Maternal blood cell-free DNA methylation provides a minimally invasive research window into prenatal epigenetic features associated with late-stage autism diagnosis and may support future biomarker and early intervention studies.
WGBS of cfDNA in a prospective autism cohort study enables prenatal detection of ASD-associated differentially methylated regions (DMRs). This experimental diagram details the process of selecting study participants for cfDNA sampling, subsequent diagnostic follow-up, and computational methods for interrogating WGBS data for DMRs related to ASD diagnosis. Williams, L. (2026)
In recent research, communication biology We investigated whether cell-free DNA (cfDNA) methylation patterns in maternal blood can help identify prenatal epigenomic signatures associated with later autism spectrum disorder (ASD) diagnosis and maternal obesity.
The role of molecular and epigenetic markers in ASD
Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder among American children characterized by persistent deficits in social communication and restricted, repetitive behaviors. Its clinical manifestations and severity are highly variable. Children with ASD often have co-occurring conditions such as attention deficit disorder, obesity, epilepsy, anxiety, depression, and intellectual disability. Early behavioral intervention has the potential to improve outcomes, but progress is hampered by the lack of reliable early molecular markers to guide timely diagnosis and intervention.
ASD results from both genetic and environmental factors. Although high concordance rates in identical twins indicate a strong genetic component, ASD is polygenic and involves numerous rare and common mutations. Environmental exposures, particularly maternal obesity (MO), further modulate ASD risk through interactions with genetic susceptibility.
Epigenetic mechanisms, particularly DNA methylation, mediate the effects of environmental exposures such as MO on gene networks implicated in ASD. Methylation signatures associated with ASD have been identified in the human brain and placenta, and animal models have shown that MO-induced epigenetic changes in the developing brain can disrupt neurodevelopment and social behavior.
Human studies of early epigenetic markers of ASD remain limited by the lack of access to fetal tissues prior to clinical diagnosis. Recent advances in non-invasive prenatal testing have made it possible to analyze cfDNA from maternal blood. CffDNA derived from placental apoptosis increases in maternal plasma as pregnancy progresses and preserves the placental methylome profile, thus providing a non-invasive window into the fetal epigenome. Despite these advances, research on the prenatal cell-free DNA methylome is still constrained by low-resolution methods and limited sample sizes.
Examining the association between maternal prenatal cfDNA methylome, autism risk, and maternal obesity
The current study analyzed samples from the Autism Risk Markers-Early Learning Signs in Babies (MARBLES) cohort, a prospective study of women at high risk of having children with autism spectrum disorder (ASD).
Eligibility criteria included women who were pregnant or planning a pregnancy, who had a child previously diagnosed with ASD, and who might have a half-sibling of a child with ASD. Participants also had to be 18 years of age or older, fluent in English, and reside within 2.5 hours of the Davis/Sacramento area.
Mothers provided demographic, dietary, and medical data before and throughout pregnancy. Offspring were assessed for ASD symptoms at 6, 12, 24, and 36 months of age. Neurodevelopmental outcomes were determined using established algorithms based on Autism Diagnostic Observation Schedule (ADOS) and Mullen Scales of Early Learning (MSEL) scores.
Children classified as non-ASD included both neurotypical and atypical participants. For this analysis, only those with at least 1 ml of plasma available for cfDNA extraction were included.
Common epigenomic alterations in ASD and maternal obesity
A total of 51 pregnancies were selected to capture variation in fetal sex, maternal BMI, and ASD diagnosis. Maternal plasma cfDNA collected near delivery at 36–41 weeks of gestation was isolated and subjected to whole-genome bisulfite sequencing (WGBS) for single-nucleotide methylome analysis.
Examining the cfDNA methylome separately for each fetal sex identified differentially methylated regions (DMRs) associated with ASD that are particularly enriched in genes and pathways important for neurodevelopment. Of note, female pregnancies exhibited a greater number and magnitude of these DMRs than male pregnancies. Furthermore, the direction of methylation changes often differs between sexes, suggesting an underlying sex-specific epigenetic response.
ASD-associated DMRs were primarily found in gene regions and genomic regions enriched with cytosine-phosphate-guanine (CpG) sites, which are known to be important regulatory elements. Genes mapped to these regions were deeply involved in synaptic signaling, calcium signaling, and circadian entrainment, processes essential for normal brain development. Although both male and female DMR gene lists overlapped significantly with established autism risk genes, some female fetal fraction-adjusted analyzes showed lower enrichment of these risk genes. Furthermore, these DMRs are enriched at genomic loci that undergo dynamic methylation changes during pregnancy, highlighting their potential developmental relevance.
The methylation patterns observed in cfDNA were shown to substantially overlap with ASD-associated DMRs reported in matched term placental samples and unrelated postmortem cortical tissue. There was substantial overlap and convergence at the genetic level in the biological pathways affected across these different tissues and sexes, particularly in synaptic signaling pathways. Importantly, a core set of genes have been found to be differentially methylated across all tissues and sex groups, many of which play fundamental roles in neurodevelopment.
Specific DMRs were restricted to a female-specific list and included known ASD risk genes. MO DMRs (maternal obesity) in cfDNA were also enriched in ASD-related gene pathways, significantly overlapped with ASD DMRs in both sexes, and were commonly enriched in synaptic and neurodevelopmental pathways.
Pathway analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database demonstrated that both ASD-related and MO-related DMRs are concentrated in several key pathways, including calcium signaling, circadian entrainment, and synaptic transmission. Genes uniquely associated with MO DMRs were involved in neuromodulatory signaling, whereas genes uniquely associated with ASD DMRs were often associated with metabolic processes and motor protein function, suggesting both common and distinct biological mechanisms.
DMR genes shared by ASD and MO are clustered in neurodevelopmentally important pathways, highlighting convergent epigenetic mechanisms linking prenatal exposures and neurodevelopmental outcomes.
conclusion
The current study provides evidence that maternal plasma cfDNA reflects both common and distinct epigenomic signatures associated with ASD and maternal obesity. These findings support the possibility that common epigenetic pathways contribute to neurodevelopmental risk. Importantly, these results highlight the potential utility of cfDNA as a minimally invasive research tool for discovering early epigenetic changes associated with adverse neurodevelopmental outcomes and provide a framework for future studies of early detection and intervention.
However, the authors caution that the study was based on a small, risk-enriched cohort and was limited to maternal plasma samples from late third trimester. They also cannot determine whether the methylation differences arise from fetal or maternal cfDNA, and cfDNA does not provide a direct brain-specific resolution. Therefore, larger independent studies are needed to translate these findings into clinical screening and diagnosis.
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Reference magazines:
- L.A. Williams, E. Habibi, M. Miller, I. Hartz-Picciotto, CK Walker, RJ Schmidt, JM LaSalle (2026). Prenatal cell-free DNA methylome detects association with autism and maternal obesity. Communication biology. Press article. Doi: 10.1038/s42003-026-10500-9, https://www.nature.com/articles/s42003-026-10500-9
