What Families Should Know About Autism Risk

Autism spectrum disorder (ASD) is a complex condition where genes interact with nutrition, health, and environment. Autism often runs in families, but genes alone don’t determine outcome.

Many linked genes are “susceptibility genes,” raising vulnerability without guaranteeing autism. How they are expressed depends partly on maternal health and exposures during pregnancy.

One protective step is taking prenatal vitamins with folic acid. A 2017 study found children of mothers who took folic acid before and early in pregnancy had about a 23% lower autism risk.

Because 40–60% of women carry gene differences that make it harder to absorb folate, some may need higher- dose or methylated forms. Folate is critical for DNA and brain development.

Vitamin D shows similar patterns, with studies linking low maternal or newborn vitamin D levels to higher autism risk. Since up to 40% of people have gene types that limit vitamin D absorption, higher doses may also be needed. Vitamin D is important for both brain and immune health and helps regulate inflammation. Doctors can order tests to check individual needs.

Maternal health also matters. When mothers begin pregnancy overweight or with diabetes, the body is already under stress and inflammation. Research shows children of mothers with obesity or gestational diabetes have a 40–50% higher autism risk.

Both conditions have more than doubled since the 1980s. In Hawaiʻi, Native Hawaiian and Pacific Islander women have 1.5 times the odds of gestational diabetes compared to white women; nearly half are overweight or obese at conception.

Environmental toxins (air pollution (particularly (PM₂.₅,) industrial chemicals, and pesticides) have also been linked with autism risk.

Some people carry gene differences that make it harder to clear these toxins. Nationally, PM₂.₅ levels have fallen 40% since 2000, but wildfire smoke has since erased about a quarter of that progress.

Hawaiʻi’s averages are low, yet vog and wildfires – including the 2023 Maui fires – create spikes in pollution levels. Studies have shown consistent links between pesticide exposure and autism, with one study showing that mothers who lived with 1.2 miles of an area with heavy pesticide use had 10–20% higher odds of having a child with autism.

Reported autism rates have climbed sharply over the past three decades. Some of this is due to broader definitions, reclassifying children with speech delay or learning challenges to ASD, and greater awareness.

Researchers also note that families often seek an ASD diagnosis because it provides access to individualized therapy and specialized school support. Altogether, this may explain why, in Hawaiʻi public schools, students receiving autism services rose 29% in five years, from 2,088 in 2019 to 2,686 in 2024.

Still, rising rates of obesity and diabetes, pesticide use, and wildfire smoke suggest that real increases may also be occurring.

As autism has many influences, prevention needs a broad approach: take prenatal vitamins with folic acid, keep weight and blood glucose in a healthy range, get enough vitamin D, and limit exposure to pollution and pesticides when possible.

Genes can’t be changed, but lifestyle choices can help lower risk.

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