Calls Grow for More Female-Focused Medical Trials in the UK

New analysis reveals a significant gender imbalance in UK clinical trials, raising concerns over gaps in medical evidence for women.

Health experts have raised alarm over the under-representation of women in UK medical research, following new data showing that male-only clinical trials outnumber female-only trials by 67%. The imbalance, described as “concerning,” highlights persistent disparities in how research is conducted—and who it benefits.

A dataset of 4,616 clinical trials submitted to the Medicines and Healthcare products Regulatory Agency (MHRA) between 2019 and 2023 was analysed by the University of Liverpool. While most trials (90%) included both men and women, 6.1% involved only male participants, compared with just 3.7% that focused exclusively on females. Even more striking, pregnant and breastfeeding women were involved in only 1.1% and 0.6% of trials respectively.

Experts say the lack of inclusion means women and healthcare providers are frequently forced to make treatment decisions without adequate clinical evidence.

“A Vacuum of Evidence”

Dr Amy Brenner, assistant professor at the London School of Hygiene & Tropical Medicine, said the data was troubling.

“It is particularly concerning that there are more male-only trials than female-only trials, as it is certainly not the case that more conditions affect men exclusively,” she said.

This disparity has significant implications for treatment efficacy and safety in women, Brenner noted, adding that the limited participation of pregnant and breastfeeding women—often excluded for safety reasons—further exacerbates the evidence gap.

“Without trials involving these populations, women will continue to miss out on potentially beneficial treatments,” she said.

Consequences for Women’s Health

Reproductive health and childbirth trials accounted for only 2.2% of total studies, despite the pressing need for treatments targeting pregnancy-related conditions. Professor Anna David, director of the EGA Institute for Women’s Health at University College London, said this lack of focus contributes to a stagnation in women’s health innovation.

“There is a perception that women, particularly those who are pregnant or breastfeeding, don’t want to participate in clinical trials,” David said. “This is not the case. The result is that women and their doctors are forced to make choices in the absence of reliable data. That is not ethical.”

David also pointed to the lack of treatments for conditions such as pre-eclampsia and placental insufficiency as a consequence of this research neglect.

Gaps in Broader Medical Research

While cancer research dominated the trial landscape—comprising nearly one-third of studies—other leading health issues were significantly underrepresented. Heart disease, the world’s biggest killer, accounted for just 5.2% of trials. Research into chronic pain, respiratory conditions, and mental health also lagged behind, despite their broad public health impact.

Older adults, by contrast, were well represented: 67.7% of trial participants were aged 65 or above.

Innovative treatments, including gene and cell therapies, are gaining ground but still comprise only 3.4% of UK trials.

Efforts to Address the Imbalance

Professor Andrea Manfrin, deputy director of clinical investigations and trials at the MHRA, acknowledged the imbalance and the need for change.

“When specific groups are not adequately represented, it creates evidence gaps about how medicines work for them,” she said. “Increasing diversity in clinical trials is a priority for the MHRA.”

To that end, the agency is collaborating with researchers, sponsors, and ethics committees to improve trial design and inclusion.

Dr Brenner also emphasised the importance of involving women in shaping the research itself. At LSHTM, patient and public input is integrated into trial planning from the outset. “Ensuring strong representation from women in these groups is key to understanding barriers and improving participation,” she said.

Political Support for Reform

Health minister Karin Smyth said the government remained committed to making the UK a global leader in life sciences, with an emphasis on conditions most affecting patients.

Science minister Lord Vallance echoed the sentiment, saying: “We must ensure that trials of new medicines are available for everyone to take part in.”

As health leaders call for systemic changes in how research is designed and funded, the evidence highlights a growing need to close the gender gap in clinical trials—ensuring women are no longer left behind in medical innovation.