By Syreen Goulmamine, MPH, CHES®, SWHR Programs Manager
Why Clinical Trials Matter for Women’s Health
Clinical trials are the foundation of evidence-based medicine, generating data that determine how diseases are diagnosed, prevented, and treated. From establishing medication safety and dosing to shaping clinical guidelines and standards of care, trials influence nearly every aspect of modern health care.
Yet for this evidence to be truly reliable, the populations studied must reflect the populations served. Women’s health outcomes are dependent on inclusive and representative research. Factors like biological differences and hormonal changes across the life course can influence disease risk, symptom presentation, and treatment response. When women are underrepresented in research or when data are not meaningfully analyzed and reported by sex and other key demographic factors, the resulting evidence can overlook critical differences, leading to gaps in care and less effective treatments.
Meaningfully including women in clinical trials is not simply a matter of fairness, but it is also a scientific imperative to improving health outcomes for over half the population.
A Brief History of Women in Clinical Research
For much of the 20th century, women, especially pregnant and reproductive-age women, were systematically excluded from clinical research, creating profound gaps in the evidence base guiding their care. In 1977, the U.S. Food and Drug Administration (FDA) issued guidance effectively barring women of “child-bearing potential” from early-phase drug trials in response to a research tragedy related to thalidomide, a drug used to treat morning sickness. Although intended to protect infants from harm, this policy normalized women’s exclusion from trials. For many years, we had very little information about how medicines affect women differently, including how their bodies process medications, the right doses to use, possible side effects, and long-term health outcomes.
As a result, many therapies were approved and prescribed without adequate understanding of how biological sex, hormonal status, pregnancy, or life stage might alter their effectiveness or safety. This further contributed to adverse drug reactions and poor treatment for women.
The 1990s marked a turning point in federal policy and advocacy. In 1990, the National Institutes of Health (NIH) established the Office of Research on Women’s Health (ORWH) to elevate women’s health research within the federal government. That same year, the Society for Women’s Health Research (SWHR) was founded to champion the inclusion of women in biomedical research and to advocate for structural reform. The NIH Revitalization Act of 1993 mandated the inclusion of women and minorities in all NIH-funded clinical research and required analysis by sex, race, and ethnicity, strengthening the authority of ORWH and the then Office of Research on Minority Health (ORMH), which ultimately became the National Institute on Minority Health and Health Disparities (NIMHD). The FDA followed by creating its Office of Women’s Health in 1994.
More recently, policy efforts have focused on moving beyond inclusion toward analysis and accountability. NIH’s 2016 Sex as a Biological Variable (SABV) policy requires investigators to consider sex in study design and reporting. In 2016, specific FDA guidance (FDA-2016-D-3561) standardized the collection of race and ethnicity data in clinical studies and clinical trials, and was later updated in 2024; a set of FDA guidance from 2020 (FDA-2019-D-1264) addressed eligibility criteria and trial design barriers to diversity; and FDA guidance issued in 2022 and 2024 (FDA-2021-D-0789) introduced Diversity Action Plans to improve enrollment of underrepresented populations in clinical studies. Despite these advances, meaningful inclusion remains uneven.
Where We Are Now and Gaps in the Current Landscape
Women do not always have equal access to clinical trials. Many barriers, including structural, scientific, and social, limit their participation. On a structural level, research funding priorities, strict eligibility rules, and the long history of excluding pregnant and breastfeeding people have reduced the amount of evidence we have about women’s health. Practical challenges also make participation difficult. Many women have caregiving responsibilities, rigid work schedules, or limited access to transportation and childcare. These barriers especially affect low-income women and women from marginalized communities. In addition, trust remains a major issue. Past exploitation, ongoing underrepresentation, and limited community engagement have led some women to feel hesitant about joining research studies.
Furthermore, despite increased regulations related to the inclusion of women in clinical research, important gaps still limit progress in sex-specific and gender-responsive science. Much research still relies on male-focused animal models and does not fully consider hormonal changes, reproductive stages, or differences in how medications work in women’s bodies. Important life stages are often overlooked. For example, girls are underrepresented in pediatric research due to ethical and consent challenges, which limits what we know about how female puberty affects health. Pregnant and postpartum individuals are often excluded from clinical trials, even though pregnancy can reveal important long-term heart and metabolic risks. Menopause and midlife transitions are also rarely studied, despite major hormonal and metabolic changes during these years. As a result, we miss key information about how these natural changes impact women’s long-term health, particularly cardiovascular, neurologic, and metabolic risk.
Although regulations have increased the inclusion of women in clinical research, important gaps still limit progress in sex-specific and gender-responsive science. In several major health fields—such as cancer, neurology, kidney disease, and heart disease—women are still underrepresented in research compared to men and compared to their disease burden. Even when overall participation numbers look balanced, many studies are not designed to intentionally analyze differences between men and women. As a result, researchers may lack clear evidence about differences in treatment effectiveness, appropriate dosing, and potential side effects for women versus men. Together, these gaps weaken precision medicine, widen health inequities, and place avoidable strain on health systems.
What Equity-Centered Clinical Trials Can Look Like
Inclusive clinical trials must move beyond passive acceptance toward intentional co-creation with women across diverse backgrounds, ensuring research questions, outcomes, and protocols reflect lived realities. This means integrating women from across the life course into study design and analysis, which will help ensure that the physiologic transitions and social contexts that shape health risks and treatment responses are accounted for. Standardized reporting requirements for sex- and gender-based analyses—including analyses that also consider race, ethnicity, and other social factors —should be built into research as core methodology rather than as optional. Policy frameworks, funding agencies, and research institutions play a critical role in driving this shift by aligning grant criteria, regulatory guidance, and infrastructure investments with equity goals, such as supporting decentralized trial models, caregiver accommodations, and community-engaged recruitment strategies. Finally, strong accountability measures are essential. To begin, journals and regulators should enforce publication standards that require data to be reported by sex and other key demographics and require clear explanations for any exclusion. For funders and sponsors, they may consider linking their support to inclusive study design and clear, transparent reporting. Together, these approaches ensure that equity is treated as a measurable component of scientific rigor rather than a secondary goal.