A Blood Test in Late Pregnancy May Offer Early Clues to Autism Risk, Study Finds

A routine blood draw taken in the final weeks of pregnancy may one day carry hints about whether a child will go on to be diagnosed with autism, according to a new study that researchers describe as an early but meaningful step toward understanding the disorder’s biological origins before birth.The research, published in the journal Communications Biology, examined cell-free DNA — fragments of genetic material, much of it shed from the placenta, that circulate in a pregnant woman’s bloodstream. Scientists at University of California at Davis and partner institutions sequenced the full methylome of samples collected from 51 pregnancies between 36 and 41 weeks’ gestation, mapping the chemical tags that turn genes on and off without altering the DNA sequence itself.Specific methylation patterns lined up with which children later received an autism diagnosis by age three, and many of those same patterns overlapped with changes tied to maternal obesity, a long-suspected but poorly explained risk factor for the disorder.In other words, a single vial of a pregnant woman’s blood in her final trimester may already contain faint chemical footprints of how her baby’s brain is developing, footprints that, in this study, showed up more often in children later diagnosed with autism.A professor and molecular epidemiologist at UC Davis, Rebecca Schmidt, tells the New York Sun the findings offer a preliminary but real signal.“There might be markers associated with the child’s future neurodevelopmental outcomes, like autism, that can be found in maternal blood during late pregnancy,” Ms. Schmidt said.So, what does a finding like this actually change for doctors, and for the families waiting years for answers?Why The Blood Carries CluesScientists studying autism’s biological roots have long been stuck with a narrow problem: the tissue that matters most, fetal and placental cells from early development, is nearly impossible to study in a living child before symptoms emerge. Brain tissue can only be examined after death, and placental tissue is typically collected only at birth, after the developmental window in question has already closed.Cell-free DNA testing offers a workaround. The same fragments of placental genetic material already used in routine noninvasive prenatal screening for chromosomal conditions like Down syndrome also carry methylation marks that mirror fetal tissue activity. As pregnancy advances, a growing share of that circulating material comes from the placenta, providing researchers with a noninvasive readout of the gene-regulating environment of a developing fetus.The mothers in the cohort came from the Markers of Autism Risk in Babies — Learning Early Signs, a long-running project following families considered to be at elevated risk because they already had one child with autism. Researchers tracked each child’s development through clinical evaluations at six, 12, 24, and 36 months, then matched those outcomes to the methylation profiles drawn from maternal blood months earlier.The regions of the genome that stood out clustered around genes involved in synaptic signaling — the chemical communication between neurons that shapes how the brain wires itself — along with genes tied to calcium signaling and the body’s circadian clock. Many of those regions overlapped with autism-linked methylation patterns previously identified separately in placental and postmortem brain tissue.One unexpected finding involved sex differences. Methylation changes linked to autism were both more numerous and larger in pregnancies carrying female fetuses than male fetuses, and the direction of those changes often ran opposite between the sexes, a detail that lands amid a broader scientific effort to understand why boys are diagnosed with autism far more often than girls.In simple terms, girls and boys appear to process the same biological risk factors for autism in different ways, which may help explain why boys are diagnosed so much more often.Obesity’s Overlapping SignaturePerhaps the most consequential thread for expectant mothers involved weight. The study found that methylation changes associated with maternal obesity significantly overlapped with the same neurodevelopmental gene pathways disrupted in autism-linked samples, particularly those governing synaptic transmission, which is the process neurons use to send signals to one another as the brain develops. The dean of Emory University’s Rollins School of Public Health, Daniele Fallin, tells the Sun the connection between maternal metabolic health and fetal brain development deserves closer scrutiny, but not premature conclusions.“It is too soon to assume maternal obesity and autism share biological pathways,” Ms. Fallin said. “This work indicates that we should continue to ask questions about this connection.”Ms. Schmidt, who has studied the link between metabolic conditions and childhood autism, notes that the two may be tangled together through shared inflammatory or metabolic processes.“Maternal obesity and related metabolic conditions are risk factors for childhood autism,” she said. “Even though the biologic mechanisms of each condition are not fully understood, they are thought to involve overlapping pathways, such as inflammatory or metabolic pathways, that in turn shape brain development.”In simple terms, obesity during pregnancy and autism risk may be connected because both seem to disrupt some of the same chemical signals that guide how a baby’s brain develops.Not A Diagnostic Tool, YetMs. Fallin and Ms. Schmidt were emphatic that the findings should not change how expectant parents approach pregnancy or early childhood. The sample size was small, drawn entirely from families already considered at elevated familial risk, meaning the results may not generalize to the broader population of expectant mothers.Scientists also could not determine with certainty whether the methylation signals originated from fetal cells, placental cells, or the mother’s blood, and cell-free DNA testing cannot provide the brain-specific resolution needed to draw firm conclusions about what is unfolding in a developing fetal brain.Ms. Fallin describes the paper as discovery-stage science meant to sharpen future questions, not a message for the delivery room.“This paper is an intriguing preliminary discovery work. Its purpose is to prompt scientists to think creatively and dig deeper to understand how biological samples in pregnancy could inform what we know about how autism forms and what we can do to prevent the challenges people with autism face,” she said. “It is not yet an answer that should change anything about how we approach a healthy pregnancy or early child development.”Ms. Fallin also underscores that any path toward a usable screening tool runs through much larger studies.“This is a very small sample of mothers and their babies,” Ms. Fallin said. “The field needs to measure the same biosamples in additional studies that follow women during pregnancy and through the early years of the child’s life to see if these findings remain consistent across a larger number of people.”The chief science officer at Autism Speaks, Dr. Andy Shih, tells the Sun the study adds a data point to a far more complicated picture, not a standalone explanation.“Autism is caused by a complex interplay of genetic and environmental factors, and it is not likely to be explained by any single prenatal factor or biological mechanism,” Dr. Shih said. “While this study suggests an association between certain DNA methylation patterns during pregnancy, maternal obesity, and later autism diagnosis, the findings should be considered preliminary.” Dr. Shih also underscores that expectant parents with questions about their own risk factors should raise them directly with a doctor rather than draw conclusions from the study itself.Confirming the signal in a wider population, researchers say, is the next phase of research that needs to move beyond families already touched by autism.“Larger studies of pregnancies that are not at elevated familial likelihood of autism should examine epigenetic marks in prenatal blood that associate with later autism status of the child, and determine the overlap of specific markers and pathways,” Ms. Schmidt said.For now, scientists working in the field describe the study the same way: not a breakthrough, but a proof of concept: an early hint that the biological story behind autism may start to take shape long before delivery, detectable in nothing more than a routine vial of blood.If the signal holds up in larger, more diverse populations, it could eventually open the door to something obstetric medicine has never had: an early warning system for autism, drawn from a test expectant mothers already receive.“This is very far from a clinically relevant test,” Ms. Fallin added. “This is preliminary discovery work that should shape the next questions about what may cause autism and the challenges people with autism face.”

A Blood Test in Late Pregnancy May Offer Early Clues to Autism Risk, Study Finds

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