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Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition, and its development results from a nuanced interplay of genetics and environment. Prospective parents often wonder about genetics and environment in autism – how much of autism is “in the genes” versus influenced by external factors. Decoding these family risk factors is crucial for understanding the likelihood of autism in a future child and what can be done to prepare. In this post, we break down the spectrum of autism’s presentations, the genetic and environmental contributions to autism risk, and how advances like whole-genome preimplantation genetic testing for autism risk can empower families in making informed decisions.

What Is Autism Spectrum Disorder (ASD)?

Autism Spectrum Disorder (ASD) is a broad term for a range of neurodevelopmental differences characterized by challenges in social interaction, communication, and behavior. It’s called a “spectrum” because symptoms and abilities can vary widely from person to person. One individual with ASD may be nonverbal and require substantial support, while another may have subtle social difficulties and be highly independent. In essence, ASD is not a single, uniform condition but an umbrella for diverse presentations of atypical development in language, socialization, and repetitive behaviors. According to the U.S. Centers for Disease Control and Prevention (CDC), about 1 in 44 children in the United States is diagnosed with an autism spectrum disorder, affecting families across all ethnic and socioeconomic backgrounds (What causes Autism?).

Genetic Factors in Autism Risk

Research over the past decades has made it clear that genetics plays a major role in autism. Scientists have identified hundreds of genes associated with the condition. In some cases, a specific genetic mutation or syndrome directly leads to autism characteristics. In about 30% of autism cases, doctors can pinpoint an identifiable genetic cause – such as a mutation in a specific gene or a chromosomal alteration (What causes Autism?). These are cases often linked to known genetic syndromes or rare mutations. For example, Fragile X syndrome and Rett syndrome are distinct genetic conditions that frequently present with autism-like features  (Genetic Testing for Autism, Intellectual Disability, and other Neurodevelopmental Disorders).

However, most cases of autism do not have a single identifiable genetic explanation. Instead, they are considered multifactorial, meaning they result from a combination of genetic predispositions and environmental factors.

It’s important to note that not all genetic contributions are inherited from parents. Some autism-related genetic changes are de novo mutations, which means they are new mutations that occur in the egg, sperm, or embryo. In fact, many children with autism have no family history of the condition – their autism can be traced to a spontaneous genetic variant that neither parent possesses. This is one reason autism can appear in a family with no prior cases and why having a family history increases risk but is not required for autism to occur.

Orchid provides prospective parents with the ability to screen embryos for a subset of known genetic forms of autism. By identifying these genetic factors early, families can make informed reproductive choices based on their genetic risks.

Environmental Influences on Autism Risk

While genes lay the groundwork, environmental influences also play a significant role in autism development. “Environmental” in this context refers to a broad range of non-genetic factors, especially those acting during prenatal development and around the time of birth. Researchers have been studying many such factors that might increase the likelihood of autism. It’s important to understand that no single environmental factor causes autism by itself; rather, certain conditions or exposures can add to the risk, especially in a child who is genetically susceptible (Environmental factors influencing the risk of autism - PMC). Here are some of the environmental risk factors that have been linked to autism:

• Prenatal and birth complications: Certain conditions during pregnancy and around birth correlate with greater autism prevalence (Environmental risk for autism, explained | The Transmitter: Neuroscience News and Perspectives). Examples include extreme prematurity (being born very early), low birth weight, and pregnancy-related issues such as maternal diabetes or high blood pressure. Complications like these could affect early brain development, thereby modestly increasing autism risk.
• Maternal infections and immune factors: Serious infections or immune system activations in the mother during pregnancy have been linked to a higher chance of autism in the child (Environmental risk for autism, explained | The Transmitter: Neuroscience News and Perspectives). For instance, research has noted that maternal flu with high fever or other significant illnesses during critical periods of pregnancy may influence the developing fetal brain. Maternal autoimmune conditions (where the mother’s immune system is overactive or attacks her own tissues) have also been associated with elevated autism risk in children. Scientists suspect that inflammatory molecules crossing the placenta could alter gene expression or neural development in the fetus.
• Prenatal exposure to certain substances: Exposure to high doses of certain drugs or toxins in utero can impact a baby’s neurodevelopment. A well-documented example is the medication valproate (valproic acid), an anti-seizure and mood-stabilizing drug. When mothers take valproate during pregnancy, studies have found an increased risk of autism and other developmental issues in their children (Environmental risk for autism, explained | The Transmitter: Neuroscience News and Perspectives). 

It’s crucial to emphasize that these environmental factors do not guarantee a child will have autism; they simply nudge the odds upward. Most children exposed to one or more of these factors will not develop autism, and many children with autism had none of these exposures. Autism likely arises when certain environmental stresses converge with a genetic predisposition in the same individual. Indeed, evidence indicates that no single prenatal or birth factor has more than a modest association with ASD on its own (Understanding Autism Spectrum Disorder: An evidence-based review of ASD risk factors, evaluation, and diagnosis - PMC). Instead, it’s the combination of risk factors that matters.

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