**Why Pregnant People Are Often Excluded from Drug Safety Studies—and Why That Needs to Change**
Despite the widespread use of medications during pregnancy, there remains a significant lack of clinical research focused on drug safety for pregnant individuals. This gap leaves both patients and healthcare providers navigating treatment options with limited and sometimes unreliable information. A recent discussion featured in *Scientific American* sheds light on why pregnant people have historically been excluded from drug trials, the consequences of this exclusion, and the urgent need for change in how we study medications during pregnancy.
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### The Controversy Over Acetaminophen and Autism
The conversation around medication safety during pregnancy recently gained renewed attention when former U.S. President Donald Trump and his health secretary claimed that acetaminophen (commonly known as Tylenol) use during pregnancy and early childhood might be linked to autism in children. This announcement sparked concern and confusion among many pregnant people and parents because it contradicted the prevailing medical consensus.
However, experts emphasize that this claim is not supported by robust scientific evidence. The studies cited to suggest a link between acetaminophen and autism rely on correlations that do not account for confounding factors. For instance, acetaminophen is often used to treat infections during pregnancy, and some infections themselves have been associated with autism. These overlapping variables complicate any direct conclusions about the drug’s safety.
In reality, acetaminophen has been widely prescribed and used safely for decades. It remains the preferred option for pain and fever relief during pregnancy, especially compared to alternatives like ibuprofen, which is known to carry actual risks to the fetus. The controversy highlights a broader problem: the lack of comprehensive, evidence-based data on medication use in pregnancy leaves many pregnant people without clear guidance.
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### The Historical Roots of Exclusion from Clinical Trials
Why is there such limited data on drug safety in pregnancy? The answer partly lies in historical events and resulting regulatory decisions. The thalidomide tragedy in the 1950s and ’60s serves as a pivotal moment. Thalidomide was a drug prescribed to alleviate morning sickness, but it was later discovered to cause severe birth defects in thousands of children. This disaster led to increased drug regulation and stricter safety requirements.
While these changes aimed to protect patients, they also led to pregnant people being categorized as a “vulnerable” population incapable of providing informed consent for clinical trials. Consequently, pregnant individuals were largely excluded from drug safety studies. This exclusion was intended as a safeguard against harm but paradoxically resulted in a lack of knowledge about the effects of many medications during pregnancy.
Today, this legacy persists. Despite the fact that as many as 80 to 90 percent of pregnant people take prescription medications, fewer than 1 percent of clinical trials include them. The healthcare system, in trying to protect pregnant people from research risks, has instead left them and their healthcare providers to make decisions based on incomplete information.
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### How Medication Safety in Pregnancy Is Studied Today
Given the exclusion of pregnant people from many clinical trials, how do researchers study medication safety in this population? There are several approaches, but each has limitations.
One common method is **observational studies**. These studies examine pregnant people who are already taking certain medications, often because they have chronic health conditions such as diabetes, heart disease, or infections like HIV that require ongoing treatment. By observing outcomes in these cases, researchers can infer potential risks or safety signals related to drug exposure.
Another approach compares pregnancies within the same individual—looking at cases where a person took a particular medication during one pregnancy but not another. This helps control for genetic and environmental factors that might otherwise confound results.
Preclinical studies, including animal testing and trials in nonpregnant humans, also provide foundational safety data before a drug is used in pregnant populations. However, animal models do not always perfectly predict human outcomes, and nonpregnant human data cannot fully address pregnancy-specific effects.
Despite these tools, the fundamental challenge remains: without including pregnant people in **randomized clinical trials**—the gold standard for assessing drug safety and efficacy—our knowledge remains limited. Experts argue that excluding pregnant people from research denies them the opportunity to benefit from evidence-based care and leaves them vulnerable to unknown risks.
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### Balancing Risks: The Case for Including Pregnant People in Clinical Trials
The fear that clinical trials might harm fetuses has been a major reason for excluding pregnant people from research. However, experts emphasize that the risks of not studying drugs in