The findings have fuelled calls for a national entitlement of 12 days of reproductive leave.
The Bankwest Curtin Economics Centre report highlights the staggering economic toll of absenteeism, presenteeism, and career impacts linked to reproductive health issues and was commissioned by the Health Services Union, Aware Super, and the Queensland Council of Trade Unions.
"Severe menstrual pain alone costs women nearly nine productive days a year, while those experiencing menopause with severe symptoms face a 25 per cent drop in productivity," the report states.
Presenteeism, the act of working while unwell or in pain, significantly contributes to Australia's $26.6 billion annual productivity loss from untreated reproductive health issues, according to the report.
Unlike absenteeism, where individuals take time off, presenteeism often results in reduced efficiency and prolonged suffering, as employees push through severe symptoms.
Endometriosis—a condition affecting one in seven women—has had a devastating effect on women's careers, with one in three forced to change jobs, forgo promotions, or switch career paths due to debilitating symptoms.
"Endometriosis is not just a health issue; it's a career issue," said the Health Services Union's national senior assistant secretary Kate Marshall.
"This powerful research exposes the financial impact of ignoring reproductive health.
"The $26 billion annual cost isn't just an abstract number — it reflects real lives disrupted and real productivity lost."
The report estimates implementing 12 days of paid reproductive leave for all Australians would cost employers $920 million annually — just a fraction of the cost of inaction.
Ms Marshall described the proposed leave as a win-win solution, reducing absenteeism, improving productivity, and enabling workers to manage their health with dignity.
"Providing access to paid leave will allow people to rest, heal, and treat these conditions without worrying about financial and workplace consequences," she said.
Reproductive leave would cover conditions such as severe menstrual pain, menopause, endometriosis, IVF treatments, vasectomies, gender transitioning therapies, and other reproductive health issues.
The Health Services Union is campaigning for the entitlement to be included in the national employment standards, which set minimum conditions for Australian workers.
If implemented, it would make Australia a global leader in reproductive leave policy.
Health and Community Services Union Victorian secretary Paul Healey said the proposal would revolutionise workplace equity.
"Reproductive leave would be a game-changer for Australia and a world first because we are pushing for the 12 days to be available to all genders," Mr Healey said.
"Too many people are draining other types of leave to deal with their reproductive health.
"Every worker, regardless of their reproductive health challenges, should have the best chance to stay at work."
The report points to success stories abroad, noting that reproductive leave policies in countries including Japan and Italy have reduced absenteeism and staff turnover.