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By Hannah Millington
Health Reporter
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A mother's weight before pregnancy could be linked to autism-like behaviors in her children.
This is the conclusion of a study by researchers at the University of Hawaiʻi at Mānoa, who found that obesity can trigger metabolic shifts that cause lasting epigenetic changes in a mother's eggs.
These changes are passed on to the developing embryo and affect genes involved in brain development, including "Homer1," a protein important for regulating synaptic signaling, learning, memory and response to neural activity.
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Obesity and autism spectrum disorder (ASD) rates are increasing worldwide (though for autism this could be because of increased awareness).
More than 2 in 5 adults (42.4 percent) are diagnosed as obese in the U.S., while 1 in 31 children and 1 in 45 adults are living with ASD across the country.
While ASD is not an illness—and just means people's brains work differently from others'—the researchers said their findings mark a "significant advancement" in understanding how early life factors can shape long-term brain development.
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Conducting experiments in mice models, the team detected increased levels of a specific Homer1 gene isoform that is known to interfere with neural connections—and is associated with behaviors linked to ASD—in male offspring of obese female mice.
"This work highlights how a mother's health prior to pregnancy, not just during gestation, can shape her child's brain development in profound ways," said paper author and epigeneticist professor Alika K. Maunakea in a statement.
"We were surprised to find that even without direct maternal contact after conception, these epigenetic imprints from the egg carried enough weight to alter behavior."
To isolate the effects of pre-pregnancy obesity away from those during gestation, the time between conception and birth, the researchers used an in vitro fertilization (IVF) and embryo transfer model. This approach allowed them to study early epigenetic programming more precisely.
Behavioral assessments of adolescent male mice revealed impaired social interactions and repetitive behaviors. These traits, which mirror characteristics of ASD, were linked to altered gene regulation in the brain, the researchers explained.
"In our study, we report that female offspring did not show the same behavioral changes seen in males, even though they were exposed to the exact same conditions. This aligns with what we see in the human population—autism is diagnosed more frequently in boys than girls," Maunakea told Newsweek.
"While our findings suggest a male-specific vulnerability, it's important to note that this doesn't mean females are unaffected. They may show different or subtler traits that weren't captured in our behavioral tests. Future studies will need to examine this more closely."
"By leveraging our institute's expertise in developmental biology, reproductive science and epigenetics we are beginning to understand how early-life programming can ripple through generations," said paper author and reproductive biologist professor Monika Ward in a statement.
The researchers say the findings may lead to early interventions, potentially even before conception. However, they hope future studies will explore nutritional or pharmacological therapeutic strategies that may reverse or mitigate these effects.
"Our findings suggest that the time before conception—when a woman's eggs are maturing—is a sensitive window for programming long-term brain development in children. While we don't yet know the exact timing in humans, egg development takes about 3–4 months, so that's a potential target window for intervention," Maunakea explained.
"We're talking about achievable things like improving nutrition, managing body weight, or addressing metabolic health well before pregnancy begins—not just during pregnancy. These steps could support healthier developmental outcomes without needing medication or medical procedures."
There is no single known 'cause' for autism, but research suggests it could develop from a combination of genetic and environmental factors.
"Brain scans show differences in the shape and structure of the brain in people with autism compared to in neurotypical development. Researchers do not know the exact cause of autism but are investigating a number of theories, including the links among heredity, genetics, and medical problems," the Autism Society website outlines.
"There has been misinformation about the cause of autism. It is not caused by vaccines or due to parenting style or nutrition."
"Autism is a form of neurodiversity, and many autistic individuals live rich, meaningful lives. Our aim is to understand the biology so that families and healthcare providers can make informed choices, not to eliminate or 'fix' autism," Maunakea explained.
While Maunakea also said obesity is "not a moral failing" and influenced by many factors, he added: "By identifying modifiable risk factors, like pre-conception metabolic health, we can empower women with knowledge and support rather than judgment."
Do you have a tip on a health story that Newsweek should be covering? Do you have a question about autism? Let us know via health@newsweek.com.
Update 08/18/25, 11:02 p.m. ET: This article was updated with additional comments from Alika Maunakea.
Reference
Allan, N. P., Torres, A., Corley, M. J., Yamamoto, B. Y., Balaan, C., Yamauchi, Y., Peres, R., Qin, Y., Khadka, V. S., Deng, Y., Ward, M. A., & Maunakea, A. K. (2025). Pre-Conception Maternal Obesity Confers Autism Spectrum Disorder-like Behaviors in Mice Offspring Through Neuroepigenetic Dysregulation. Cells, 14(15), 1201. https://doi.org/10.3390/cells14151201
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