By Kenneth Williams-
A sweeping new study is raising urgent questions about the safety of commonly prescribed medications during pregnancy, after researchers uncovered a significant association between a broad class of drugs and the risk of autism spectrum disorder (ASD) in children.
Drawing on one of the largest datasets ever assembled in maternal-child health research, the findings signal what scientists describe as a critical public health concern—one that may reshape how medications are evaluated and prescribed during pregnancy.
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In a groundbreaking investigation published in Molecular Psychiatry, researchers from the University of Nebraska Medical Center (UNMC) analyzed an unprecedented 6.14 million maternal-child health records. The dataset, sourced from the Epic Cosmos database, represents nearly one-third of all births in the United States between 2014 and 2023—making it one of the most comprehensive analyses of prenatal exposure ever conducted.
Led by Karoly Mirnics, MD, PhD, dean and director of the Munroe-Meyer Institute, alongside lead author Eric Peeples, MD, PhD, the study took a novel approach to understanding medication-related risk. Rather than grouping drugs by their intended use—such as antidepressants or cardiovascular medications—the researchers categorized them based on their biochemical effects, specifically their ability to interfere with sterol biosynthesis, a pathway critical to cholesterol production.
This shift in methodology proved pivotal. By focusing on shared biological mechanisms rather than clinical indications, the team identified a striking and consistent pattern: medications that inhibit the cholesterol synthesis pathway—referred to as sterol biosynthesis–inhibiting medications (SBIMs)—were associated with higher rates of autism spectrum disorder in children exposed to them in utero.
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The implications are profound. Many of the medications included in the study are among the most widely prescribed in the United States, collectively accounting for more than 400 million prescriptions annually. These include drugs used to treat depression, anxiety, psychosis, and cardiovascular conditions—therapies that are often essential for maintaining maternal health.
Among the 15 medications analysed were aripiprazole, fluoxetine, sertraline, bupropion, trazodone, haloperidol, buspirone, and cariprazine—commonly used psychiatric drugs—as well as beta-blockers like metoprolol, nebivolol, and propranolol, and statins such as atorvastatin, pravastatin, rosuvastatin, and simvastatin.
The study found that mothers who were prescribed at least one SBIM during pregnancy had a 1.47-fold increased risk of having a child diagnosed with ASD. The risk was not static; it rose in a dose-dependent manner. For each additional SBIM prescribed concurrently, the likelihood of ASD increased by 1.33 times, reaching a 2.33-fold higher risk when four or more such medications were used simultaneously.
Out of the 234,971 children in the dataset diagnosed with ASD, approximately 15% had prenatal exposure to at least one SBIM. Meanwhile, the prevalence of SBIM use during pregnancy has surged dramatically, climbing from 4.6% of pregnancies in 2014 to 16.8% in 2023.
This convergence of widespread use and measurable risk has prompted researchers to characterize their findings as a “public health signal”—one that demands careful interpretation but cannot be ignored.
Why Cholesterol Matters for the Developing Brain
At the heart of the study lies a deceptively simple yet crucial biological process: cholesterol synthesis. While cholesterol is often associated with cardiovascular disease in adults, it plays an entirely different—and essential—role during fetal development.
Cholesterol is a fundamental building block of the brain, which is the most cholesterol-rich organ in the human body. It is vital for the formation of cell membranes, the development of neural circuits, and the regulation of signaling pathways that guide brain growth and organization.
During pregnancy, the developing fetus initially relies on maternal cholesterol supply. However, around 19 to 20 weeks of gestation, the fetal brain begins producing its own sterols through an intricate biosynthesis pathway. Disruptions to this pathway—whether genetic or environmental—can have profound consequences.
One well-documented example is Smith-Lemli-Opitz syndrome (SLOS), a rare genetic condition caused by mutations affecting cholesterol synthesis. Children with SLOS often exhibit severe developmental abnormalities, and up to 75% meet the diagnostic criteria for autism spectrum disorder.
This connection has long suggested that proper sterol metabolism is critical for neurodevelopment. However, until now, large-scale investigations into how medications might inadvertently interfere with this pathway—and thereby influence developmental outcomes—have been limited.
The UNMC study is the first nationwide effort to examine this relationship systematically. Its findings suggest that many widely used medications may unintentionally disrupt sterol biosynthesis, potentially altering the biochemical environment in which the fetal brain develops.
Importantly, these medications were not originally designed to target cholesterol pathways.
Their primary functions range from regulating neurotransmitters in psychiatric conditions to controlling heart rate and blood pressure. Yet their secondary effects on sterol metabolism appear to be significant enough to warrant closer scrutiny.
The researchers emphasize that this does not mean the medications are inherently unsafe. For many patients, these drugs are indispensable, providing life-saving or quality-of-life–preserving benefits. However, pregnancy represents a uniquely sensitive period, during which even subtle biochemical changes can have amplified effects.
As Dr. Mirnics explained, the findings highlight the need to reconsider how medications are evaluated for use during pregnancy—not just in terms of their primary effects, but also their unintended interactions with critical developmental pathways.
A Public Health Turning Point: Rethinking Medication Use in Pregnancy
The study’s authors are careful to strike a balanced tone. While the data reveal a compelling association, they do not establish direct causation. Nor do they advocate for abrupt changes in medication use without medical guidance.
“No pregnant patient should discontinue or alter medication without medical supervision,” the researchers stress. This caution is essential, as untreated conditions such as depression, anxiety, or cardiovascular disease can pose serious risks to both mother and child.
Instead, the study calls for a more nuanced and proactive approach to prescribing practices—one that accounts for emerging evidence while prioritizing patient safety.
Among the key recommendations put forward by the research team are several actionable steps aimed at improving drug safety for pregnant individuals:
First, they advocate for the creation of a comprehensive and publicly accessible list of medications known to inhibit sterol biosynthesis. Such a resource would enable healthcare providers to make more informed decisions when treating pregnant patients.
Second, the researchers urge that all new pharmaceuticals undergo evaluation for unintended effects on the sterol pathway. This would represent a shift in drug development protocols, integrating developmental biology considerations into early-stage testing.
Third, they emphasize the need for increased education among healthcare providers. Many clinicians may be unaware of the potential for commonly prescribed medications to interfere with cholesterol synthesis, particularly in the context of pregnancy.
Fourth, the study highlights the importance of discussing safer alternatives whenever possible. In cases where discontinuing treatment is not feasible, switching to medications with minimal impact on sterol biosynthesis could reduce risk.
Another critical recommendation is to avoid prescribing multiple SBIMs simultaneously during pregnancy whenever feasible. The study’s dose-dependent findings suggest that cumulative exposure significantly amplifies risk.
The researchers also point to the potential role of genetic susceptibility. Some individuals may have underlying vulnerabilities in sterol metabolism, making them particularly sensitive to the effects of SBIMs. Identifying these patients through genetic screening could enable more personalized and safer treatment strategies.
Finally, the team calls for continued investment in research to better understand the mechanisms underlying the observed associations and to develop interventions that can mitigate risk.
The study itself was conducted through a collaborative effort involving multiple departments at UNMC, including Pediatrics, Biostatistics, and the Munroe-Meyer Institute, as well as the
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