Summary:
A new study in mice reveals that maternal immune activation during a precise gestational window triggers autism-like developmental disruptions exclusively in male fetuses. Researchers traced this vulnerability to damaged spongiotrophoblast cells in the placenta, suggesting that placental immune tolerance failures, occurring before brain sexual differentiation, help explain the pronounced male bias in autism spectrum disorder.
Key Facts:
- Critical 24-Hour Window: Maternal immune activation at embryonic day 12.5 caused developmental abnormalities in approximately one-third of exposed fetuses within just 24 hours, marking the earliest observed signs of disruption following maternal inflammation.
- Exclusive Male Susceptibility: Across all experimental trials, autism-like developmental traits emerged only in male fetuses, while female fetuses developed normally despite experiencing the same inflammatory maternal environment.
- Placental Barrier Breakdown: The male-specific vulnerability was tied to structural and functional impairment of spongiotrophoblasts, specialized placental border cells that normally maintain maternal-fetal immune tolerance.
Source: Cold Spring Harbor Laboratory (CSHL)
While genetic predisposition accounts for a significant portion of autism spectrum disorder (ASD) liability, maternal environmental conditions during pregnancy represent a well-recognized contributing factor. Among these environmental triggers, maternal immune activation (MIA), such as an inflammatory reaction driven by a viral or bacterial infection, has consistently been correlated with elevated neurodevelopmental risk.
However, precisely how maternal inflammatory cascades breach fetal defenses, why only a subset of pregnancies are affected, and why autism is diagnosed roughly four times more frequently in males than females remain longstanding questions in developmental neuroscience.
In a new study, investigators at Cold Spring Harbor Laboratory (CSHL) demonstrate that the primary interface of this interaction may lie outside the brain entirely. By examining gestational inflammation at high temporal resolution, researchers found that maternal immune activation alters development by damaging crucial cells within the placenta, producing developmental disruptions exclusive to male offspring.
“To truly understand autism spectrum disorder, we have to look beyond the brain,” said Lucas Cheadle, Ph.D., Associate Professor at CSHL and senior author of the study. “Our work suggests that maternal immune activation and changes within the placenta are a gateway to autism for some unique individuals.”
A Critical Window for Gestational Disruption
To dissect the timing of vulnerability, Cheadle’s research team simulated viral immune challenges at multiple discrete stages of mouse pregnancy using an immune-activating mimetic that triggers inflammatory pathways without causing live viral infection.
The investigators pinpointed embryonic day 12.5 (E12.5) as the critical vulnerability window. At this developmental juncture, approximately one-third of the fetuses exhibited signs of altered development within just 24 hours following maternal immune stimulation.
“While maternal immune activation has been studied for a long time, this is the earliest that scientists have ever seen signs of disruption,” noted Irene Sanchez Martin, Ph.D., a postdoctoral fellow in the Cheadle lab and co-investigator on the study.
Pre-Hormonal Male Vulnerability
Strikingly, across all cohorts, only male mouse fetuses developed autism-like abnormalities. Female littermates subjected to the exact same maternal inflammatory event developed normally.
Because this divergence manifests at E12.5, it challenges traditional hypotheses that sex differences in autism risk are primarily driven by sex steroid surges during late gestation or postnatal life.
“It’s really fascinating, because we’re looking at an age which precedes hormonal surges,” Dr. Cheadle explained. “It precedes sexual differentiation in the brain and many other regions. So, it’s surprising there would be a sex-based difference this early.”
Spongiotrophoblasts: The Placental Fault Line
Seeking the biological driver underlying why only certain male fetuses were susceptible, the team examined the placenta—the shared vascular organ governing fetal nutrition, gas exchange, and immunological protection.
They focused on spongiotrophoblasts, specialized placental cells located at the junction where maternal tissue and fetal cells interface. In normally developing pups, this junction remained intact and healthy. Conversely, in male fetuses exhibiting developmental alterations, the spongiotrophoblasts displayed clear signs of cellular damage.
Under basal conditions, spongiotrophoblasts act as an immunological shield, actively signaling maternal immune cells to tolerate the semi-allogeneic fetus. Following maternal inflammation, however, these cells lost their barrier-protective properties, permitting maternal immune responses to negatively affect fetal development.
The findings suggest male embryos may express distinct surface antigens or molecular cues that provoke an adverse maternal immune reaction during systemic inflammation. Conversely, female fetuses appear equipped with intrinsic protective mechanisms that preserve placental integrity.
“A protective mechanism may exist within the female that could be harnessed to help the male,” Cheadle stated. “We’re trying to understand how autism emerges in both sexes. The evidence says that there are potentially different mechanisms.”
The Cheadle laboratory is currently analyzing the distinct molecular pathways active in male versus female placental cells during maternal immune activation. Uncovering how female placentas withstand maternal inflammation could highlight novel therapeutic targets to protect vulnerable fetuses and open pathways for earlier clinical intervention.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this Autism Research:
- Media Contact: Gina DiPietro
- Source: CSHL
- Image Credit: Image credited to Cheadle lab/CSHL
- Original Research is Open Access: Science Advances (September 16, 2026). “Maternal-fetal immune conflict contributes to male-specific impairments in a mouse model of neurodevelopmental disorders” Authors: Irene Sanchez-Martin, Bharti Kukreja, Paige Henderson, Qianyu Lin, Daniel DiMartino, Valerie Bagan, Justin Park, Brian T. Kalish, and Lucas Cheadle.
- DOI: 10.1126/sciadv.aeg0779
Abstract
Maternal-fetal immune conflict contributes to male-specific impairments in a mouse model of neurodevelopmental disorders
Autism spectrum disorder (ASD) arises from genetic and environmental risk factors. One environmental factor, maternal immune activation (MIA)—in which pathogenic infection during pregnancy increases ASD risk in offspring—disproportionately affects males. However, the basis for this male-specific vulnerability and the mechanisms by which inflammatory signals cross the maternal-fetal interface to affect the male embryo remain largely unknown.
Using the poly(I:C) mouse model of neurodevelopmental disorders, we characterize fetal, placental, and amniotic changes occurring within 24 hours of MIA. We find that 30% of embryos exhibit large-scale teratogenic abnormalities—ranging from decreased fetal weight to altered sensory organ development—while 70% develop normally.
These abnormalities occur exclusively in a subset of males, never in females. Single-nucleus transcriptomics revealed robust induction of proinflammatory gene programs in the placentas of affected males across a broad range of cell types, and most prominently in spongiotrophoblasts—fetally derived cells that partly form the maternal-fetal border.
These cells simultaneously down-regulate extracellular matrix and hormone biosynthesis pathways, coinciding with a breakdown in placental structural integrity and the accumulation of immune cells and cytokines in the amniotic fluid. One such cytokine, interleukin-6, is required for MIA-evoked developmental abnormalities to emerge.
Our data indicate that MIA drives a rapid shift from an immunosuppressive to a proinflammatory maternal-fetal interface in a vulnerable subset of male embryos, producing acute, sex-restricted developmental deficits.
We propose that male embryos may express unique proteins capable of triggering this inflammatory response, which—combined with MIA-induced loss of maternal immunosuppression—selectively derails male embryonic development.
