than in men. Furthermore, childhood adversity has been associated with the severity of different symptom dimensions in men and women. Growing up in an urban environment and immigration are more strongly associated with psychosis risk in men than in women. Despite a higher prevalence of substance abuse comorbidity in men diagnosed with psychotic disorders, it appears that the association between substance use and psychosis risk may be stronger in women. These findings should be evaluated with caution considering several methodological limitations, limited number of studies, and lack of consistency across results. Overall, although further investigation is needed, our review shows that gender-related differences in the associations of environmental exposures with psychosis expression may exist.

Prenatal Choline Supplementation Alters One Carbon Metabolites in a Rat Model of Periconceptional Alcohol Exposure

Prenatal alcohol exposure disturbs fetal and placental growth and can alter DNA methylation (DNAm). Supplementation with the methyl donor choline can increase fetal and placental growth and restore DNAm, suggesting converging effects on one-carbon metabolism (1CM). We investigated the impact of periconceptional ethanol (PCE) exposure and prenatal choline supplementation on 1CM in maternal, placental, and fetal compartments. Female Sprague Dawley rats were given a liquid diet containing 12.5% ethanol (PCE) or 0% ethanol (control) for 4 days before and 4 days after conception. Dams were then placed on chow with different concentrations of choline (1.6 g, 2.6 g, or 7.2 g choline/kg chow). Plasma and tissues were collected in late gestation for the analysis of 1CM components by means of mass spectrometry and real-time PCR. PCE reduced placental components of 1CM, particularly those relating to folate metabolism, resulting in a 3−7.5-fold reduction in the ratio of s-adenosylmethionine:s-adenosylhomocysteine (SAM:SAH) (p < 0.0001). Choline supplementation increased placental 1CM components and the SAM:SAH ratio (3.5−14.5-fold, p < 0.0001). In the maternal and fetal compartments, PCE had little effect, whereas choline increased components of 1CM. This suggests that PCE impairs fetal development via altered placental 1CM, highlighting its role in modulating nutritional inputs to optimize fetal development.

Placental Abnormalities are Associated With Specific Windows of Embryo Culture in a Mouse Model

Assisted Reproductive Technologies (ART) employ gamete/embryo handling and culture in vitro to produce offspring. ART pregnancies have an increased risk of low birth weight, abnormal placentation, pregnancy complications, and imprinting disorders. Embryo culture induces low birth weight, abnormal placental morphology, and lower levels of DNA methylation in placentas in a mouse model of ART. Whether preimplantation embryos at specific stages of development are more susceptible to these perturbations remains unresolved. Accordingly, we performed embryo culture for several discrete periods of preimplantation development and following embryo transfer, assessed fetal and placental outcomes at term. We observed a reduction in fetal:placental ratio associated with two distinct windows of preimplantation embryo development, one prior to the morula stage and the other from the morula to blastocyst stage, whereas placental morphological abnormalities and reduced imprinting control region methylation were only associated with culture prior to the morula stage. Extended culture to the blastocyst stage also induces additional placental DNA methylation changes compared to embryos transferred at the morula stage, and female concepti exhibited a higher loss of DNA methylation than males. By identifying specific developmental windows of susceptibility, this study provides a framework to optimize further culture conditions to minimize risks associated with ART pregnancies.

Sex-specific placental gene expression signatures of small for gestational age at birth

INTRODUCTION

Small for gestational age at birth (SGA), often a consequence of placental dysfunction, is a risk factor for neonatal morbidity and later life cardiometabolic diseases. There are sex differences in placental gene expression and fetal growth. Here, we investigated sex-specific associations between gene expression in human placenta measured using RNA sequencing and SGA status using data from ethnic diverse pregnant women in the NICHD Fetal Growth Studies cohort (n = 74).

METHODS

Gene expression measures were obtained using RNA-Sequencing and differential gene expression between SGA (birthweight <10th percentile) and appropriate for gestational age (AGA: ≥10th and <90th percentile) was tested separately in males (12 SGA and 27 AGA) and females (9 SGA and 26 AGA) using a weighted mean of log ratios method with adjustment for mode of delivery and ethnicity.

RESULTS

At 5% false discovery rate (FDR), we identified 40 differentially expressed genes (DEGs) related to SGA status among males (95% up- and 5% down-regulated) and 314 DEGs among females (32.5% up- and 67.5% down-regulated). Seven female-specific DEGs overlapped with known imprinted genes (AXL, CYP24A1, GPR1, PLAGL1, CMTM1, DLX5, LY6D). The DEGs in males were significantly enriched for immune response and inflammation signaling pathways whereas the DEGs in females were enriched for organ development signaling pathways (FDR<0.05). Sex-combined analysis identified no additional DEGs, rather 98% of the sex-specific DEGs were no longer significant and the remaining 2% were attenuated.

DISCUSSION

This study revealed sex-specific human placental gene expression changes and molecular pathways associated with SGA and underscored that unravelling the pathogenesis of SGA warrants consideration of fetal sex as a biological variable.

TRIAL REGISTRATION

https://www.

CLINICALTRIALS

gov, Unique identifier: NCT00912132.

Extreme prematurity: Risk and resiliency

Individuals born extremely preterm (before 28 weeks of gestation) comprise only about 0.7% of births in the United States and an even lower proportion in other high resource countries. However, these individuals account for a disproportionate number of children with cerebral palsy, intellectual deficit, autism spectrum disorder, attention deficit hyperactivity disorder, and epilepsy. This review describes two large multiple center cohorts comprised of individuals born extremely preterm: the EPICURE cohort, recruited 1995 in the United Kingdom and the Republic of Ireland, and the Extremely Low Gestational Age Newborn (ELGAN), recruited 2002-2004 in five states in the United States. The primary focus of these studies has been neurodevelopmental disorders, but also of interest are growth, respiratory illness, and parent- and self-reported global health and well-being. Both of these studies indicate that among individuals born extremely preterm the risks of most neurodevelopmental disorders are increased. Early life factors that contribute to this risk include perinatal brain damage, some of which can be identified using neonatal head ultrasound, bronchopulmonary dysplasia, and neonatal systemic inflammation. Prenatal factors, particularly the family's socioeconomic position, also appear to contribute to risk. For most adverse outcomes, the risk is higher in males. Young adults born extremely preterm who have neurodevelopmental impairment, as compared to those without such impairment, rate their quality of life lower. However, young adults born extremely preterm who do not have neurodevelopmental impairments rate their quality of life as being similar to that of young adults born at term. Finally, we summarize the current state of interventions designed to improve the life course of extremely premature infants, with particular focus on efforts to prevent premature birth and on postnatal efforts to prevent adverse neurodevelopmental outcomes.

Meta-analysis of epigenome-wide association studies in newborns and children show widespread sex differences in blood DNA methylation

BACKGROUND

Among children, sex-specific differences in disease prevalence, age of onset, and susceptibility have been observed in health conditions including asthma, immune response, metabolic health, some pediatric and adult cancers, and psychiatric disorders. Epigenetic modifications such as DNA methylation may play a role in the sexual differences observed in diseases and other physiological traits.

METHODS

We performed a meta-analysis of the association of sex and cord blood DNA methylation at over 450,000 CpG sites in 8438 newborns from 17 cohorts participating in the Pregnancy And Childhood Epigenetics (PACE) Consortium. We also examined associations of child sex with DNA methylation in older children ages 5.5-10 years from 8 cohorts (n = 4268).

RESULTS

In newborn blood, sex was associated at Bonferroni level significance with differences in DNA methylation at 46,979 autosomal CpG sites (p < 1.3 × 10-7) after adjusting for white blood cell proportions and batch. Most of those sites had lower methylation levels in males than in females. Of the differentially methylated CpG sites identified in newborn blood, 68% (31,727) met look-up level significance (p < 1.1 × 10-6) in older children and had methylation differences in the same direction.

CONCLUSIONS

This is a large-scale meta-analysis examining sex differences in DNA methylation in newborns and older children. Expanding upon previous studies, we replicated previous findings and identified additional autosomal sites with sex-specific differences in DNA methylation. Differentially methylated sites were enriched in genes involved in cancer, psychiatric disorders, and cardiovascular phenotypes.

Maternal Intake of Probiotics to Program Offspring Health

PURPOSE OF REVIEW

Probiotics intake may be considered beneficial by prospective and pregnant mothers, but their effects on offspring development are incompletely understood. The purpose of this review was to examine recent pre-clinical and clinical studies to understand how maternal probiotics exposure affects offspring health outcomes.

RECENT FINDINGS

Effects were investigated in the context of supporting offspring growth, intestinal health, and gut microbiota, preventing allergic diseases, supporting neurodevelopment, and preventing metabolic disorders in pre-clinical and clinical studies. Most human studies focused on infancy outcomes, whereas pre-clinical studies also examined outcomes at adolescence and young adulthood. While still understudied, both pre-clinical and clinical studies propose epigenetic modifications as an underlying mechanism. Optimal timing of intervention remains unclear. Administration of selected probiotics to mothers has programming potential for sustaining life-long health of offspring. Administration protocols, specific windows of susceptibility, and individual-specific responses need to be further studied.

Maternal vitamin D and offspring fracture risk: the Vitamin D in Pregnancy study

Vitamin D is important for bone health and strength. Previous studies report 25-hydroxyvitamin D (25(OH)D) exposure during pregnancy may impact offspring bone health later in life. In this study, maternal 25(OH)D at recruitment was associated with a lower fracture risk in boys and an increased fracture risk in girls at 28-32 weeks gestation.

PURPOSE

Maternal 25-hydroxyvitamin D (25(OH)D) in pregnancy has been shown to be associated with offspring bone measures in some studies, but few have examined fracture risk. We aimed to determine associations between maternal vitamin D status and offspring fracture risk.

METHODS

In total, 475 mother-child pairs participating in the Vitamin D in Pregnancy study in southeastern Australia were recruited. Maternal serum samples were taken at recruitment (< 16 weeks gestation) and/or 28-32 weeks gestation and analysed for 25(OH)D. Incident fractures in children were ascertained from date of birth (2002-2004) until December 31, 2012. Cox proportional hazard models included maternal age at recruitment, offspring sex, birth weight, gestation length and season of vitamin D sample.

RESULTS

Complete follow-up data were available for 400 children (median age = 9.5 years). There were 68 (17.0%) children who sustained at least one fracture. Higher maternal 25(OH)D (per 10 nmol/L) in early gestation was weakly associated with a decreased fracture risk in boys (HR 0.82; 95% CI 0.68, 0.99; p = 0.048) but not girls (HR 1.10; 95% CI 0.98, 1.25; p = 0.11). At late gestation, higher maternal 25(OH)D was associated with increased fracture risk in girls (HR 1.11; 95% CI 1.01, 1.23; p = 0.038) but not boys (HR 0.94; 95% CI 0.80, 1.10; p = 0.42). No statistically significant relationships were detected in analyses investigating 25(OH)D as a categorical variable.

CONCLUSION

There is some evidence that higher maternal 25(OH)D at recruitment was associated with lower fracture risk in boys, while higher maternal 25(OH)D at 28-32 weeks gestation was associated with an increased fracture risk in girls.

The Placenta's Role in Sexually Dimorphic Fetal Growth Strategies

Fetal sex affects the risk of pregnancy complications and the long-term effects of prenatal environment on health. Some have hypothesized that growth strategies differ between the sexes, whereby males prioritize growth whereas females are more responsive to their environment. This review evaluates the role of the placenta in such strategies, focusing on (1) mechanisms underlying sexual dimorphism in gene expression, (2) the nature and extent of sexual dimorphism in placental gene expression, (3) sexually dimorphic responses to nutrient supply, and (4) sexual dimorphism in morphology and histopathology. The sex chromosomes contribute to sex differences in placental gene expression, and fetal hormones may play a role later in development. Sexually dimorphic placental gene expression may contribute to differences in the prevalence of complications such as preeclampsia, although this link is not clear. Placental responses to nutrient supply frequently show sexual dimorphism, but there is no consistent pattern where one sex is more responsive. There are sex differences in the prevalence of placental histopathologies, and placental changes in pregnancy complications, but also many similarities. Overall, no clear patterns support the hypothesis that females are more responsive to the maternal environment, or that males prioritize growth. While male fetuses are at greater risk of a variety of complications, total prenatal mortality is higher in females, such that males exposed to early insults may be more likely to survive and be observed in studies of adverse outcomes. Going forward, robust statistical approaches to test for sex-dependent effects must be more widely adopted to reduce the incidence of spurious results.

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.

In search of sex-related mediators of affective illness

Sex differences in the rates of affective disorders have been recognized for decades. Studies of physiologic sex-related differences in animals and humans, however, have generally yielded little in terms of explaining these differences. Furthermore, the significance of these findings is difficult to interpret given the dynamic, integrative, and highly context-dependent nature of human physiology. In this article, we provide an overview of the current literature on sex differences as they relate to mood disorders, organizing existing findings into five levels at which sex differences conceivably influence physiology relevant to affective states. These levels include the following: brain structure, network connectivity, signal transduction, transcription/translation, and epigenesis. We then evaluate the importance and limitations of this body of work, as well as offer perspectives on the future of research into sex differences. In creating this overview, we attempt to bring perspective to a body of research that is complex, poorly synthesized, and far from complete, as well as provide a theoretical framework for thinking about the role that sex differences ultimately play in affective regulation. Despite the overall gaps regarding both the underlying pathogenesis of affective illness and the role of sex-related factors in the development of affective disorders, it is evident that sex should be considered as an important contributor to alterations in neural function giving rise to susceptibility to and expression of depression.

Differences in Glycolysis and Mitochondrial Respiration between Cytotrophoblast and Syncytiotrophoblast In-Vitro: Evidence for Sexual Dimorphism

In the placenta the proliferative cytotrophoblast cells fuse into the terminally differentiated syncytiotrophoblast layer which undertakes several energy-intensive functions including nutrient uptake and transfer and hormone synthesis. We used Seahorse glycolytic and mitochondrial stress tests on trophoblast cells isolated at term from women of healthy weight to evaluate if cytotrophoblast (CT) and syncytiotrophoblast (ST) have different bioenergetic strategies, given their different functions. Whereas there are no differences in basal glycolysis, CT have significantly greater glycolytic capacity and reserve than ST. In contrast, ST have significantly higher basal, ATP-coupled and maximal mitochondrial respiration and spare capacity than CT. Consequently, under stress conditions CT can increase energy generation via its higher glycolytic capacity whereas ST can use its higher and more efficient mitochondrial respiration capacity. We have previously shown that with adverse in utero conditions of diabetes and obesity trophoblast respiration is sexually dimorphic. We found no differences in glycolytic parameters between sexes and no difference in mitochondrial respiration parameters other than increases seen upon syncytialization appear to be greater in females. There were differences in metabolic flexibility, i.e., the ability to use glucose, glutamine, or fatty acids, seen upon syncytialization between the sexes with increased flexibility in female trophoblast suggesting a better ability to adapt to changes in nutrient supply.

Gestational blood levels of toxic metal and essential element mixtures and associations with global DNA methylation in pregnant women and their infants

BACKGROUND

Pregnant women and their fetuses are exposed to multiple toxic metals that together with variations in essential element levels may alter epigenetic regulation, such as DNA methylation.

OBJECTIVES

The aim of the study was to investigate the associations between gestational levels of toxic metals and essential elements and mixtures thereof, with global DNA methylation levels in pregnant women and their newborn children.

METHODS

Using 631 mother-child pairs from a prospective birth cohort (The Norwegian Mother, Father and Child Cohort Study), we measured maternal blood concentration (gestation week ~18) of five toxic metals and seven essential elements. We investigated associations as individual exposures and two-way interactions, using elastic net regression, and total mixture, using quantile g-computation, with blood levels of 5-methylcytocine (5mC) and 5-hydroxymethylcytosine (5hmC) in mothers during pregnancy and their newborn children (cord blood). Multiple testing was adjusted for using the Benjamini and Hochberg false discovery rate (FDR) approach.

RESULTS

The most sensitive marker of DNA methylation appeared to be 5mC levels. In pregnant mothers, elastic net regression indicated associations between 5mC and selenium and lead (non-linear), while in newborns results indicated relationships between maternal selenium, cobalt (non-linear) and mercury and 5mC, as well as copper (non-linear) and 5hmC levels. Several possible two-way interactions were identified (e.g. arsenic and mercury, and selenium and maternal smoking in newborns). None of these findings met the FDR threshold for multiple testing. No net effect was observed in the joint (mixture) exposure-approach using quantile g-computation.

CONCLUSION

We identified few associations between gestational levels of several toxic metals and essential elements and global DNA methylation in pregnant mothers and their newborn children. As DNA methylation dysregulation might be a key mechanism in disease development and thus of high importance for public health, our results should be considered as important candidates to investigate in future studies.

Gestational Cd Exposure in the CD-1 Mouse Induces Sex-Specific Hepatic Insulin Insensitivity, Obesity, and Metabolic Syndrome in Adult Female Offspring

There is compelling evidence that developmental exposure to toxic metals increases risk for obesity and obesity-related morbidity including cardiovascular disease and type 2 diabetes. To explore the hypothesis that developmental Cd exposure increases risk of obesity later in life, male, and female CD-1 mice were maternally exposed to 500 ppb CdCl2 in drinking water during a human gestational equivalent period (gestational day 0-postnatal day 10 [GD0-PND10]). Hallmark indicators of metabolic disruption, hepatic steatosis, and metabolic syndrome were evaluated prior to birth through adulthood. Maternal blood Cd levels were similar to those observed in human pregnancy cohorts, and Cd was undetected in adult offspring. There were no observed impacts of exposure on dams or pregnancy-related outcomes. Results of glucose and insulin tolerance testing revealed that Cd exposure impaired offspring glucose homeostasis on PND42. Exposure-related increases in circulating triglycerides and hepatic steatosis were apparent only in females. By PND120, Cd-exposed females were 30% heavier with 700% more perigonadal fat than unexposed control females. There was no evidence of dyslipidemia, steatosis, increased weight gain, nor increased adiposity in Cd-exposed male offspring. Hepatic transcriptome analysis on PND1, PND21, and PND42 revealed evidence for female-specific increases in oxidative stress and mitochondrial dysfunction with significant early disruption of retinoic acid signaling and altered insulin receptor signaling consistent with hepatic insulin sensitivity in adult females. The observed steatosis and metabolic syndrome-like phenotypes resulting from exposure to 500 ppb CdCl2 during the pre- and perinatal period of development equivalent to human gestation indicate that Cd acts developmentally as a sex-specific delayed obesogen.

Let's Talk about Placental Sex, Baby: Understanding Mechanisms That Drive Female- and Male-Specific Fetal Growth and Developmental Outcomes

It is well understood that sex differences exist between females and males even before they are born. These sex-dependent differences may contribute to altered growth and developmental outcomes for the fetus. Based on our initial observations in the human placenta, we hypothesised that the male prioritises growth pathways in order to maximise growth through to adulthood, thereby ensuring the greatest chance of reproductive success. However, this male-specific “evolutionary advantage” likely contributes to males being less adaptable to shifts in the in-utero environment, which then places them at a greater risk for intrauterine morbidities or mortality. Comparatively, females are more adaptable to changes in the in-utero environment at the cost of growth, which may reduce their risk of poor perinatal outcomes. The mechanisms that drive these sex-specific adaptations to a change in the in-utero environment remain unclear, but an increasing body of evidence within the field of developmental biology would suggest that alterations to placental function, as well as the feto-placental hormonal milieu, is an important contributing factor. Herein, we have addressed the current knowledge regarding sex-specific intrauterine growth differences and have examined how certain pregnancy complications may alter these female- and male-specific adaptations.

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.

Exposure to toxic metals and per- and polyfluoroalkyl substances and the risk of preeclampsia and preterm birth in the United States: a review

Preeclampsia and preterm birth are among the most common pregnancy complications and are the leading causes of maternal and fetal morbidity and mortality in the United States. Adverse pregnancy outcomes are multifactorial in nature and increasing evidence suggests that the pathophysiology behind preterm birth and preeclampsia may be similar-specifically, both of these disorders may involve abnormalities in placental vasculature. A growing body of literature supports that exposure to environmental contaminants in the air, water, soil, and consumer and household products serves as a key factor influencing the development of adverse pregnancy outcomes. In pregnant women, toxic metals have been detected in urine, peripheral blood, nail clippings, and amniotic fluid. The placenta serves as a "gatekeeper" between maternal and fetal exposures, because it can reduce or enhance fetal exposure to various toxicants. Proposed mechanisms underlying toxicant-mediated damage include disrupted placental vasculogenesis, an up-regulated proinflammatory state, oxidative stressors contributing to prostaglandin production and consequent cervical ripening, uterine contractions, and ruptured membranes and epigenetic changes that contribute to disrupted regulation of endocrine and immune system signaling. The objective of this review is to provide an overview of studies examining the relationships between environmental contaminants in the US setting, specifically inorganic (eg, cadmium, arsenic, lead, and mercury) and organic (eg, per- and polyfluoroalkyl substances) toxicants, and the development of preeclampsia and preterm birth among women in the United States.

Prenatal tobacco smoke exposure and neurological impairment at 10 years of age among children born extremely preterm: a prospective cohort

OBJECTIVE

To determine the association between prenatal tobacco smoke exposure and neurological impairment at 10 years of age among children born extremely preterm (<28 weeks of gestation).

DESIGN

The Extremely Low Gestational Age Newborn (ELGAN) Study, a prospective cohort.

SETTING

Ten-year follow-up of extremely preterm infants born at 14 US hospitals between 2002 and 2004.

METHODS

Prenatal tobacco smoke exposure was defined as a mother's report at enrolment of active (i.e. maternal) and passive smoking during pregnancy. Poisson regression with generalized estimating equations was used. Models adjusted for mother's age, race/ethnicity, education, insurance, pre-pregnancy body mass index, US region, multiple gestation and infant's sex; and in sensitivity analysis, gestational age at delivery and clinical subtype of preterm birth, given their classification as intermediate and non-confounding variables.

MAIN OUTCOMES

Neurological impairment at 10 years, epilepsy, cerebral palsy and cognitive impairment.

RESULTS

Of 1200 ELGAN study survivors, 856 were assessed at 10 years of age with neurological outcomes, of whom 14% (118/856) had active tobacco exposure during pregnancy and 24% (207/852) had passive tobacco exposure. Compared with children who were not exposed prenatally to tobacco, children exposed to active tobacco use during pregnancy had a higher risk of epilepsy (14% versus 5%; adjusted relative risk: 1.68, 95% CI 1.45-1.92). This risk remained after adjustment for gestational age at delivery and clinical subtype of preterm birth. Prenatal tobacco smoke exposure was not associated with other assessed neurological outcomes, including cerebral palsy and multiple measures of cognitive impairment.

CONCLUSIONS

Among children born extremely preterm, prenatal active tobacco smoke exposure was associated with an increased risk of epilepsy at 10 years of life.

TWEETABLE ABSTRACT

Among infants born before 28 weeks of gestation, prenatal active tobacco smoke exposure was associated with an increased risk of epilepsy at 10 years of life.